Conference vmszoo::rc

    world engines makes a 7 channel box (called the expert) that supposedly
    meets 1991. Indy Hobby sells them for ablout $150. I have one on
    order, due in in about 10 days. Will let you know when it comes
    in or you can call Indy and find out
    
    md

    frank
         POLK sells a seven channel radio 1991 ready for $117.00 IT
    IS ADVERTIZED IN RC MODELER. TAKE A LOOK AT THE ADD, IT MIGHT BE
    WHAT YOUR LOOKING FOR.
    
                                     COLIN
    

    
         I'm reading this note and I'm getting concerned!  Does this
    mean by 1991 all 72 mhz radios will be shelved?  Exactly what will
    happen to our radios of today?  Will anything be mandatory or by
    law, illegal?  I've got a Futaba Conquest 6 channel, and would hate
    to get rid of it just because I'm on the 72 mhz band!  So what are
    my choices?  Could I just change the crystals?
    
    Confused!!!!

I think that the Royal receiver is very similar to the
ACE Digital Commander.  That receiver is still supported, though
not as a choice product, by ACE.

I'm hoping that by 1991 ACE will have come out with its new
receiver.  Its supposed to be very close now; I think they're
just hedging their bets for some new developments in technology.
You can be sure that it'll be a good one, and reasonable.

I don't know if the earlier notes pointed this out.  Supposedly,
the existing transmitters will be legal in 1991.  Probably most
of us should send our transmitters in before then and have them
checked.  This last MA had a comment that more shops are getting
spectrum analysers in anticipation of the new requirements.  Its
the receivers that will have to be replaced.  But, of course,
as long as you're radiating correctly (your transmitter's
ok), the FCC could care less about your receiver.  Just that if
you get shot down because of a pager on an adjacent channel,
don't cry.  From what I hear, they don't care too much if you're
legal either...we're considered a secondary user.

The enforcement will come from the AMA; I don't know how they
will assure that only 1991 receivers are used for competition.  I
suspect they'll just check the transmitters.  I also suspect that
most of the clubs (unless you're unfortunate enough to have one
of the AMA frequency committee) will look the other way with
regard to the equipment you're using.  We're all in the same
boat, after all.  That leaves the Nats as the only way that the
AMA can enforce the 1991 rules.

    Just got my EXPERT 7 Channel yesterday, after the six week wait
    I was promised by INDY.  Looks to be very well put together, has
    a good "heft", and feels good.  We'll see how well it flies perhaps
    this weekend!
    
    The specs don't mention 1991, but Indy says it is.  However, the
    literature shipped with the radio says it can fly 10KH spacing between
    another you and another pilot!  I don't know if I believe that,
    but even if it was twice that, it would be OK for 1991.

    Just a note on 10KH spacing...
    		In the UK all our 35meg equipment is tested and used
    on 10KH spacing although most clubs and competitions ask for 20KH
    spacing.
    
    	We currenty have 20 channels numbered from 69-80 and are expecting
    soon the approval of 5 or 6 more at the top end. 
    
    	One further comment... I think our rules here differ about the
    changing frequecies... our transmitters and recievers are fitted with
    externally accessable sockets which enable us to change frequency
    easily.. provided you can afford the expence of extra crystal pairs.
    
    			Trev.

    About FCC interest:
    
    As I understood it, it's the other way around. FCC has already
    allocated ALL the channels. It's the AMA that has restricted usage
    to even numbered channels only until 1991, to allow people to upgrade
    their radios to narrow band. My guess is that the 1991 phase in
    will take place over a few years - clubs with a lot of people who
    have the wide band gear may just forbid odd channel operation at
    their field. 

    Glad I'm a ham...
    Dave

    re .103:  
    Dave,
    	After we experienced all of the crouds yesterday, it is obvious
    to me that the last thing we need is more frequencies.  Since our
    club has an agreement (loose rule) that only four planes shall be
    airborne at one time, there is really no reason to have 50 frequencies.
    I would bet that one thing that will happen is that many clubs will
    group at least the two adjacent odd frequencies on a pin to keep
    the spacing of all operating transmitters at 40Khz like it is now.
    Until all of the equipment has proved reliable at 20Khz spacing,
    I think that this is a good idea.
    
    Charlie
    

1991 is only for the USA.

The previous note that talked about bandwidth brought me up
short.  I realized that I was making assumptions about bandwidth
that were possibly not true.  This weekend I looked up the series
of articles on the new plan that were published in MA June
through August this year.  Found out that I have spread some
misinformation.

It turns out that in the RC band, there are Public Service users
spaced on the even 20 KHz segments.  We are occupying a 10 KHz
bandwidth centered at the borderline between two PS stations.
That is, if there is a PS station at 72.660, and one at 72.680,
we have the section between the two, at 72.670; channel 44.  What
the AMA article didn't explicitly say, but I believe is true, is
that the PS stations can use the full 20 KHz bandwidth, and if
they interfere with us we must get out of the way.  We, in turn
use only 5 KHz on either side of center; our frequency therefore
is part of the PS sidebands.  The thing that the AMA got in
compensation for that is the large number of channels.  If they
interfere, we should go to another channel.

We are considered secondary or interdistal users; that is we
occupy the space between two primary users, and are responsible
for not interfering with them.  If we shoot a pager down (hardly
likely), we must get off the frequency.  If a pager shoots us
down, we must gather our wreckage and go to another frequency.

That's the way I understand the articles; if I'm wrong, please
let me know!  I still believe that the implication of this is
that since we're always wrong under interference, the AMA will
have a hard time not paying on an insurance claim; they will
never be able to say conclusively that you were not interfered
with by a PS user.  This is, I think, why no insurance carrier
will cover the AMA; there is no way they can contest a claim and
win.

And again, tests on transmitters already existing in the field
show that most of the good ones are legal by 1991 standards.

Getting back to the original topic of this note (and, I apologize
for such a digression), we were talking about buying equipment at
this time.  I think that if you did buy non-1991 equipment, you
could probably still look to having 5 or so years from it, unless
you were participating in AMA sanctioned events ( or unless your
club has a member of the AMA Frequency Committee in it!).

I think that essential features of 1991 equipment are narrow
bandwidth, some method of easily changing channels (that is the
future), and possibly PCM.  These things will be the norm in 5
years, and expensive equipment that you buy now should have them
too.   You will not be able to exist in a post-1991 environment
without channel changing. 

    Our current equipment will not work if there is an interfering source
    of any significant magnitude only 10Khz away!  As I understand it,
    if that happens, you must find another frequency to use.  If a
    particular flying site has an interfering source, some frequencies
    may be unusable at that site.  It is a good idea to talk to some
    knowledgable club members before selecting a frequency for this
    reason and also to try to pick a frequency that is not over crowded
    at that field already.  Strong TV transmissions (I think CH4) can
    interfere with certain RC channels as well.  If your field is near
    a tower, find out if anyone is having trouble with any particular
    frequencies.  
    	It is true that the receiver is the key element in eliminating
    interference to your aircraft's control by other closely spaced
    properly working transmitters.  However, if your transmitter is
    not in spec, you could be splattering into adjacent channels and
    causing others grief.  Your receiver can only reject frequencies
    different from your own.  The narrow band dual conversion receivers
    have sharper filters to better reject adjacent channels. 
    Charlie
    

    John/Chris,
    
    I'm sure the subject has been spoken to more than once or twice
    in the past but I rechecked the current issue of MA just this morning
    and Meyers discusses [revisits] the 1991 AM/FM/PCM issue(s) in the 
    Radios Techniques column of this issue.      
    
    Adios, 	Al

    I did some checking this summer, and none of the Futaba PCM sets
    are 1991 approved!  I believe that the main problem is the receiver
    selectivity and not the transmitter spectrum.  I don't think that
    any of the AM receivers are narrow band.  Dual conversion receivers
    seem to be required to meet the selectivity specs.
    
    Charlie
    

re: .21 - George Meyers talked about that one too, some months
back.  He was discussing the sanctions that the AMA can exercise
against the manufacturers to force them to comply with 1991 --
since, as discussed previously, the FCC couldn't care less about
receiver design.   The bottom line was that as of now, aside from
publishing test results, the AMA could do nothing -- and they are
reluctant to publish unfavorable test results because of
advertising revenue.

I'm sure that manufacturers like Futaba will try to milk the
most out of their current design in terms of sales payback as
they can.   Perhaps the best policy is to wait on new equipment
until the manufacturer's take a definite stand. 

As I've remarked earlier, Tower does not make a big deal of
mentioning that a particular radio meets 1991; I suspect that
they are protecting their sales too.  

    
    		When I purchased my Futaba 6FGK last year (1986) they,
    	Futaba, claim that it also is dual conversion.
    
    			Mike
    

    Remember:  As Charlie said, it's unlikely that a receiver will meet
    1991 specs if it isn't dual conversion. But, that doesn't mean that
    any dual conversion receiver meets 1991 specs!!!!!
    

    Just received word that my radios are ready after having their
    frequencies changed to the new channels...price tag: just over $100
    (which included one complete new battery set, a charger cord and
    3-sets of the new, improved{?}/worthless frequency flags).  It's no 
    longer possible to glance at the flightline and determine what freq's are 
    in use; _everyone's_ on red, or so it seems...you must get within reading
    distance before you can make out what channels are on - stupid!
    
    <FLAME ON>  I just have to thank the AMA (facetiously) ever so
    kindly for creating such a frequency mess over the protests and
    better advice of so many knowledgeable R/C radio experts and for
    forcing me to "fix" two radios which weren't broken in the first
    place!  Those of you new to the hobby/sport/recreation may not be
    familiar with the days before terms like "narrow-band," "third-order
    intermodulation," etc. had been coined or even thought of but, in
    those happier/simpler days, the radio atmosphere was nowhere near
    as harrowing or threatening as it is today AND IT COULD GET WORSE! 
    
    If, as was the original plan, the odd-numbered channels, e.g. 39,
    41, 43, etc. are dumped upon us, flying fields will begin to resemble
    demolition-derby sites!!  Several experts (Jack Albrecht of Airtronics,
    Steve Helms of Futaba, Ted White, Jim Odino among them) have told
    me in so many words that the technology to build a reliable,
    "affordable" 1991 radio does not exist, regardless of the claims
    of some manufacturers.  Albrecht states (and I sincerely hope he's
    right) that the odd-numbered channels may  never come to be due
    to the lack of "true" narrow-band technology for our application.
    
    The primary point in my personal view is simply this:  Why in the
    H*LL do we need 40-50 frequencies at the cost of all the negative
    ramifications?  10 would be more than enough for any field, competition
    or event I've ever seen...10-planes in the air at once are about
    5 too many in the first place!!  We were "_FAR_" better off with
    the original 72Mhz frequencies than we are today or are likely to
    be in the future!!!!!!!!!!!!!!  <FLAME OFF> (but not really) 	 

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    Al,  As I can understand your frustration in having to fix what
    wasn't broken I cannot agree that on the whole we were better off
    with the old frequencies.  Granted that the adition of the new
    frequencies have caused some problem to forseen but then again you
    don't have to share your frequencies with any beepers or repeaters
    now a days.  I had read something a while back that indicated that
    new naoorw band spaced radios were only to be issued for the new
    channels below 38. I thought that they were going to leave the higher
    channels alone even after 1991.
    	As far as the frequency flags go Al, the red ribbon with
    white/black frequency identifier is only manditory at competitions.
    If a club so chooses they can use the colored flags or black on
    white or any comnibation of both. We in the PVRCC do just that.
    We have not made it manditory for any flyer to go to the red ribbon
    identifiers. The only thing we stress is that if you use the red
    ribbon white/black method that your frequency pin for the frequency
    board correspond. 
    
    
    						Tom

    Hey! Looks like I managed to stir up some interest here...great!
    Now for some responses:
    
    Re: .755 & .759:  Price of R/C systems is not a real issue with me.
    My first radio was an almost-used-up F&M 4-ch. proportional rig
    with only 3-trimmable channels; this rig cost me nearly 500 1963
    dollars so I agree that today's radios, with today's advances and
    today's prices are a bargain, no matter how you slice it.  My ire
    is a principle-thing; being required to make a change to a perfectly
    functional radio for no demonstratably good reason.  Also, I have
    to agree with Bill that it'd be awfully easy for me to believe in
    a conspiracy between the AMA and the radio mfgr.'s to obsolete older
    (but perfectly good) radios, require updating of the rest and/or
    necessitate purchasing a new system.
    
    Re: .756: Yer' right Bill, I never considered the problems of those
    with color blindness...sorry 'bout that.  However, it's not the
    black-on-white channel number I object to; it's the absence of the
    color-coded flags, unique to each channel/frequency...we coulda'
    had the best of both worlds, but noooooooo.........
    
    Re: .758: Tom, My understanding is/was that narrow-banding is required
    immediately for all new channels below ch. 38 but, after 1991, _all_
    channels will require narrow-banding to accomodate the inclusion
    of all the odd-numbered channels which will create 10Mhz bandwith/
    separation across the board.  Our only hope to see it otherwise
    is if the AMA wises up to the lack of need for so many channels
    and holds off on releasing the odd-numbered channels. I stand ready
    to be corrected if this is not correct but this is what my radio
    guru confirmed when I picked up my radios last night.  Incidentally,
    I guess it's a personal thing as to whether we're better off or
    not today...I for instance, feel we were better off choosing
    frequencies known not to have pager and other users on them than
    to have a situation where we'll have these same people mixed among
    our channels a mere 5-10Mhz away.  Also, 3IM was unheard of before
    the _new-improved_ system was initiated...I'd opt for the old system
    in a heartbeat.
    
    Re: .760: All numbered channels, e.g. 38, 40, 42, etc. are the "new"
    1991 channels and will be legal subsequent to then _IF_ they meet
    the narrow-banding specs that will be required when/if the odd-numbered
    channels, e.g. 39, 41, 43, etc. are released.  All citizen's band
    frequencies (27Mhz band) remain legal (WHOOPEE!) but we'd be fools
    to use them.  Also, all 6-meter HAM frequencies remain legal though
    I'm told the A.R.R.L. recommends changing to specific frequencies
    other than those currently in use to get away from repeater frequencies.
    
    Re: .757:  No, you won't hear much "God's country" rhetoric from
    me now 'til about late September when it starts cooling off again.
    Meantime, this is more like "Satan's country," regarding the tem-
    peratures we put up with...I just consider summer the price I must
    pay for the gorgeous fall-winter-spring we [usually] have.  On the
    3IM incident, it's interesting that Charlie was the victim on ch.
    46.  According to my calculations, the channels that _should_ have
    been susceptible to 3IM with the frequencies you mention in operation
    are: 36, 44 and the guy on 48...weird.  Will your system work? 
    Who knows?  I still think it's all F.M., myself ;B^} .  I know that
    our local frequency separation people believe that the bigget
    preventative to 3IM is a 30' minimum separation between transmitters.
    All our fields run 5-flight stations, 30' or more apart and, except
    in contest/event situations, no consideration whatever is given
    to frequency sorting...you can fly from any station you prefer.
    Thus far, 3IM seems to be a rarity using this setup...one field
    _does_ use a freq.-to-flightline sorting system but they are no
    more immune to the problem than the fields which do not.
    
     

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

Actually, as I've pointed out before, the frequency separation
between adjacent RC channels remains at 20 KHZ.  What does change
is that there are pager frequencies allocated between each RC
channel, thus our requirement for 10KHZ bandwidth.  That's what
an "interdistal" user is; one who occupies a frequency between
two other frequencies.

Now, here's the kicker; an interdistal user is a  "secondary"
user for the frequency.  The AMA bought into this because,
aside from the fact that they had little choice, it opened up
numerous channels to our use.  That's the part the AMA tells us
in a loud voice. Here's the part they whisper about; if a pager
shoots you down, you are at fault. 

Your responsibility is to use the numerous channels to find a
clear frequency.  But wait; there's more: Suppose you hurt
someone in being shot down.  First of all it will be difficult to
prove that an adjacent pager did not shoot you down, even if it
would do you any good, as I'll explain later.  But anyone
operating on a frequency adjacent or on your frequency could've
done it. 

If there's a pager nearby, its your fault for operating there,
irregardless of the quality of your radio, 1991 or not.  And even
if there's no pager, any smart lawyer can find an engineer to
testify that the 72 mHz band is subject to "skip" from distant
legally operating pagers.  And you will be liable because you're
a secondary user. 

Another feature of being an interdistal user is that the pager's
sidebands can legally infringe on your signal.  Your sidebands
cannot infringe on the pager's.  This is why we must go to narrow
band transmitters.  An adjacent pager can therefore shoot you
down LEGALLY, because you're not supposed to be there, and you're
liable for all damages. 

So, if you're shot down and hurt someone, its your fault --
If you're shot down for *any reason* you cannot prove
that it was an illegal transmitter, or any other cause in court.
Even if the pager did it, you're still liable.

Or rather, you, in the shape of the AMA will be liable.  That, I
believe is the real reason why AMA cannot find an insurance
carrier; the case will always lose. 

If anyone can prove me wrong on this one, I'd sure be happy!

The europeans operate on 5 kHz bandwiths, that could be true.
But they don't have multi-kilowatt adjacent stations to contend
with!

Lastly, DON'T even begin to consider a 1991 radio that doesn't
allow you to rapidly change channels.   I like the Airtronics
module series.

    After reading 27 replies to this topic, I'm still not sure of the
    conclusions contained herein.  Also, this topic was created some time
    ago and the information may be somewhat out of date.  Since I'm
    relatively new to RC aviation, and am quite interested in acquiring a
    _quality_ radio that has _both_ the Tx and Rx in line with 1991 specs,
    I was wondering if anyone has some conclusive information concerning
    the availability or existence of such animals.  I won't say that money
    is no object, but I am willing to spend the money for a radio that
    won't be outdated in two short years.
    
    Is JR's new PCM 10 applicable to 1991?  How about the new Futaba PCM
    1024's?  Has anyone seen anything but list prices for either?  How
    about availability?

    Actually, I was thinking more alnog the lines of JR's Century PCM ...
    Is the "ABC & W Dual Band conversion reciever" (what a keyboard-full
    :-) ) more than just that.  Would anyone recommend that radio, or
    should I go up to the JR Galaxy series?

    Don

    I have a JR century and a JR Galaxy radio.  The Century is not the
    1991 version, and is FM instead of PCM.  However, it is very
    similar to the PCM in layout, etc.  I do fly a chopper, so what
    I feel may be biased that way.  The first question was "is the
    ABC&W equal to 1991 requirements?", reading from the Circus
    catalogue, "JR's ABC&W (Automatic Blocking Circut and Window)
    circuitry gives you unbeatable performance and reliability along
    with a pantented design that goes beyond 1991."  Your next question
    is "Should you spend the extra for the Galaxy?"  I have both and
    I like the program capability of the galaxy and also the fact that
    I can set the Galaxy up for more than one chopper.  However, I also
    feel that the Century is a very fine radio, and very easy to set
    up for a chopper.  I am not sure what you are looking for, so I
    would say it depends on how much those two features mean to you.
    As far as performance, they both work very well, and I have been
    very happy with both of mine.

		________
	 /	  __|__  
	=========[_____\>
	/	__|___|__/  BREAK A BLADE,
			    Ken    	

>< Note 105.28 by SMART5::DHENRY "Don Henry - FXO" >
>                        -< Did I miss something here? >-
>
>    After reading 27 replies to this topic, I'm still not sure of the
>    conclusions contained herein.  Also, this topic was created some time
>    ago and the information may be somewhat out of date.  Since I'm
>    relatively new to RC aviation, and am quite interested in acquiring a
>    _quality_ radio that has _both_ the Tx and Rx in line with 1991 specs,
>    I was wondering if anyone has some conclusive information concerning
>    the availability or existence of such animals.  I won't say that money
>    is no object, but I am willing to spend the money for a radio that
>    won't be outdated in two short years.
>    
>    Is JR's new PCM 10 applicable to 1991?  How about the new Futaba PCM
>    1024's?  Has anyone seen anything but list prices for either?  How
>    about availability?
>
>    Actually, I was thinking more alnog the lines of JR's Century PCM ...
>    Is the "ABC & W Dual Band conversion reciever" (what a keyboard-full
>    :-) ) more than just that.  Would anyone recommend that radio, or
>    should I go up to the JR Galaxy series?
>
>    Don

Things are simpler than you think.  The correct answer is posted every
month in your AMA magazine.  There is only one Vendor who has passed the
independent laboratory tests for 1991 compliance - Airtronics. 

The monthly AMA magazine lists which Airtronics Transmitters and Receivers
have passed this test.  We all believe that several other vendors are producing
1991 complaint sets but only one has proven it by the rules established 
by the AMA.

If you want a guaranteed 1991 radio Airtronics is your only choice.
As consumers we should use our purchasing power to force Futaba, JR, ACE,
etc. to get off their buns and spend the bucks to get their sets tested
by independent labs (maybe they are trying and failing - who knows).

Vote with your wallet.  I have 3 radios (AM Futaba Gold, FM Futaba Gold,
and JR Century 7 SS) but if I was purchasing a new radio today - it would
be Airtronics.

As an aside I have a list of test reports done by George Steiner
(he writes the Radio column for one of the RC magazines (forgot which
one).  Anyway he stated in his column that he had been testing various
radios in his lab and would send the results to anyone who wanted and
sent him a SASE.  I did and I made 25 copies for the DECRCM meeting tonight.

I will send a copy to anyone who sends me mail at Tallis::Fisher.  But
before you bother let me say that they are very hard to read and understand
and there is a mixture of tests of very old stuff and very new stuff and
probably not the specific radio you are interested in.  A lot of hand
scribbling and some questionable test ranking.  I would have typed the
report in as a note if it wasn't so hard to do without fear of misquoting
George's findings.

Bottom line = AIRTRONICS

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Perhaps the "ABC&W ...goes beyond 1991", but I believe that Airtronics
    is still the only company that has been "approved" by the AMA. 
    
    Each month in "Model Aviation" there is a list of 1991 conformance
    radios.  If you are planing to buy a radio in the near future, it
    would be worth reading that page.
    
    I'm not saying that the other radios do not conform, but it does
    make you wonder if the AMA does not list them...
    
    jeff
    

I just wanted to add that when you buy a radio, be sure it says
that its 1991 on the box.  Not all Airtronics are 1991.  The one
that has caught my interest is the Vanguard 6 channel FM VG6DR.
There's a big ad for it in Model Builder this month, and probably
in the other mags.

Speaking of mags.  I subscribe to Model Builder.  Last month I
didn't receive my issue -- at first I wasn't concerned, since
they often put out the December and January issues late.  While
in Phlyin Phil's shop a couple of weeks ago there was the
December issue, and it had a cover that would do credit to RC
Scale Modeller: a very pretty lady in a very revealing bathing
suit. When I called MB to order my lost issue the lady commented
that they lost a lot of the December issue in the mail.  Got my
issue Friday, they sent it in an envelope!

    Although I'm brand-new to R/C (just picked up a used Cricket helicopter
    and am looking for a radio setup) I'm reading as much as I can and
    couldn't help but notice the following:
    
    re: .30
    
>    The monthly AMA magazine lists which Airtronics Transmitters and
>    Receivers have passed this test.  We all believe that several other
>    vendors are producing 1991 complaint sets but only one has proven it by
>    the rules established by the AMA. 
>
>    If you want a guaranteed 1991 radio Airtronics is your only choice. 
 
    A Sheldon's Hobbies catalog I have in front of me shows that not
    only are NOT ALL Airtronics units rated "1991 compliant", but that
    there are models from Aristo-Craft and World that ARE.  (Futaba seems
    to be the only one conspicuously lacking ANY.)
    
    -joe tomkowitz

    I have also noticed that there is a lack of adds claiming true 1991
    compliance.  Airtronics took the lead and had an independent testing
    lab test their radio systems and all of their new designs are now
    listed as compliant.  I have a feeling that many other systems now
    being sold will also pass when they are tested.  I would also
    buy Airtronics if I needed a system and I hope that the other
    major manufacturers follow suit.
    
    Charlie
    

    I have gotten to be real good friends with a guy who runs one of
    the local hobby shops where I live.  I am in the market for a new
    heli radio and he showed me the latest he had from FUTABA.  They
    are coming out with a pretty much new line of radios, with very
    few exceptions.  All of the material shows that they are 1991 legal.
    The old models that are continuing are being updated and come with newly
    designed receivers.  
    
    He also told me that several flyers have sent their radios to FUTABA
    for upgrade to 1991 specs.  He said they were charged the normal
    $30-$40 for the upgrade.  The thing that amazed him was that FUTABA
    had given them NEW design receivers at no extra charge.
    
    Yes, it's true that independent results have not been published.
    I really don't think this is or will be an issue.  Indepedent testing
    may help them sell more radios, but at what cost?  It would surely
    be passed on in the price to us RC'ers.  I don't think we have to
    worry about FUTABA not being complient to 1991 standards.  To market
    anything less would be suicide for what is probably the largest
    manufacturer or RC radios.
    
    I suspect that we have'nt seen more than teaser ads from FUTABA
    because of the impact it would have on their distributors.  Your
    local hobby shop and mail order houses have large inventories of
    old spec radios.  These have to go before the dealers order more
    stock from FUTABA.  It comes down to economics and marketing.
    
    Gee,  I meant this to be 2 cents worth, but I appear to be short
    a nickel.

    I think that Chris is right that the delay is due to the manufacturers
    trying to unload old inventory.  That's why we couldn't get the
    new frequencies earlier in the season.  I've seen Futaba's new stuff
    and I'm sure that it soon will be listed in AMA as cmpliant.
    Airtronics just broke the barrier first.  I still will stay with
    Airtronics as my primary radio supplier due to my complete satisfaction
    with all of my present Airtronics radios.  They also have stayed
    with the same connectors on all of their servos.  Futaba has no
    valid reason to have different connectors for their AM and FM/PCM
    systems.  They even now make an adapter to go from one to another.
    Talk about creating an unnecessary inconvenience.
    

    Time for a couple of comments. As far as JR Century VII's go, I
    just bought my second one last week. I've never had a bit of trouble
    with the first one and I specifically wanted two identical radios.
    
    If I had the money, I'd have two JR Century VII PCM radios. Untill
    last week, I would have said the straight versions were just fine.
    Now I read in my club's news letter were one of the local paging
    services is causing an interesting problem in the St. Louis area.
    
    The paging service is on 72.240 which messes up channel 22. Everybody
    knows about that but what was just dicovered is that at some fields
    in the area you can't fly on channel 20 or 24 either. If your on
    20 or 24 you have no problems but everyone else gets shot down!
    The other interesting thing mentioned was the results from monitoring
    frequencies at on of the fields. With no one at the field the paging
    system on 22 showed up. Some guys went up on 52 and 40 and a weak
    28 springs up from 3IM. No problem since no one was on 28 at the
    time. Then someone turned on 34 and the channel 28 signal almost
    doubled. Neat stuff, you can get shot down without even knowing
    why.
    
    A final comment on 1991. As things stand right now, I'm not worried
    about saving my money up to buy a radio from Airtronics that the
    AMA has blessed (No slight intended towards Airtronics). I'm saving
    my money up to buy a big barn and some copper screen wire. I'll
    cover the inside of the barn with the screen wire and then ground
    it. Then I can fly my helicopter in the barn with no worries about
    radio systems. That's about the only system I can see working in
    1991!
    
    Dan Eaton (Who's not thrilled about 1991)
    

>    RC'ers in the St. Louis area behind my barn idea. See, the city
>    of St. Louis has a large covered amphitheater. It's been around

    You could just throw a wire mesh net over that big stainless steel
    arch you guys have, kind of like a tent, and then fly underneath
    it.  That way you'de have enough "Ceiling" to fly pattern events.

You should really wait and get an FM.  I think that the 1991
environment will be so dirty that AM will be useless.  From Dan's
note, it sounds like its going to be beyond my worst fears, at
least for those in metro areas.  As I've said before, because
we're "interdistal", we are exactly in the areas where the
sidebands from the adjacent pagers can leagally clobber us.  And
you better believe that they're going to modulate their signals
100% all the time!

We may be 20KHz from their center frequencies, but there is
nothing to stop them from modulating their sidebands right up to
our center frequencies.  That is their right, and they will do it
to get maximum coverage of their areas.

It doesn't sound like having 1991 radios is going to do us much
good, since once the pagers get going there will be myriad
combinations of them that can shoot us down.  In that
environment, AM will be a loaded gun.

    Re:last several
    
    Doug, I don't remember the formula for 3IM off the top of my head.
    I have a chart that list the deadly combinations by channel number.
    Maybe I ought to post that here. The point that makes the pager
    services so bad is you can't see them. If you show up at a field
    and see two guys are already up on frequencies that can add up to
    trouble for you, you don't fly. But what if you show up and there's
    only one other guy that can affect you AND a pager service you don't
    know or have forgotten about? Next thing you know your aircraft
    is screwing a hole in the ground.
    
    I like the idea about suspending the mesh from the Arch! After all,
    it is a symbol of expansion into the West. Aircraft provide a vital
    link in the transportation needs of the West. It all fits! Maybe
    I should contact the AMA and get them involved in this. They're
    suppose to be looking for a National flying site. Think of the 
    possibilities! Pylon racing around the legs of the Arch. Indoor/outdoor
    free flight with no worry about losing your ship. It just boggles
    the mind. And as far as the AMA goes it has the single most important
    item that goes along with any site selection. There are lots of
    fancy  hotels right across the street.
    
    
    Dan Eaton

    Just wading through the radio stuff and seeing the freq problems makes
    me wonder if someone markets a personal frequency monitor that would
    tell a modeller when it's safe (or more important, NOT safe) to fly. Is
    this capability too costly for an individual modeller? Do clubs have
    this capability? I'm out in the sticks and my biggest problem is
    cow pies. I'm worried about all that unseen "ether". I've seen the
    combinations of 72 mhz listed, are 27 mhz and 5x mhz still legal and
    prone to the same combinatorial problems?

    Maybe someone should make a personal monitor that is affordable.
    A receiver on your channel could be used to monitor for interference
    if some sort of output device were hooked to it that would tell
    if a signal was present.  THis could be used before flying to see
    if your channel is clear.  PCM may be the best bet in 1991.  The
    next step would be error correction coding. (Where's Fred Zayas
    when we need him)
    
    CHarlie
    

    Such a device already exists...
    
    Someone (RAM?) sells a device that you plug into your receiver.
    It sounds a tone when your receiver loses the Tx signal.  By 
    intentionally turning on Rx without the Tx on, the noise should
    sound.  If it doesn't, then your receiving on your frequency.
    
    In any case, none of it works if you are at 500ft and someone turns
    on and you get hit by 3IM.
    
    cheers,
    jeff
    

    Re: .49
    
    It does help in the case where you're all fired up and let loose and
    when the plane breaks ground it's that magic distance away where your
    transmitter isn't the primary signal. I fly alone a lot and end up
    holding my plane between my ankles while I fire it up on the flight
    line. I'm more worried about loud background signals than getting shot
    down by another flier. I guess transmitter impounds are a problem to
    some as are curious cows to others...
    

    RE:239.1245 and others here
    
    I've been thinking about the field plan where the pilots stand in
    a 10 foot square while flying. Maybe it's not so crazy. How do the
    RC car racers handle 3IM? In the very small exposure to racing I've
    seen, it seemed like everyone was standing together during the race.
    
    Dan Eaton

    
    FWIW,
    
    Went home at lunctime -- Latest Tower-talk is there.....
    
    Seems that Futaba has now introduced a fairly full line of 1991
    compatible (did not mention AMA certification) radios.  Including
    one discounted to $105 through Tower.
    
    Not sure on availability, but at least we now have some decent choices
    between Airtronics and Futaba for 1991 radios...
    
    Chris

    Re: < Note 105.54 by BPOV06::CAVANAUGH >

   >Not sure on availability, but at least we now have some decent choices

    I ordered one of the Futaba 1991 Radios from Tower last Saturday, when
    I received my Tower Talk, and there were 47 people on the waiting list
    already (I became 48), for various channels, for the new 5 Channel PCM
    1024 model.  The Customer rep I spoke to said that the next shipment
    was expected ~mid January, and they weren't sure exactly what models,
    channels, and quantities were expected. 

    Later,

    Don

>    a lot. The net of it all was to advise the current membership to
>    purchase 1991 std. equipment but to stay with the even numbers,
>    e.g. 42, 44, 46 etc. The thinking being that if there are any

Good idea but to my knowledge you won't be able to buy an odd channel
until after 1991.  Also remember - regardless of advertisements only
one vendor makes AMA CERTIFIED 1991 Radios - Airtronics.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

Had an interesting one over the weekend.  On Saturday myself and
another fellow were the only ones at the field -- very
unexpected, since it was a nice day. Anyway, I'd done some repair
work on my Eaglet and was taxiiing (sp?) up and down the runway
waiting for an instructor to show up and do a test hop for me.

I'm on channel 52 AM and the other pilot was on channel 18 FM.
To make a long story short, I clobbered him.  Drove his servos
over to full lock while I was out on the runway and he was in the
pits...about 60 feet.  I've never had this problem before, and
have had my radio certified silver by both the club and AMA
checks.

I took my radio in today to get it checked again, but I'll bet
it'll be ok -- I suspect that there's a pager or some other
service around that's giving me 3IM on 18, similar to what Dan
Eaton reported recently.

As has been said, this looks like the way things are gonna be.  I
talked it over with the club officers, and made an offer to keep
a log of all unexplained hits (that is, hits that cannot be
explained by a known turn-on in the pits).  Since neither the FCC
nor the operators are going to tell us about it, I think this is
our only defense; that is, a statistical accounting of incidents
to determine which channels are 'bad'.  I will be offering this
to the glider club, which I just joined, so I think that by this
summer I should have a handle on what's causing our problems.

All too often I've seen someone get hit, and everyone else talk
about it for a while, then the incident is forgotten -- we may
have been able to get away with it before, but not now.  I'll
also try to monitor the band, but I think this will be our main
tool. 

    John,
    there's another way you might be able to determine what's going
    on at your field. We recently acquired an environmentalist for
    our support group. Among the tools he can get his hands on to
    do environment checks is a spectrum analyzer. There should be
    an environmentalist there in the Springs somewhere. I could make
    some phone calls and see what the availability is if you'd like.
    Our guy is excited about actually getting to use the analylzer
    for something.

Ok. That is a resource that I hadn't thought of.  I bet the FCC
site up the hill from CXO1 has one of them environmentalist
types...When I get some specific data I'll look him up.

Actually, our club has access to a spectrum analyzer, which is
how I'm getting my tx checked.  I'll ask the guy who does the
checks if he can keep me posted on the pager operators in the
area. 

        Re:< Note 105.60 by CLOSUS::TAVARES "John -- Stay low, keep moving" >

                All  AMA  districts  will  be  given  frequency  scanners
        sometime early this year.  Nobody seems to know exactly what they
        will be capable of,  but the main purpose seems to be to set them
        up at flying sites and  have  them  scan  the  bands  for outside
        interference.  Once a club understands  the  interference sources
        it will be able to decide how to handle them.
        
        Anker

    Eric,
    It sounds like the frequency scanner is no different than a
    police band type scanner.  I purchased a Radio Shack Pro 2004
    this winter and do plan to do some testing on both 53 and 72 Mhz
    bands at our field.  I have tried it on 53 Mhz with my FM and PCM
    radios at home and it seems to be ok for telling me that there
    is a transmission on that frequency.  However, I can not measure
    magnitude or bandwidth, only tell of the presence of a signal. 
    However, for $419 (I heard you can get it for $359) It may be
    better than the added expense that you mentiones (>$500).

		________
	 /	  __|__  
	=========[_____\>
	/	__|___|__/  BREAK A BLADE,
			    Ken    	

    THis is a little late, but I have seen several incidents where AM
    clobbered FM at our field.  My solution is to not touch an FM set
    unless it is dual conversion.  The old FM receivers seem to be very
    intolerent of AM interference.  Several flyers at the CMRCM field
    have had their FM sets converted back to AM for this reason.
    
    CHarlie
    

Yes, the one that I clobbered on channel 18 while I was on 52 AM
was a single conversion Futaba.  This last month in Model
Aviation George Meyers talks about the 22-Channel Hit, which is
what I suspect happened in my case.

    I'm really surprised at the apparent problems with interference
    with the new Attack Futabas.  They are supposed to meet the 1991
    specs for narrow band.  If this is the case, they should be no problem.
    It sounds like this needs looking into in a hurry because all of
    our fields will be full of these systems due to their low price.
    I wonder if there is some form of interaction with other radios
    that causes problems with the transmitter.  If anyone has one of
    these, maybe we can test it on a spectrum analyzer with other
    transmitters present.  Better to understand it now than later in
    the season when lots of people will be flying.
    	It takes a major interference to knock out PCM and it sounds
    like both cases of interference that were reported were with PCM
    sets.  I'm willing to help with the testing and I have access to
    a spectrum analyzer here at work.  We could test at lunch time some
    day, hopefully before the weather is nice enough for lunch time
    flying.  Priorities, you know.
    
    Charlie
    

    When recently ordering a radio from Hobby Lobby, I found out
    something that the mags don't make all that clear. There are
    alot of radio's being advertised as "1991" radio's, when in
    fact only the transmitter meets those spec's. NOT THE RECEIVER.
    
    Airtronics radio's have BOTH transmitter and receiver meet
    1991 spec's which is a true 1991 radio system.
    
    Steve

    Dave,
    	Is it possible that we could make transmitter testing available
    at the meeting?  If so, I will bring my radios and offer any help
    needed to run tests.  If we need more notice, we could plan such
    a test for the April meeting and do it up right.  If there is equipment
    already in BXB2, it would make things easier, but I might be able
    to bring some equipment if needed.
    
    Charlie
    

Charlie - I would like to see the transmitter testing pushed out simply
because I can't make the next meeting (Phoenix).

I also have one of those Futaba Attack radios on ch 34.

Dave you are right the New Futaba receivers are advertised as 1991
BUT as I have stated before ONLY Airtronics has been certified.
I would have never paid $99 for my new Attack if I would have known
that I could have gotten the Airtronics for $119.  It just seems
like Futaba and JR are giving the finger to the AMA testing program
and it's a darn shame.

About testing - if we work some kind of deal with our district representative
we should be able to not only test for our own sanity but also get
some gold and silver stickers applied on all our old sets.  I think
we should take our time and try to do a dedicated evening of Tx testing.

BUT...  most of the problems recently state seem to center around
Rx problems which are much harder to test for.  Also Dan has Jack
Buckley lined up for the next meeting and you should not vary the
topic form scale cause this will be quite a good opportunity to listen
to the voice of experience.

If any one thinks they are exempt from this 1991 stuff read the latest
radio column in the AMA magazine - it's enough to make you loose sleep.

I think maybe we need less frequencies - not more.  If we only had
one channel then you would know when you could turn on.  We could build
cheap direction finders and sue any offenders who crashed our planes
cause they broke in an engine in their back yard - just over the
hill from a flying site.  Am I rambling yet?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Kay,
    	Don Kraft was asked at our CMRCM meeting last night about what
    it takes to be able to give out stickers and it sounds like a difficult
    thing to do.  We could look into it, but I think we would have trouble
    getting certified to give stickers.  I would opt for doing informal
    testing for our own peace of mind rather than to get stickers on
    our transmitters.  I don't want to get into legal battles over whether
    we know what we are doing.  (Even though testing transmitters is
    easy.)  I agree that we should plan this for the April meeting rather
    than rush into it for next week.  We should do a dry run before
    the meeting to set up the equipment so that we don't waste everyone's
    time.
    
    Charlie

Re: .69 and others

Remember that the current problems are PCM Rxs getting shot down by Futaba 
Attack Txs so the '91ness of the Futaba Rx isn't an issue (in this problem)

>    thing to do.  We could look into it, but I think we would have trouble
>    getting certified to give stickers.  I would opt for doing informal

But maybe we can coerce someone who already is qualified into coming for
the purpose of certifying Transmitters.

It would seem to me that this should be set up as a separate night since the
interest will end up wiping out the meeting (I would think)

    I'll bring my radio.  I want to see Eric's new toy.  I may want
    to persue one for the CMRCM club.
    

>    interference problem. Does anyone know if the tx AND rx are 1991
>    ready in the Attack series ?
>    
>    Mike

They claim to be - that's why I just got one.

Warning - if your conquest was AM and had the old Futaba AM servos
S28s or S33s instead of S128s or S133s then the new Attack series won't
be plug compatible with your old conquest.  All the new Futaba Radios
are now using what we used to call their FM plugs (J-series).

The charge plugs are still the same.

I have 5 radios now.  
1 Futaba FM Gold 7 channel 38, 
1 Cirrus FM 7 channel 38 (Futaba OEM version of above used from Dan Snow),
1 JR Century 7 Single Stick channel 38,
1 Futaba AM Gold 5 channel 34, 
1 Futaba AM Attack (1991) channel 34.

The Futaba Golds are not servo plug compatible with each other.
The Futaba AMs are not servo plug compatible with each other.
The Futaba FM is not signal compatible with the JR.
The Futaba Golds both have trainer cords but are not compatible with each other.
The Futaba AMs are not trainer cord compatible (the attach has no plug)
None if the radios have the dual rate switches in the same spot.

The Futaba FM is servo plug, trainer cord and signal compatible with the Cirrus.

All radios work fine.

If money was no object what would I buy - An Airtronics Vision - but they
are not generally available yet - but I like the idea of one VERY good
transmitter and several flight packs.  Marketeers have precluded that as
a purchase option since you can always buy a complete system for $99 but
the same receiver and servos and switch harness and battery will cost you $170.

If you think I'm a little upset over the present state of Radio marketing
your right..

Flame on

The AMA should not allow advertisers in there AMA magazine to say that
something is 1991 compatible unless they have been certified by the AMA.

As an aside the AMA should not allow advertisers in there AMA magazine
to sell gliders that clearly violate the AMA rule of the min radius
nose for safety.  If the AMA doesn't want to do that then they should
relax the min radius rule for gliders under a certain weight limit.

Flame off

Rambling enough?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Just got off the phone with Futaba, to my surprise I was told by
    the service department that my 5NLP conquest PCM receiver MEETS
    1991 specs. They said that I could send it in if I wanted and they
    would affix a gold sticker to it.
    
    So what I read from this is that even though Futaba does not advertise
    the Conquest PCM as 1991 compatable, it is in both the transmitter
    and receiver. I guess that they want you (and me cause I bought
    one) to buy the newer 5UAP 1024 PCM.
    
    Now I'm even more bothered that the AM ATTACK was able to hit me
    with interference.
    
    
    
    						Cheers, Dave
    

    
    I hope noone believes that the 1991 frequency system will be better
    than the system we have now.  Someone stated in this conference a while
    ago (John Tavares?) that when the new system is in effect all hell is
    going to break loose (or something to that effect).  I believe
    that is true.  I think AM will continue to shoot down FM (yes, even
    FM-PCM, even dual-conversion FM).  I think interference problems like
    3IM will be much worse, and I think we will see more and more planes
    being destroyed until local clubs enforce their own rules that prevent
    bad combinations from flying at the same time (once the smoke settles
    and we have figured out what the bad combinations are!!).
    
    For example, we know some bad combinations already; the Futaba Attack
    AM with certain FM sets.  I bet if you take the "incompatible" systems
    in question and test them with a spectrum analyzer they'll all check out
    fine, even to 1991 standards.  But there is absolutely no doubt in my
    mind that after 1991 we will find ourselves relearning all the stuff we
    learned over the past 10+ years or so - a good frequency control system
    is the only way to prevent hits and crashes, and after 1991 that system
    may have to be pretty sophisticated.
    
    Dual-conversion FM receivers help, PCM helps, narrow-band helps,
    and maybe someday there will be some design breakthroughs that allow
    any system at any channel with any modulation scheme to live with any
    other system at any other channel with any modulation scheme.  I'm not
    holding my breath!

    Bill

     
    I am currently looking for a new radio and was considering the Attack
    from Futaba. After reading this discussion I really don't know what
    to do. I certainly don't want to start shooting people out of the
    sky. At the same time if I buy an FM or PCM I 'm just as likely
    to be the one shot down. Sounds to me like we're in a real mess.
    Apparently the folks that are supposed to be watching over these
    things must be out to lunch !
    
    Mike
   
   

    
    I'm confused, are the situations described in the previous notes
    just as likely to happen with the "new" dual-conversion '91 FM
    receivers?  Am I kidding myself to think that I'll be immune from
    similar problems if operating a '91 spec FM radio?
    
    Concerned,
    
    Chris

    Re .86
    
    Yes it is a mess, however in reality the newer radios should have
    nothing to do with the current crop of problems unless somebody
    really blew it. We are still spaced at 40Khz only the cheap AM
    transmitters, and all 1991 receivers are more selective to
    SUPPOSSEDLY allow us to survive when odd channels are allowed
    in 1991.  So one would think that the newer radios would perhaps
    lessen interference problems.  I don't know what's happening,
    I do know that I got hit, and could repeat getting hit over and
    over with just me and another transmitter on (the Futaba ATTACK).
    
    I just looked at Bob Collins Futaba ATTACK on chan 16 on the spectrum
    analyzer. Looked fine to Bob and myself. It was not as clean of
    a signal as my Futaba 5UAP PCM, but still appeared to meet specs.
    
    Being new to a spectrum analyzer I may have missed something
    but we noticed that when we had his radio on (16) and mine on (22)
    there were second and third frequency peaks approximently 50-60
    Db below the primary signals.
    
    
    Oh well need to get somebody who understands how to properly run
    the analyzer...
    
    
    
    						Dave
    

I think that the AMA will outlaw AM within a very short time
after 1991.  They (the AMA Frequency Committee, George Meyers,
and Bob Underwood) have repeatedly stated that AM cannot survive
in the narrow bandwidth and crowded channel environment of 1991. 

With reference to the subject of AM hitting FM, this is the
"cure" that the AMA advocates: as time goes on, the AM sets will
prove unworkable and the owners will replace them with FM and
PCM within a few years of 1991.

To be more explicit with this, I think it was George Meyers who
stated that the AM radios would be phased out if for no other
reason than because so many of them will be destroyed in crashes!
And the other ones would be unused because the owner doesn't want
to risk a plane. That's the kind of responsible leadership we're
getting from the AMA. 

I wouldn't give you a nickel for a new AM radio right now (and
yes, my Futaba is AM, but its OLD). 

On the plus side, I think that the courtship and overtures going
on now between the AMA and EAA (Experimental Aircraft Assn) will
result in more clout for both of the organizations.  Clout is
what we're lacking right now.  It was the Fixed Base Operators
clout in the form of the pager and similar industries that got
them the band they have now.

Another plus: My crystal ball says that High Definition TV (I
think that's what its called) will force the abandonment of TV
channels 2 through 4, which occupy most of the frequencies
between the 50 mHz ham band and our RC band. This is because HDTV
requires a larger bandwidth than the current format.

I predict that these frequencies will be occupied by the Fixed
Base folks and will relieve the crowded conditions in our band.
Maybe even we'll be given our exclusive band back (despite what
the AMA says, we do NOT have clear channels...its just that we're
the only ones hungry or damn fool enough to occupy the guardbands
between the FBOs).   Perhaps this may even happen within our
lifetimes. 

BTW -- I don't remember if I said this, but I'm quite certain
that what happened when I hit the fellow on FM 18 with my AM 52
radio is a combination of the 22-channel interference that George
Meyers talked about this month, and his FM Rx being
single-conversion (he claims that his radio is "1991" but as
stated elsewhere, only the Tx is).   

    I can't see the need for additional channels. SORRY.
    
    
    I don't doubt that some field will rule to not allow the odd numbered
    channels. This would perpetuate todays enviornment. With app. 20
    present channels open right now what is the need for the other
    channels.
    
    Tom

    Wow, is this ever a hot subject!  Well I guess after just finishing my
    first plane and realizing the work that has gone into it, the prospect
    of it going down due to radio failure is quite alarming.  I, too
    have a 1991 Futaba PCM (mine's on channel 22) that I bought with the
    expectation that I would be as immune as possible to the trappings of
    any possible radio-related mishaps.  Naive or what?

    I was just wondering, what with the level of knowledge and expertise
    that we (actually you, I'm a rank amatuer) have in this conference,
    along with the various things said about the AMA in the previous few
    notes, if we shouldn't extract portions of them (the notes, not the
    AMA) and send them in to the those in charge at the AMA and the FCC.
    We can whine all we want, but it would be nice if our grumblings were
    heard by those who are in more of a position to help us than we are
    ourselves. 

    What say, go for it?

    Don

.91: Yes, I mean the 72 mHz radios.  You hams have your act
together, and my hat's off to you.  I could never master that dit
dah dit stuff, though I have held a commercial 2nd class license
which is supposed to be tougher than the ham license.  I also
note that most of the AMA folks who are so enthusastic about the
new frequencies are hams, and will never use them.

.92: Alas, my only qualification is that I read Model Aviation
very carefully, and that I have a high degree of interest in
this.

In fairness, (it occurred to me while I was at lunch) the AMA 
was never given a choice in this matter.  They were called to the
FCC and told here it is; like it or lump it, as the old
expression goes.  They made like marketeers in selling their plan
to the rest of us: if its a bug, make it a feature!

    As I understand it the FCC decided that they were going to make
    more frequencies available in the 72 Mhz band in our spectrum.
    So we (AMA) has a choice use them or loose them to somebody else.
    I would rather use them and suffer till this AM / FM stuff is
    settled out by Club or the AMA. If we do not use them, I understand
    that the FCC can decide to give them to somebody else. Not sure
    I'd want the odd channels being generated by a pager system or
    such that pumps out mucho watts, and uses ALL 20 KHZ of the band
    that's allocated to them. So were stuck with odd channels so
    why bicker about it. What we have to fix is this AM/FM interference
    problem. Why because it's here today and it WILL get worse. If
    the message gets out that we will no longer allow AM on 72 MHz at
    the various clubs, and people start returning their AM sets to
    the Hobby shops / Mail order houses that they bought them from,
    then you can be sure that the manufactures will respond.
    
    Unless somebody has proof that the AMA decided on the extra odd
    channels, not FCC, then much of this conversation is barking up
    the wrong tree. Before writing letters EVERYBODY MUST UNDERSTAND
    why things are going the way they seem to be. I don't know, but
    again I bet that the FCC put forth the new frequencies, and the
    AMA is sorta covering our A** by using the odd channels.
    
    Perhaps we should get a copy of the ACE RC videio that explains
    more about 1991. Or perhaps somebody who has seen and understands
    it can give us more info on the reason behind the new frequencies.
    
    
    
    						Dave
    
    PS: If enough club members start getting shot down by AM transmitters
        it won't be long before the club will say "NO MORE AM".
        (If that's how to solve the problem) 

    Before everyone panics, it seems to me that we should understand
    the problem better. (Attack vs FM PCM)  If the radio is clean on
    the spectrum analyzer even when the transmitter that was hit is
    also turned on, then something funny is happening to the PCM receiver.
    The thing to do is try to get the interference to happen while looking
    at the spectrum.  If there are no signals close in amplitude to
    the fundamentals of the two TX's, then something is getting around
    the filters in the receiver.  
    
    Nothing has changed this year vs last year frequency wise so there
    is no need to panic yet.  Most of the radios out at the field today
    are AM and have been.  The PCM sets are FM generally and they have
    been coexisting with AM for the past few years since PCM started.
    

    Fine, Let's draft a letter that represents DECRCM's position and
    send to to the right place(s).
    
    
    						Dave
    
    PS: Anybody want to draft this letter? I would but I do not understand
        the issues. How about you Eric? I'll sign it.....
    

I'll sign the letter also but...

Let's think about what the results of the letter(s) will be.

Nothing is going to change.  The new scheme will be implemented.
What can we do about it to make it livable to us.

1.  As Charley said - let's study the problem and find some technical
    empirical evidence that we can take action on.  I'm dying to see
    the spectrum analysis of channels 12,13,14 etc. when I turn on my
    channel 34 AM Futaba Attack

2.  Take action that is guaranteed to produce results such as:

    A.  Making a declaration that all DECRCM members will only purchase
        radios such and such on such and such frequency.  It could be that
        if we just limit our scope that we can avoid the problem.  It could
        be that Futaba is not playing by the rules - Airtronics claims that
        you can't meet 1991 with AM - Futaba claims they are.  I believe
        that JR and ACE do not make any AM 1991 equipment?  It is cheaper
        to change frequency than change modulation scheme.

    B.  In order to live with previously purchases equipment all we need
        to do is develop a frequency chart that insures compatibility.
        That is some frequencies exclude the use of other frequencies.
        So when you grab the channel 34 frequency pin maybe there is a
        cable attached to the channel 14 frequency pin to insure that
        no body can come up on channel 14 (hypothetical numbers).
        Maybe the frequency pin is for channels 14,34,56.  Who cares - 
        what is important is to not get shot down and not to shoot someone
        else down.  

    C.  For God's sake let's get some technical facts under our belt and
        some how form a consensus so that we can recommend what radio(s) and
        channel(s) to purchase to new folks in the hobby in various price 
        ranges.  As it stands now if a new flyer said "What radio - money
        is no object?" Can this ever happen?  And if we answered the new
        Futaba 9 channel 1024 PCM on channel 12.  Then a few (building) weeks 
        later I'll shoot him down with my $99 channel 34 AM Attack - why - 
        cause he purchased a frequency that has never been field tested
        against in the real world.

P.S.  As an aside here is a thought about cheap AM systems shooting down
      fancy PCM systems.  Maybe the PCM systems are two fancy.  After all
      essentially they check sum the transmission and insure it is 100
      percent correct or reject the signal.  Maybe this actually makes
      them fail where an FM or AM receiver might not have a problem.  Note
      this is not a fail save problem - it relates to the acceptance of
      the signal in the first place.  Even with fail save turned off a PCM
      radio will not respond to any transmission that does not have a valid
      digital frame present in the signal.  In memory terms I think the
      new PCMs fail on single bit errors where as FM and AM will integrate
      any noise along with the existing signal and appear to work.  Does
      this sound feasible?  Don't flame me for being electronically incorrect.
      I still have a 1st class FCC license tho it has been 20 years since 
      passed the test and have never used it commercially so I've forgotten 
      more about radio theory than I care to admit.

P.S.S.  Maybe Attack is an accurate name.  Remember the best defense is 
        a good offense.

P.S.S.S.  If you think about the old frequency boards solve all the problems.
          They have no slots for these new "BAD" frequencies so if you show
          up at the field on channel 12 - you can't fly cause there is no
          frequency pin for channel 12 - seems fair to me.

P.S.S.S.S.  Rambling now...

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

Just wanted to add that the spectrum analyser showed my Tx
conforming to the silver sticker, which it has, and with a little
spike down around channels 18-20.  I think the tech said it was
just above the noise, but perfectly legal.  (No, you're not going
nuts, I changed this last sentence from an earlier posting)
Interesting in that to get the sticker the AMA specifies
something like 55 db down in the sidebands (at is it 10kHz?) of
the main carrier.

They do not check the 22-channel emission, and it may be
something they should check.  I stood over the AMA feller's
shoulder at the Reno Fun-Fly when he checked my tx, (and Bob
Underwood was in the next booth) so I am positive that he only
checked the main carrier. 

Re: earlier comment about ACE:

Funny thing about Ace.  I swear by them; I think they're one of
the best outfits going -- but they are solidly AM with their tx
modules and with their 1991 receiver.  In fact, when the time
comes, I'll upgrade my Futaba by installing the Ace tx module.

The specs of their 1991 rx comes from double conversion and
crystal filter(s).  I have heard that they have FM in the works,
but so far have not announced anything.

We tried the system of designating each flying spot with a
specified set of frequencies to eliminate 3IM.  The system lasted
about 20 minutes!  You should'a heard the gripes.

Instead we reduced the spots to 5 and spaced them further apart.
For now that works, but really, I think the designated spot
system is the only way to go.  

Thanks for putting that in here Mark.  By coincidence or
whatever, one of the club members who works for Hewlett Packard
brought in a spectrum analyser run of the RC band.  What he did
was to set up the SA and let it sweep the band for 5 minutes
around noon.  This amazing little instrument will monitor a band
and put the spectrum of anything it finds on a laser-like output
graph.  Thus if a station like a pager came on for even a few
seconds it would be noted.  Back when I was tweaking one of those
things you were lucky to a sweep on the teeny screen! 

Here are the RC channels he found pagers or other emission on in
the Colorado Springs area: 

Channel    Source            Remark
16         Unknown
24         Pager             25 watts
26         Unknown           Low level
34         Pager             25 watts
44         Unknown           Low level
50         Unknown           Low level
54/56      Pager             25 watts
60         Pager             25 watts

He identified the pagers and their output power from a published
listing.  Also, most of these transmitters, and all the pagers
are on Cheyene Mountain -- THE Cheyene Mountain of NORAD fame.

I think that anyone who can buy, beg, borrow, or steal any amount
of time on one of these neat machines should do so.  Sorry, I
don't know the model number, but obviously, its made by HP.

In addition Steve read off a list of the trouble channels in the
Denver Metro Area: 12, 14, 16, 20, 22, 44, 52 (sob), 54, and 56.
When I fly Masters Scale (this year's meet is up there Al) next
year I won't be able to use my current radio.

    Well, I _did_ mention that I was on one of the 'suspected' bad channels
    in Denver, diddle I?
    
    But, seriously, I _still_ contend that the first/foremost/most
    effective protection against 3-IM is SEPARATION between flightlines,
    i.e. transmitters.  This past weekend, we had some ungodly number
    of flights put in by upwards of 200 scale ships without a single
    instance of [even suspected] 3-IM.  On the other hand, from what
    I gather from folks like Kay Fisher, Kevin Ladd,, Dan Miner, Dave
    Hughes, etc., you folks back there have a tendency/propensity for
    standing on top of one another, which action is an open invitation,
    no, it's just begging for 3-IM problems.  The first thing I'd do
    in defense against 3-IM, were I flying back there, is insist that
    a minimum 20' separation be strictly maintained betwixt flightlines/
    transmitters.
    
    Perhaps we've just been luck but, in 13-years/26 scale fly-ins,
    we've NEVER had a single instance of 3-IM or any other type of
    interference including frequency mis-management.  (Quick, where's
    some wood to knock on?)  I believe a biggest reason for this is the
    flightline separation we've always maintained.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

Sorry to hear you can't make it this year Al.  Sounds like you
need to take a break from the fast track.

The scale flyers up here are getting serious.  The fellow with
the B-17 will be flying a Twin Otter like the one the Academy (is
there any doubt which Academy I'm talking about?) jumpers use.
He's also got a 10-foot B-17 in the works.  Ivan is finishing his
F-102, and is working on a club project T-28.  There's also a
brand-new J-3 here based on one at a local airport.  And I know
of a few more scale birds from guys that may or may not compete. 

On Cheyene Mountain -- all the local TV stations, plus most FM
stations, plus the commercial users like pagers, and probably one
or two ham repeaters, not to mention NORAD are all up there in an
area of probably one or two square miles or less.  My test for
snow is to look at Pikes (no antennas) and Cheyene for the lights
-- if I can see them its not going to snow.  Anyway, you might
say that Cheyene is a regular Spectrum Rectum.  I thought of this
while shaving this morning and just had to work it in somehow. 

Got a problem for you wizards.  Lets suppose there's a 1-watt RC
transmitter with a plane, and an adjacent 25W pager, lets say, 15
miles away.  How far away from the RC transmitter can the plane
be before the pager signal and the RC signal are equal?  To
simplify things, the receiver cannot distinguish between the two
frequency-wise, its a straight shot from both transmitters, and
the tx power is the radiated power. 

I know that equal signal strength is not the criteria; that the
plane would probably go down long before it got that far out, but
just for the purpose of argument, lets use this as a measure.
Any takers?

    I just got the annual AMA mailing yesterday. You know, the 10 page
    newsprint paper and catalog they send out instead of the rule book. Had
    some nice, shiny gold stickers in it. 

    Anyway, buried in the fine print are some recommendations about radio
    safety. They have the right words, at least. 

    They recommend continual on-site monitoring with a monitor radio of some
    kind. This could be used as ammunition to ask clubs to buy their own
    monitors.

    They also must be listening to the Desert Rat, because they recommend
    a minimum 20' separation between flight stations.

    Any BOD members of CMRCM out there? How about pushing for the club
    to start complying with AMA recommendations?

    Dave

    re Note 105.115   about relative signal strengths 

        Besides the frequency differentials that you exclude from the
        problem, there are only a few other factors.  The received signal
        strengths are attenuated by distance and by antenna gain effects
        and complicated by the proximity to the ground of one transmitter,
        at least. 

        The spatial attenuation is easy to understand.  As the signal
        travels outward, the energy must be spread over an increasing area.
        In free space it would be the area of a sphere, increasing as the
        square of the distance.  Here the spreading is more like a growing
        hemisphere, but it still varies by the square of the distance. 

        Bouncing part of the signal off something like the ground can cause
        self-interference that can result in the signal varying in strength
        within a small space far away.  You probably want to ignore this.

        Having one antenna near the ground and the other up high can
        introduce other differences.  Ignore this also. 

        The antenna gain be more important; the power received depends upon
        the geometrical orientation of the receiving and transmitting
        antennas relative to each other.  Our RC antennas are short enough
        to avoid some of the TV antenna types of variations, but I would
        still expect the whip antennas to be much less effective when
        pointing at each other end-on instead of broadside.  And I notice
        that RC pilots, including myself, tend to point their whip sort of
        directly at the plane --- malappropriate behavior compounded at
        times by having the plane (and hence the plane's wire antenna)
        coming at the pilot. 

        To answer your question: assume that the pilot to plane distance is
        1/5th of a mile.  Then the distance ratio is 15/0.2 = 75, giving
        the pager a handicap [in power, not voltage] of 75*75 = 5625:1.
        This is divided by the pager source power advantage of 25:1 for a
        resulting 225:1 handicap --- about 23.5 dB in favor of the pilot.
        The pilot might squander some of this by pointing his whip at his
        plane; I suspect the pagers have vertical whips. 

        Ooops, I missed your actual question, "How far away from the RC
        transmitter can the plane be before the pager signal and the RC
        signal are equal?"    Three miles --- when the plane is 15 miles
        from the pager.    For me, three miles is out of sight, so the
        previous paragraph might be more useful; the receiver's specs might
        tell you how well it can reject a signal 23 dB down and hopefully
        offset in frequency. 

Thanks Al.  It does seem like problems are caused at less than
1/5 mile -- probably some of the factors you mention should be
included.  I did understand about the resolution factor, and
since that's something mentioned in tests it looks like a good
one to use for comparison.

On pointing the antenna.  I do it on purpose to give the radio
the weakest signal.  If the plane glitches, I move the antenna to
right angles.  This has saved my tail a couple of times.  

OK - I give up.

Last night I took out my brand new Futaba Attack (still in the box) and looked
it over thinking about sending it back and getting FM bacause of all the
rumors about Attack badness in this notes file.  While was looking at it I
decided to crank up the transmitter and see how well it talked to my
Futaba 5 ch Gold receiver in my Drifter II.  You guessed it.  They are 
incompatible.  The receiver hears the transmitter fine but the channels
are swapped around.  The throttle on the Attack runs the elevator on the
Gold receiver.

This morning I called Tower and got a return authorization number.
I'm sending the Futaba back and getting a cheap Airtronics FM.

I'll never purchase another piece of Futaba Marketing junk again.

Now anybody have some Airtronics radios that they would like to trade for
Futaba radios?  I'm serious - I have a 7 chan FM gold, 5 chan AM Gold and
one Cirrus 7 ch Gold that I would like to swap for Airtronics equivelants.

Also one JR single stick but I can't fault JR for compatibility.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Kay,
    	It is not uncommon to have channels swapped around between
    different models or brands of radios.  I have used futaba transmitters
    with airtronics receivers and had to swap the channels around to
    get things right.  There doesn't seem to be a standard for channel
    number vs function.  I had no problems flying this way with AM stuff.
    I'm not a Futaba fan either but I think you are being too quick
    to judge the new attack stuff as not good.  I have never seen a
    problem with Futaba's quality and I have only stuck with Airtronics
    for compatability with my chargers and servos and such.  I also
    like the less expensive spare parts.  You could rearrange the channels
    on your old receiver (just plug into the one that does the right
    thing) and it should work fine.
    
    Charlie
    

    Kay,
    Dan said it.  I started with an Airtronics system and from the old
    to the  new PCM, the connectors for servos, chargers, etc are the
    same.  Futaba is different from airtronics on Servo and charge
    connectors as well as from themselves.  This adds to the pain of
    cycling batteries as well as sharing servos and such between planes.
    I do have one Futaba radio that I bought without thinking.
    It has never given me any trouble but I still like my Airtronics
    rigs better.
    
    Charlie
    
    

    
    
    	I have been reading all these comments on what radios will meet
    1991 standards and I'm thinking about a new radio. But, I'm looking
    for a ground ( car, boat, .. ) system. I have not found a single
    ground system that meets 1991 standards.
    
    	Is this Air only ??  
    
    	Has anyone seen anything about a ground system that meets 1991
    	standards ?
    
    
    		Steve Peters
    

    I read the article that Eric mentioned last night.  It is much clearer
    about what some of these problems are.  I agree that the answer is
    Dual Conversion receivers (well designed), Independent Testing Labs
    to qualify stuff for 1991 and PCM.  In addition all of us will have to
    become more aware of potential problems and work to live with them.
    This may mean banning some frequencies at clubs where they appear to
    have problems.  It also means letting the old equipment go and buying
    1991 stuff when the time comes.  Many clubs are resisting this very
    foolishly, I think.  For safety's sake we should all be flying with the
    most reliable control systems available.  
    
    Charlie
    

I didn't mean to restart the religious war (well maybe I did ;^) but I'm faced 
with the problem of a limited budget and the RF crapshoot. I don't want to 
incrementally put several hundred dollars in the air to have some guy get told
to call his wife and shoot me down. I have a hard enough time "justifying" my
"toys" without saving $50 on a radio only to have it be insufficient (3IM-wise)
Radios are one of the largest all at once expenses that we face and the wrong
choice can be very costly. I guess I'll have to look hard at the $350 JR that
Evil Eric touts... Either that or sell several planes (ala Dan Snow) to generate 
the difference. I bought the Attack as a throw away due to the cost and wanting
get airborne with the least cost (in case it was another 6 years before I went 
back out) but the next one will be a financial commitment and I want to make the 
most informed choice I can (...justify to my wife).

I understand the Dual Conversion concept better (I was right just not sure) and
I like the idea of failsafe mode but what does PCM buy you on top of these 
features and what else should be considered? I've looked at additional flight
packs vs total systems and don't want to have to "upgrade" to a better Rx at the
"whole system" price. Do I really have to buy top of the line in order to feel
safe? What about these "problems" with the Futaba 1024 systems. I hate the idea
of buying something that hasn't been proven in the (pun alert) field for a 
reasonable amount of time. Do I just merrily go on with my AM Attack until I
get shot down real hard?

A few weeks ago I got hit (radio interference) with a dirt bike that was acting
(I assUme) as a spark Tx. Will any of these systems/features tolerate this type
of hit better (besides just throwing up its hands and going to failsafe mode)? 

  I can't remember if anyone has said much about the new 
Kyosho Series 91 Advance radios, so I'll start something here.

  The 5-channel PCM lists for $199.99 and the ad states "The 5-channel
includes an FM PCM receiver with dual conversion."
        .
        .
        .
 "The 5-channel PCM transmitter includes a variable hold/fail-safe feature.  
Should your signal be interrupted in flight, the variable hold will maintain 
the last servo position until the interference subsides.  If the interruption 
is longer than 0.8 seconds, the fail-safe takes over.  The receiver responds
to pre-set functions commands, giving you the time to escape from danger."


  The 7-channel FM lists for $209.99 and the ad states 'The 7-channel's
receiver is 1991 narrow band, with crystal filtering and dual conversion."

  Also "Both offer excellent narrow band characteristics."

--------------------------------------------------------------- 


  Does anyone have any 'first/second/third hand' information about these
radios?  Or does anyone have any gut feels for them?


  As I told Dan Snow the other night....The price sounds good, but I don't
want to be the first one to find out they are a piece of junk with my new
L4!


		Jim

P.S.  Roy, (president??) of the 495th club had his new, 1991 Futaba xxxxx 
radio tested at one of the club meetings a couple of months ago....it 
failed to meet the 1991 specs.  He sent it back to Futaba and after 2 
months they returned it to him with a gold sticker on it saying it was fine.
At Tuesdays meeting he had the guys re-test it for him, and the comment from
the back of the room after testing was 'Do you want me to put the silver 
sticker OVER the gold one, or next to it?".  A two year old Futaba Conquest
tested better (< 1db over gold standards) than his new 1991 radio!

>  <<< Note 105.152 by AKOV11::CAVANAGH "R/C planes..The bigger the better!" >>>
>                            -< Any word on Kyosho? >-
...
>  The 5-channel PCM lists for $199.99 and the ad states "The 5-channel
>includes an FM PCM receiver with dual conversion."

Airtronics Vanguard 4 ch PCM = $189.96, 6 ch PCM = $239.96

This means that Kyosho pricing is directly comparable with Airtronics.
But...
No Kyosho Tx or Rx has made the AMA 1991 list and Airtronics has a good
reputation so why buy Kyosho unless it offers some unique feature that the
others don't.

> "The 5-channel PCM transmitter includes a variable hold/fail-safe feature.  
>Should your signal be interrupted in flight, the variable hold will maintain 
>the last servo position until the interference subsides.  If the interruption 
>is longer than 0.8 seconds, the fail-safe takes over.  The receiver responds
>to pre-set functions commands, giving you the time to escape from danger."

To my knowledge every PCM radio system that supports programmable failsafe 
settings (the only one that doesn't that I know if is my Vision) does this.

>  Does anyone have any 'first/second/third hand' information about these
>radios?  Or does anyone have any gut feels for them?

My gut feel is that the Tx and Rx are probably well made and my major concern
would be availability of parts in the long run.  We know we can get support
for Futaba and Airtronics and JR.  They all have tons of good servos and 
connectors and switch harnesses and trainer cords and...

Last winter in Phoenix I wanted a Futaba trainer cord.  So I went to the
nearest hobby shop and got one.  Try that with Kyosho!

>P.S.  Roy, (president??) of the 495th club had his new, 1991 Futaba xxxxx 
>radio tested at one of the club meetings a couple of months ago....it 
>failed to meet the 1991 specs.  He sent it back to Futaba and after 2 
>months they returned it to him with a gold sticker on it saying it was fine.
>At Tuesdays meeting he had the guys re-test it for him, and the comment from
>the back of the room after testing was 'Do you want me to put the silver 
>sticker OVER the gold one, or next to it?".  A two year old Futaba Conquest
>tested better (< 1db over gold standards) than his new 1991 radio!

I've been putting my money where my mouth is lately.  In the last 6 months
I have spent over $900 on Radios and ALL the money has been on only
stuff that has made it to the AMA 1991 certification list.  I really
like Futaba stuff but I won't even buy a servo from them until they
start getting on the list that they promised Al Casey they would.
If you crash and your Tx and Rx aren't on the AMA list you are negligent.

I'm not saying you shouldn't buy a Futaba radio.  I'm saying you shouldn't
buy a Futaba radio today.  Wait until they prove compliance.  If you can't
wait then buy a JR or Airtronics from the AMA list.  Remember not all the JR
and Airtronics radios are 1991 safe.  Only radios on the list that also
have Dual Conversion receivers.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    If someone was inclined to buy the Kyosho PCM, I would give AMA
    a call. If I remember correctly, the last add I saw for that radio
    advertised that they had the AMA gold sticker. They may have the
    certification but just didn't get it in time to make the last model
    aviation publication.
    
    Steve

As we discussed while sprinting through CXO1, the wires are
reversed -- you have a smoked servo because of this, I have a
smoked servo because of this -- how much more proof do you want?
At least I can say that when I plugged the servo in, I knew
damn well that the wires were reversed, because I re-reversed
them myself to fit the Dean's connectors I use.  I was
thinking some wonderful far-out daydreaming thoughts at the time.

The December 1989 issue of Model Builder contains a review of
the Polks system by Stu Richmond, admittedly not a great radio
expert.  However, Stu mentions that the new Aristo servos are
very much improved, and are plug-compatible with JR and Futaba.
This implies that JR and Futaba are also compatible.  This does
remove my objection to the Aristo radio, though I also found out
that it has 9 tx batteries, which is another bummer in my book.

One thing that has endeared Airtronics to me, aside from the high
quality of their servos, was that I though I could dependably
connect a Deans to the Airtronics connector.  This is why I
re-reversed the Airtronics connector as described above.  I found
out after I did this that it is not dependable and is not very
good for the connector either.  Now I maintain both Deans and
Airtronics connectors and am using the Airtronics servos through
a cut down patch cord made from an aileron extension.

My only gut feel for the Kyosho is that its probably the same
quality as Futaba.  I don't like it because Tower is pushing it,
and I don't like products that are pushed.  Government policy.

No, it was a 9-cell nicad pack, the article said so.  This was
with the PCM transmitter, and is quite common with PCM, tho I
think the Airtronics has 8.  

I'm only thinking that if I had to replace the pack it would be
one more cell to buy and to deal with.  Actually my home-brew
constant current charger will handle up to 15 cells, maybe more.

On the weather, you can forget Coleraddy.  We've had a cold front
come thru here and drop a smidge of snow.  Though it was a 'warm'
25 or so here last nite.  Sounds like the desert spoiled you; you
need a therapy trip out there when its 110+ in the shade.

>    As to radios, I've given up with Bob.  I'd like ta' hope this
>    experience would convince him to move up to modern technology but I

OK Al - time to recall some old note you wrote about Futaba.

You had some friend there who promised you that they (Futaba) were
in the process of getting independently certified and ultimately be
placed on the AMA published list.  Months have went by and we have
been anxiously waiting for Futaba.

I am running shorter in rope every day (I just purchased 3 more
new Futaba servos the other day) before I have to make a commitment
to my next power plane radio.  Futaba marketing already lost my sailplane
radio business to Airtronics and I am not hesitant at all to order
20 Airtronics servo pigtails and start soldering all my Futaba
servos BUT...

If Futaba was on the list I would be looking at (saving up for)
their PCM-9.  But (especially after hearing about the local
AMA testing rejecting brand new Futaba transmitters) I will not
purchase any new radio from any vendor that does not make the AMA list.

The WRAM show is coming up here on 24-Feb and some of us might drop
some big bucks on new "1991" equipment.

I love Futaba equipment.  I've never had any problems with it.
I think they have the leading edge in human engineering and
features right now.

But  -  their adds keep point out "1991" and yet they haven't been
independently certified and Tower has started toning down the "1991"
fluff from Futaba stuff (eliminated it completely from the Attack series).

Soooooooooo

Back to the rambling topic - could you please talk to your friend again
and update us on Futaba's future.  Every month when the Model Aviation
arrives I flip right to the back and check the list and say "DAMN".

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

>    Futaba radio, but the only 1991-ready FM model available in my price
>    range, (I think it is the 5UAP) requires a HAM radio license to
>    operate!!?  What gives?  Will this become a new "rule" in the future?
>    
>    I asked if any of the Airtronics radios had this requirement, and the
>    answer was no.  Sooooo...I ended up buying an Airtronics 6 channel FM
>    1991-ready unit for 159.95, significantly less than I was going to
>    shell out for the Futaba.
>    
>    Any comments?

Here's a cheap shot.  I doubt if this is what the Tower operator had
in mind but...

There are NO 1991 AMA Futaba radios.  So Tower told you the correct thing.
If you get a HAM band then there is no 1991 requirement - so Futaba
(who can't pass the spectrum analyzer tests at of "Better than
-55 db @ + or - 20 KHz @ 3 KHz RBW) is OK on the Ham bands.

Want more controversy read last months (not this months which arrived
two days ago) column in model builder by Eloy Marez.  In summary he says 
that only HP makes a spectrum analyzer that has a 3 KHz RBW position and 
some vendors (read Futaba) only test on other spectrum analyzers what test 
at 5 KHz RBW.

Eloy's advice is buy the one that can pass anything (read Airtronics, JR).

If your local AMA authorized testing station does not run an HP spectrum
analyzer he just selects 5 KHz RBW and slaps a gold sticker on it.
Did he do you a favor?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

re 1173.9

>Here's a cheap shot.  I doubt if this is what the Tower operator had
>in mind but...
>
>There are NO 1991 AMA Futaba radios.  So Tower told you the correct thing.
>If you get a HAM band then there is no 1991 requirement - so Futaba
>(who can't pass the spectrum analyzer tests at of "Better than
>-55 db @ + or - 20 KHz @ 3 KHz RBW) is OK on the Ham bands.


I don't think so, Kay, for two reasons: 

1. You're not quite correct about ham bands and 1991. There are new
   frequencies in the 50 MHz ham band that ARE 1991-style channels.
   In fact, they are numbered channels, 0 through 9. You need narrow
   band equipment for these new frequencies, because the channels are
   closely spaced. The old 53MHz channels are also still valid, and 
   you can use old wide band equipment on them.

2. I can't believe you would imagine a Tower operator having a sophisticated
   enough understanding of these issues to pull a stunt like that! In
   fact, I seriously doubt that Tower Hobbies or its telephone operators
   are interested in the "legal" AMA sanction of radio equipment. If
   Futaba or an other vendor tells Tower that their equipment is "1991",
   then that's what Tower will say. They don't care, it's the vendors'
   responsibility, not theirs.

   But I do agree with one thing you said: It was indeed a cheap shot!

   The old, old saying still holds: "Let the buyer beware."

Dave

    Specs are wonderful things. Especially to people that do not know how
    to interpret them. Let alone the people who set them. They are not a
    heck of a lot more than arbitrary numbers. I would imagine that perhaps
    Futaba cannot meet the spec. Perhaps they are only a mere 50db down at
    +/- 20Kh. It's like many audio specs one vendor states there THD (total
    harmonic distotion) at .0001%, while another only makes it to .001%.
    The average person just is'nt going to care as they will not perceive a
    difference! 

>    The average person just is'nt going to care as they will not perceive a
>    difference! 

In 1991 the average person may have his radio tested at a competition
and not be allowed to compete.  Then he will perceive a difference.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    As a newcomer to this whole issue, the last few notes have my head
    spinning.  Did I screw up with the Airtronics (I don't think so) or did
    I get "taken" by the order taker??  I do have an engineering
    background, but I must admit, when you walk into a conversation at this
    level, it takes a while to get oriented around the real issues and to
    be able to sepatate the wheat from the chaff.  I think what I heard is
    that Futaba may be spreading around some FUD in order not to loose
    business because they have a hole in their product line.
    
    If I should reconsider my Airtronics purchase, let me know.
    
    It's getting a little warm in here, but I love it!
    
    Regards,
    Joe

	Joe, in answer to your two questions; No and No.

	You did NOT screw up in purchasing the Airtronics. All else aside
	they are EXCELLENT radios and meet or exceed all 1991 specs of both
	the FCC and the AMA. Lets let the others debate the validity of either
	set of specs. Whether the requirements are valid or not Airtronics 
	meets or exceeds them.

	You did not get "taken" by the order taker. In my humble opinion
	they did you a favor. I think the VG4R FM is a great low cost set
	(much lower than Futaba) and it includes the trainer system thats
	only available on higher priced Futaba sets. You also get a true 1991
	dual conversion receiver thats been in use for a year or two now! It
	is not brand new. All this applies to the VG6DR, plus you get 2 more
	channels. I own 2 VG4Rs and a brandy new VG6DR. I like them all. 
	Oh yeah, USE THE TRAINER SYSTEM! You'll love it, and it saves planes.

	I don't know what, if there is one, Futaba line is comperable to the
	Vanguards in a features/price comparison, and I probably won't ever
	find out. I think Airtronics is currently the only reasonably priced
	1991 radio available right now and they've definitely got my business 
	for the forseeable future. If I want a really fancy set and inherit a
	fortune I might move up to JR, but I really don't see Futaba in my
	furture for a long time to come.

	I suspect your evaluation of what Futaba is doing is probably close
	if not right on the money. They need to sell a large number of old
	sets, and they're going to do damn near anything they can to get rid
	of those before they condescend to conform to the specs. Who knows.
	
	Forget the controversy, build and fly the plane and enjoy the hobby.
	You've got a reasonable starting package (I'd have suggested an
	Aerostar, but thats another religous argument) and should be in the 
	air in no time. Once you start flying all this will undoubtedly 
	be forgotten.

	Randy

    It may be warm Joe, but don't sweat it! The Airtronics will serve
    you perfectly well for your intended purpose, and I don't think
    there is a noter out there who would (or could) dispute this
    statement with objective evidence.
    
    Terry

This has been a good introduction to the topic of "Opinions", which
is by far the most favorite topic in this notes file. I place a
stated value on my own opinions:  My advice is free, and if I'm
wrong I'll give you your money back. 

For most people their radio brand is like their car brand - If you're
a Ford man you'd never own a Chevy, and vice versa. From what I can
tell from reading this notes file, both Futaba and Airtronics are
reputable manufacturers and their equipment works well. So, you
did not make a mistake taking the Airtronics.

The AMA has set up a formal procedure for "certifying" radio equipment.
They list "certified" radios in their magazine each month. So far,
Airtronics has had their radios certified, Futaba has not. This may
or may not have anything to do with how the radios perform. 

It has been rumored (in this notes file) that some manufacturers have
bribed their way onto the list, and that Futaba isn't there because
their radios don't meet the specs. These are pure rumor. We all like
to make those kinds of statements occasionally, and you should be
careful to weigh any claims against their source (or lack thereof).
Everybody in this conference is entitled to state their opinion, and
it's up to each of us to decide who to believe. This provides a
richness of discussion that I for one enjoy. Admittedly, it can be
confusing to a newcomer. But it's a good lesson to learn: There are
lots of "experts" in this hobby, many of whom will not agree with each
other on all points, but most of whom have valuable experiences and
opinions from which we can learn.

Now, back to the topic at hand. We are in a difficult situation. The
current technology of our world requires users of the radio spectrum
to use it efficiently. Radio frequencies, like real estate, isn't being
made any more. The need for it is increasing, so we have to be more efficient
in our use of it. The RC hobby has been acknowledged by the FCC as a
bona-fide user community for the radio waves. This is due in large part
to the efforts of the AMA, to whom we should all be grateful, whether or
not we think they got us the best deal.

I know this is getting long winded - bear with me...

The radio frequencies (channels) that have been assigned to RC are 
interspersed with other services such as paging services. These services
may be located as close as 10 kHz to our channels. This requires us to
do two things:

1. Our transmitters must put out a narrow bandwidth of signal, so as not
   to interfere with these other services. This is very easy to do, and
   very easy to measure.

2. Our receivers must be finely tuned to "hear" our transmitters, but not
   the other nearby signals from the other services. This is hard to do,
   and harder to measure. This is the source of all the controversy.

A lot more can be said about what should be done about it, but that's subject
to differences of opinion. One needed solution is that local clubs need to be
much more active in their monitoring of the radio waves. We were assigned
lots of channels in order to allow us to avoid those that have interfering
services nearby. This is easy to say, but in practice it requires constant
monitoring and communication among club members. The other way is the hard
way - wait until a few people get shot down by a new paging service until
we decide to figure out what's happened. Kind of like waiting until 10
people are killed at an intersection before putting up a trafic light.

I know this is more than you asked for. If it served to give you the feeling
that this is a pretty complicated issue, that's good - it is. But don't
be scared off by it. The best bet is to find a club, and find some people
in the club who seem to know what their talking about and take their advice.
Avoid the ones who are dogmatic in their positions without being able to
explain why.

This is a fun hobby, and you don't have to be a radio whiz to use a radio.
But just like it helps to know the fundamentals of flight and aerodynamics
if you want to fly, it now is becoming necessary for you to know some of 
the fundamentals of how your radio works.

Dave

    Joe,
    
    You've broached a good subject, and I see that it has 
    generated some very good responses.  I'm a JR man myself,
    but add my vote of confidence to those who say that you 
    did the right thing, a lot of my friends swear by their
    "Airtronic's".
    
    Keep us all posted on your progress with the Eagle II.
    
    john
    

    Joe,                             
    
    Dave's reply brings up lots of good points.  As he says, brand
    preference when it comes to radios is _very_ much like loyalty to one
    or another make of car.  I happen to be a Chevy and a Futaba man...
    for the same reason in both instances:  Both have given me exemplary
    service with an absolute minimum of fuss and/or bother.
    
    Discussion as to the merits of Chevvies belongs in another conference
    but my preference for Futaba results from an 8+ year relationship with
    several models of Futaba radios and, this is the honest truth, "I'VE
    YET TO MISS THE FIRST SIGNAL, LET ALONE CRASH OR DAMAGE AN AIRPLANE DUE
    TO RADIO!"  Therefore, until or unless someone can give me a REAL good
    reason to change, I'll fly Futaba forever; the only thing that could
    ghange that stand is if I suddenly started having chronic problems that
    other makes weren't experiencing.
    
    As to the AMA's 1991 specs, Futaba is not the only mfgr. that still
    offers for sale non-1991 equipment.  I think it's foolish for anyone to
    buy a radio that'll be obsolete in a year but I can't fault Futaba or
    any other mfgr. for wanting to get rid of these systems while they can.   
    As Dave says, it's another case of Caveat-Emptor and the newcomer is
    well advised to do some research, ask some questions _before_ he rushes
    out to buy something he may not be able to use, sell, trade or even
    give away in a short time.  He probably does the same when considering
    the purchase of a car, a house, a machine tool, golf clubs, etc. so why 
    not apply the same logic to our recreation?
    
    I, personally, don't think it's possible to buy a bad 1991 radio from
    Futaba, JR or Airtronics nowadays...they're all good and FAR superior
    to what we had just a few years back.  Certain regions have certain
    radio preferences and I _always_ advise a newcomer to buy what is
    popular in his area, not to mention familiar to and trusted by his
    potential instructor(s).  Out here, the clear preference is for Futaba
    while, back there, it sounds like Airtronics is the runaway favorite.
    
    Either way, unless you'd bought _any_ mfgr.'s soon to be obsolete,
    single conversion, AM model, you couldn't have gotten a bad radio
    system.  Since the preference in your area appears to be Airtronics, I
    suggest you stay with what you bought but understand that a Futaba
    would've served you just as well.
    
      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    In a way, I'm really glad I stirred up all this discussion as it's been
    invaluable for me.  I respect all of the opinions expressed so far, and
    a special "thanks" to Dave who did a super job in .16 explaining and
    sorting out the basic issues.
    
    Whoever said there is a richness in the diversity of this notes file is
    right on.  I have a feeling that this is the ONLY environment that can
    lead to a solid understanding of what I'm doing, and I for one
    appreciate all that's been said.
    
    I'll feel OK putting this issue to rest very soon as I expect the
    shipment from Tower any day now.  Like I said...can't wait to get
    started building, and when I do, I'll be like a kid again having a ball
    and probably totally unaware of the worlda d around me.  Ain't hobbies
    wonderful ways to preserve our sanity?
    
    Thanks again for a terrific discussion.
    
    Bye for now,
    Joe

OK Al - here's a hypothetical situation.

Suppose you and most of your friends qualify for masters
at regional qualifiers and in the process your radios
are checked for AMA Gold compliance with Tectronics spectrum
analyzers.

Now months later you show up at the Masters and low and behold
they are testing transmitters with a HP spectrum analyzer.

Now suppose (just suppose) they fail 90% of the Futaba transmitters.

What will happen - well the CD will over rule the requirement and
the contest will go on but...

This is only 1990 - so we know from almost bitter experience that either
the AMA had better change the guideline for testing from 3 RBW to 5 RBW
OR everybody with Futaba transmitters should modify or change their
transmitters.

If the AMA changes the guideline that is surely not fair to the vendors
who did follow the published guidelines.

If they tow the line and start taking gold stickers off new transmitters
half there membership will consider forming their own parent organization
(maybe the AM(B)).

Remember this is a hypothetical situation!

What should the AMA due?

What should Futaba due?

Like you I have had great luck with Futaba and if I had to guess
that one of my radios wouldn't work this evening - I would guess
the Airtronics or JR would randomly fail before my trusted true Gold Futaba FM.

Kay who would really like to buy a Futaba PCM-9 at the WRAM show the 24th
    but doesn't dare.

P.S.  Moderators - after this note calms down it should be moved to the 
      1991 note.

    Kay, 
    
    I can't honestly offer even a speculative answer to yer' hypothetical
    situation as I, quite frankly, don't understand enough about the
    operation of our radios to understand the hypothetical question.
    
    I hope you don't think I'm being purposely evasive as, I assure you,
    I'm not.  Hell, I don't know 3 RBW or 5 RBW from a pancake, let alone
    understand the difference between them or the implications of one
    spectrum analyzer versus another.   
    
    Should such a situation ever take place, I expect the Masters would
    make whatever intelligent decision best suited the contest at no
    compromise of safety.  And if that meant I couldn't fly, so be it.
    However, I don't forsee that situation occurring before Futaba finally
    clarifies its position and takes whatever action is required to rectify
    the conflict.  I simply can't believe, being the industry leaser it is,
    that Futaba would leave all its customers holding the bag and, thus,
    severely compromise its market position, possibly to the ruination of
    the company.  I feel confident there'll be some workable solution to
    the controversy (_whatever_ it is) before too long.  Let's face it, it
    HAS to happen or Futaba'd have to close its doors and I doubt anyone
    could seriously believe they'd let that happen.

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

Dave's reply a while back soft-petalled a point that is being
missed here: there is no problem with ANY transmitter
manufactured today meeting *FCC* guidelines for 1991.  Virtually
anything manufactured in the last 5 years will do it, since the
FCC guidelines are those required for a silver sticker.  This is
no problem and these transmitters are all legal by FCC
regulations.

The point of contention is in RECEIVER guidelines set by *AMA*. 
As has been pointed out in other notes, the FCC could care diddly
about the receiver.  Its the AMA that has set guidelines for 1991
receivers and these guidelines are absolutely not enforced by
law.

Receiver parameters are difficult to enforce because they require
detailed laboratory equipment and analysis to test.  The
receivers that have been submitted to this testing are those
receiving the AMA approval by being listed in Model Aviation.
These receivers to date are all currently made by Airtronics, all
by JR, and the bootleg receiver sold by Sheldons.  No others
qualify for the AMA approval, but all others do legally qualify
for operation in the 1991 environment.

1991 is legally enforced in the transmitter, but in practice is
implemented in the receiver.

Sorry for the lecture tone, I thought we'd settled all this
before.

re: 1173.22 by CTD024::TAVARES 

>Dave's reply a while back soft-petalled a point that is being
>missed here: there is no problem with ANY transmitter
>manufactured today meeting *FCC* guidelines for 1991.  Virtually
>anything manufactured in the last 5 years will do it, since the
>FCC guidelines are those required for a silver sticker.  This is
>no problem and these transmitters are all legal by FCC
>regulations.

My dissertation a few replies back was intended to be a general
technical background of the situation. You're right about the
transmitter not really being the problem today - I said it too. The
FCC is concerned about our transmitters interfering with other
services, period. They are not concerned about other services
interfering with us. We're considered to be "secondary" users. Same as
portable telephones (read the fine print on your portable telephone
and it says the same thing). That may not sound fair, but we have to
live with it. We RC'ers, of course, think otherwise because if my
portable telephone gets some interference I won't lose hundreds of
bucks worth of equipment, or risk somebody's life. That's why we
want and need to go beyond what's technically "legal" if we're going
to really have our needs met.

>The point of contention is in RECEIVER guidelines set by *AMA*. 
>As has been pointed out in other notes, the FCC could care diddly
>about the receiver.  Its the AMA that has set guidelines for 1991
>receivers and these guidelines are absolutely not enforced by
>law.
>
>Receiver parameters are difficult to enforce because they require
>detailed laboratory equipment and analysis to test.  The
>receivers that have been submitted to this testing are those
>receiving the AMA approval by being listed in Model Aviation.
>These receivers to date are all currently made by Airtronics, all
>by JR, and the bootleg receiver sold by Sheldons.  No others
>qualify for the AMA approval, but all others do legally qualify
>for operation in the 1991 environment.

While true, this has been the point at which some people mistakenly
decide that they don't have to worry about the receiver specs, because
the vast majority of AMA members will never fly at an AMA event, and
as long as their radio is "legal" that should be ok, right? Not so.
The oft missed point is that the AMA guidelines for RECEIVERS are
intended to PROTECT US. The FCC doesn't care if you get shot down, the
AMA does. It's a safety issue, not to mention the dollar cost of lost
equipment. Do we need enforcement by law before we decide to protect
our financial and time investments in our models? People using poorly
designed receivers may get shot down with no explanation or evidence
of why it happened. This is due to local conditions, which is part of
the problem. Folks who fly out in the middle of a midwest cornfield or
southwest desert may be less likely to have problems than those flying
near metropolitan areas. The AMA is trying to make guidelines to
protect us all.

A very close analogy is that of the car radio. If you have a cheap car
radio, it works pretty good until you get to a place (such as Eastern
Mass., NYC area, southern Cal., etc.) where the radio stations are
saturated, in which case you may get nothing but interference (and
even occasionally  in rural areas your cheap radio will get
interference, and you may or may not be willing to put up with it).
You need a better designed radio to make sense out of the garbage. The
difference is, you can HEAR you car radio, and thus you know when
you're getting interference. Since you can't HEAR your airplane's
radio, you can only guess what it's actually receiving.

>1991 is legally enforced in the transmitter, but in practice is
>implemented in the receiver.

Exactly the point. The manufacturers in their ads, since they want to
sell equipment, emphasize the "easy" part, which is "legal" compliance
with 1991 (actually it's not 1991, it's NOW), which their transmitters
can easily meet. Even most old AM transmitters could be tuned up to
meet at least silver sticker. What the manufacturers, the AMA, and
all of us have to contend with is the hard part - the receiver. And
if we as a community don't agree that we care about our investments
enough to go beyond what's "legally enforced", then we're going to have
a lot of busted airplanes out there, and I sure hope people don't get
hurt.

Dave
(p.s. It's fun to debate when we're all in agreement!)

    What about AMA insurance if you use a radio that is not on their
    legal list? I'm just about finished my first plane and this note
    is making me nuts.
    Walt

    re .24
    
    Me too ! AMA's 1991 legal radio list and AMA insurance coverage
    have no connection. I hope. Given the manic state of litigation
    in this country, this does give rise to several interesting
    conjectures. In the event of a marginal, sticky , insurability
    question, I wonder if AMA lawyers could fall back on this
    point to deny payoff ? Any comments ?
    
    Terry
    

RE: last two from Walt and Terry.  If you're going nuts, you're
beginning to understand 1991.  This is potentially a legal
monster that I think we'll all be going nuts over in the coming
years.  But for different reasons than you suppose.

First of all, to set your mind at ease, please understand that
the AMA guidelines have absolutely no legal bearing.  As Dave
just said, these are the recommendations that AMA has made to
manufacturers to ensure safe operation in the 1991 environment. 
They have no power to enforce them, and any move that AMA has
attempted to make to require them for, say participation in
sanctioned contests, has met with *very cold reception* from the
membership body (can you guess why? :-) ).

No, all the AMA can do is say that this is what they'd like to
see and hand out their certification for those that do -- kind of
a ribbon for valor under fire or something like that.  Actually,
according to the latest reports from George Meyers and Jim
Oddino in their respective columns, receivers meeting the
guidelines far exceed the actual requirements for 1991 operation
that are being experienced in the field -- in other words, these
receivers are bulletproof.  

For the legal implications of 1991, at least as far as I see
them, please refer to my notes in the 1991 topic.  In summary
though, it will be impossible for an RC'er, and by implication
the AMA who will represent him in court, to prove that he was
legally operating on a clear channel, and that therefore, he was
not the one who was negligent in causing his plane to go out of
control.  And you were wondering why no insurance company will
take us!  This is the part of 1991 that the AMA is not talking
about.

    Hey you guys!!! Don't you know that the FIRST 1991 ready receiver was
    made by ACE R/C from Higginsville MO in the USA!! This is really a
    first class double conversion receiver. I have 2 of them which I used
    to replace the very poor receivers in my old Tower system. The Tower
    transmitter just made it thru the 1991 test. They also have systems
    which start in the $175 range with Gold transmitters and the new
    receiver which are very good starters. The parts for this equipment is  
    available in a day or so after a call to ACE and they have service
    centers around the country.  I have the ACE OLYMPIC V system and use it
    in my INDY CUB. An excellent basic radio.
    
    i
    

re: 1173.26
>that are being experienced in the field -- in other words, these
>receivers are bulletproof.  

Please - "bulletproof" is far too strong a word. Remember that the
1991 guidelines are intended to take us many years into the future.
There are few if any commercial transmitters in the "in-between"
channels, AT THE MOMENT. You can count on that changing.

Again, I don't want to scare anybody, but I do want to warn against
being lulled into complacency. If a 1000 watt commercial transmitter
turns on 10 kHz away from your airplane's channel with your .25 watt
transmitter, no receiver that you or I can afford is going to be
unaffected. And of course no receiver is immune to a second transmitter
on the same channel. Even the best "failsafe" modes still result
in an uncontrolled airplane.

re: 1173.27

>    FWIW, when this dies down I'll relocate the pieces as best I can. 

IMHO: PLEASE don't break this into pieces - I'm sure that's not what you
intended to  do, but the flow of dialog in notes like this adds much
context and meaning to the content. Rename the base note, or move the
contiguous replies to a more appropriate note. If you really want to
extract the "good stuff" then you'll need to do a technical edit of
the whole series of replies and recreate the context and flow. If you
have time to do that, then go to it!

Dave

    Re: .-2,
    
    Interestingly enough, I don't believe Ace (like Futaba) has been AMA
    certified either, even though their receiver was, indeed, one of the
    first, if not _the_ first to be 1991'd.  BTW, Cliff Weirick of
    Airtronics will be visiting my shop tomorrow night and I intend to pick
    his brain and, company rivalry aside, see if he can explain this
    resistance to AMA certification thing to me.  Of course, I'll report 
    whatever findings I come up with here.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    Ask him when airtronics is going to make info avail on the new 10
    channel fully synth....(mumble) radio with the ergonomics case and the
    touch screen panel for programming

Dave: I would like to add this footnote to my "bulletproof"
comment; I hope I dont sound too defensive...I'm a little
sensitive to that accusation lately!

I used the word because George Meyers commented a few months back
that the approved receivers, I think he was specifically
referring to Airtronics, have been used in a full 1991
environment in the field with adjacent Public Service stations
and have operated with nary a glitch.  This of course, is no
substitute for moving to what the AMA refers to as a "clear
channel" (said reference is what I call The Big Lie). It does
point out however, that with careful design operation after 1991
will be practical.

While here, I might as well add a little to my note concerning
legalities of 1991 operation.  All the following remarks are
gleaned from comments in Model Aviation by Meyers, Marks, and
Underwood.

In fact, the AMA has absolutely no power to enforce 1991 beyond
requiring the silver sticker transmitter.  Suppose old George
Grump has this nice Kraft silver sticker  Old Wide Band AM
(OWBAM) transmitter and  receiver.  He's been flying it for years
and nobody is gonna tell him to buy a new one.

So he goes and crashes into a Little Old Lady who sues him for
everything he's got, which of course, the AMA being the insurance
carrier, must defend.  They cannot get out of this, even though
George broke the club and AMA rules...the law says that the
silver sticker is all that's required, and that's the end of it.
AMA must pay.  Now, they can discontinue the club's status as an
AMA club for not forcing George to change, but that's all the
recourse they'll have, and that's after they lose the suit.  This
is also true if George is not a club member but is an AMA member,
or if George is not flying at the club field.

I picked the OWBAM example because that's the far extreme of
equipment that will be out in the field after 1991; the same
example goes for all equipment, AM, FM, PCM, wide band, narrow
band, and all combinations thereof; the AMA must pay.

Enforcement of this rule is going to be a real problem; as I
stated elsewhere, in the end its up to us clubbies at our field
boxes to do it.  George Meyers has especially stressed the point
lately that its up to us, in the form of buying equipment from
manufacturers that support the AMA guidelines to get the message
across that we want safe equipment.  He's not doing this because
he wants to support the AMA party line; its a matter of life and
death for our sport.  For everyone's sake, I pray that we're mean
and nasty to those that break the rules.

First I would like say that I agree with nearly everything said
recently.

However I was talking about Transmitters in reference to the
5 RBW and 3 RBW AMA guidelines.

I know it is harder to test receivers but the reality is the
495th authorized AMA gold sticker tester has failed brand new
Futaba Transmitters (ref some other note).

>         <<< Note 1173.32 by CLOSUS::TAVARES "Stay Low, Keep Moving" >>>
...
>In fact, the AMA has absolutely no power to enforce 1991 beyond
>requiring the silver sticker transmitter.  Suppose old George
...

I think they do.  (1) They can test your transmitter and refuse
to let you attend AMA sanctioned events.  (2) They can refuse to 
admit you into the AMA.  (3) They can add the gold sticker
requirement to meeting their AMA safety rules - for which they
claim you are not insured unless you comply with them (questionable
but that is another note).
...
>Enforcement of this rule is going to be a real problem; as I
>stated elsewhere, in the end its up to us clubbies at our field

We should be able to say "Gold sticker to no fly!".

Now as regards the receiver - if that is what your talking
about then I have to agree - it will be tuff for the AMA or anybody
to check them and insure safety - but as I see it as more and more
high powered beepers take to the air waves the skies will be cleared
of old wide band receivers.

P.S.  I just called Futaba and asked about 1991 compliance.
      They took the party line.  Everything they have that is being
      advertised as 1991 meets or exceeds all AMA guidelines.  They
      claim that all the paperwork has been submitted to the AMA and
      it is just a matter of time till it is published.  Great.
      I just called the AMA.  HQ referred me across the street to
      the magazine.  The magazine referred me back across the street
      to HQ - but they said the next issue had the same list of 
      certified radios as the March issue - No Futaba.  So I called
      HQ again and was referred to Bob Underwood (who was out but
      would be available Monday).  Bob is suppose to be the one
      that would know if Futaba has submitted their paperwork.
      I hope to have time to call them Monday.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    This has been UNBELIEVEABLE!!!!!
    
    I thought I was asking a simple question, and it turns into a 33 reply
    marathon.  Or should that be Talkathon?  
    
    I have to confess that I never thought there was this much controversy
    over radios when I decided to get started in this hobby.  But the
    dialog of the past 33 notes has made me painfully aware of the REAL
    issues I will be faced with as I join the ranks of RCer's, and I for
    one have gained a healthy respect for safety and for knowing what your
    doing before jumping in.  As a newcomer, I certainly can't add anything
    to this interaction, but rest assured, I will be much more conscious
    about treating the whole subject with a great deal of care.  All of us
    who are new to all this owe the veterans a debt of gratitude for
    showing us all sides of this critical issue.
    
    Thanks for the education...I know it will come in handy.
    
    BTW: Jus t started building the Eagle 2 yesterday.  Got the tail
    feathers done.  It's goin' great and I'm having a ball.

    
    In the UK, a similar thing happened when they introduced 35Mhz for
    flying models.
    
    They would only allow certified equipment at competitions. I don't know
    of any equipment that failed, although one AM outfit fell out of
    fashion from heresay evidence.
    
    The insurance was (and is) still provided for any "allowed" models with
    any radio, even on the crowded 27Mhz band, but then we don't have so
    much private litigation. The insurance covers you for 3rd party injury
    and damage to the tune of (approx) $1.5M.
    
    Mark

The plot thickens...

In the March 1990 issue of RCM (the one we all got two of) in the Radio Spectrum
Column by Jim Oddino a letter to him flames him for recommending Futaba
radios and brings up several points what we have been talking about but in
addition it says

"It appears that you did not hear about the Futaba 1024 interference problems
in pattern at the 1989 Nats (especially on 6 meters),..."

In Jim's answer he says

"...and yes I did hear about the problems at the Nats.  However, it seems that
it is a perfect example which makes my point, that you ought to go to the 
field and see what works.  One could read Model Aviation and see that Futaba
1024s took the top five places in FAI at the Nats, and 12 out of the 17 top
places at the World Championships.  You could look at the Futaba ad in the same
magazine and conclude the 1024 is a 1991 system.  However, if you bought one on
the low six meter band and then tried to fly it at the Nats' site day in and
day out (and the conditions would be the same as Nats week), you would be one
unhappy fellow.  However, if you had gone to the high end of the 72 MHz band
and bought one of these, you would be perfectly happy.  Seems logical to me."

OK guys - these are quotes out of context - but I have a simple question.
Anybody know what happened at the Pattern Nats?  Obviously we will never
find out by reading event coverage in magazines that accept Futaba 
advertisement.

P.S.  I tried to call Bob Underwood of the AMA today and he is taking
      the day off.  His secretary is digging thru his paperwork to find
      any Futaba certification info and call me back (doesn't sound too
      official).

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

Bob Underwood of the AMA called be this morning.
He was still in Washington State for a trade show and talked my ear off.
Futaba still has not sent him the paperwork to get their name on the
AMA certified list.  He said that they promised at Thanksgiving that
it would be "Shortly".  In January at the IMS show he again talked
to a Futaba representative in the Futaba booth and the rep told him
that they were having difficulty with the testing lab getting the work done
and that he (Bob Underwood) should expect the paperwork at the end
of January.

He suggested I call Futaba's Steve Helms - their marketing manager.

(It all boils down to marketing doesn't it!)

I also asked about the 3 KHz RBW stuff and he said that the AMA
sent paperwork to the FCC to relax their specification to 1 KHz RBW (between
300 Hz RBW and 3 KHz RBW) in order to accommodate all the vendors
and the fact that some testers do not have a 3 KHz RBW position for test.

Anyway the AMA will make no notice about this until after they get this
blessed by the FCC.  As it presently stands the sticker stations are suppose
to test to the 3 KHz RBW for gold stickers - with no exceptions. 

I asked about the rumors that sticker stations (our 495th) failing
new Futaba units and he said he had heard that some of the cheaper
units were occasionally failing but to his knowledge not many and not
any of the top of the line units.  He was going to call the guy from
the 495th and check with him to keep current.

Bob admitted to not being a high tech Radio expert but seemed to be right
on top of things to me.

I also asked about the problem with the Pattern competition at the Nats.
Bob said he wasn't there but got in on the problem after it started cropping
up.  It turns out that there were some antennas in the mountains running
Low Frequency Navy stuff to communicate with Subs.  Additionally there
was some other RF source (I forgot what he said).  The result was there
was a "High Noise Floor" and the 6 meter PCM units were going into failsafe.
He said Futaba's Steve Helms was looking into it.

I asked Futaba only?  He said he wasn't sure and wouldn't want to say
without having actually been there.

I asked PCM only?  Again he wasn't sure.

Reading behind the lines what I'm hearing is - It probably was Futaba
only but that may easily be that the only new PCM 6 meter radios were Futaba.

Well - he promised that he would be at the WRAM show and so did Futaba.

Now back to Futaba.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

>He suggested I call Futaba's Steve Helms - their marketing manager.
...
>Now back to Futaba.

I called Steve Helms the afternoon of the 5th.
His secretary answered and he was in a meeting all day.
She said that Bob Underwood had called earlier and left
a message for Steve and said I would call.

I left my number and expected a call later that day or the
next (yesterday) - no call.

I was reading a March-1989 (11 month old) article from Flying
Models by Bob Adiele(sp) reviewing the Futaba 9VAP PCM radio.
In this article Bob says that Steve Helms had told him that
Futaba had just completed independent certification of this
radio for the AMA guidelines and would appear in the AMA list
shortly.

Now I have a real problem.  What can I possibly ask this
guy on the phone given that I have reason to NOT believe 
anything he says?

I'm booked in the same motel as the AMA guys for the WRAM
show.  Sure would be nice to share a Jacuzzi with the AMA
and Futaba.  I hope Steve Helms is a little guy cause I
would like to say some things that I just wouldn't dare
if he was much bigger than me!  Maybe Dave Hughes could
set by me?  What do you say to the head of marketing when
your only complaint with the company is their marketing?
If I get a chance later today (after California wakes up),
I may try calling again.  Sure starting to look like I'm 
going to have to get another Airtronics Vision instead
of Futaba.

I'm starting to read something between the lines in all this.
Why hasn't Futaba certified their systems that they advertise
as AMA certifiable?

1.  They are lying in their claims that they will certify.
    A definite possibility.

2.  They are having problems with certification.
    A definite possibility.  I would guess that now that
    they have listed 16 Tx and 6 Rx as 1991 that some of
    the lower end systems can't make the spec.  So they
    either have to loose face and only certify some percent
    or they have to change design and meet the spec or
    they have to wait for the spec to be relaxed.

3.  Both of the above.  A definite possibility.

4.  They are just having a schedule slip in their certification
    process and are telling the true to the best of their
    knowledge.  If you believe that you deserved to own
    an AM Attack on channel 20.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

>To my knowledge, please point out a sample ad, Futaba only
>advertises their systems as being "1991 Ready", not "AMA
>certifiable".  This is true, since in order to be "1991 Ready"
>they only have to meet the silver sticker, and they easily meet
>the gold.  This is the transmitter spec that is sanctioned by law
>FCC.
>
>As I've said before, AMA certification is completely different in
>that it is NOT a law, only a recommendation, and the critical
>component is not the transmitter, but the receiver.  And this is
>the spec that will determine practical application of the 1991
>environment.  Airtronics, for instance, is both "1991 Ready" and
>"AMA Certified".

OK - the two page add in the Jan-1990 Model Aviation says at the
bottom of the page "Watch for future AMA RC equipment certification
listings."

Not exactly false advertising - but given that they have been saying
this for over a year and given that they have told Bob Underwood several
times that it is due shortly - to me it is false advertising.

In addition they ship all their "1991" transmitters with gold stickers
on them.  The authorized testing station criteria is to test for
transmitter band width at 3K Hz RBW.

Futaba's Glen Toma just called me on the phone.  
He said the technical assistant that told me the other day
that they had submitted their paperwork to the AMA was miss informed.

He said that they will be sending a letter of intent to the AMA at the
end of March.  I said "Letter of intent" - intent to do what.
He said "to be on the certified list".  It was confusing but my
interpretation was this would be the necessary paperwork to be
in the magazine list.

Anyway - I asked about the review that was over a year ago where
they said they had completed testing on the 9VAP.  He said that was
true and the problem was there was a disagreement on the 3 KHz RBW
and the FCC's specification of 300 Hz RBW and that thru a conference call
with other vendors and the AMA they had agreed to change it to 1 KHz RBW.

I said "But if you already passed the 9VAP a year ago it must have
passed at 3 KHz RBW - won't your transmitters pass at 3 KHz RBW?"
He said they do.  So I said then why don't you just meet the 3 KHz RBW
spec and get on the list.  He said that there were political reasons
why and he couldn't talk about that.

This conference call description corresponds with what Bob Underwood told me.
But Bob said that this proposal was being sent to the FCC and until
the AMA heard from the FCC the requirement for gold sticker stations
was still testing at 3 KHz RBW.

I told Glen this.  Then I asked when they ship new Futaba radios
and put gold stickers on them if they test at 3 KHz RBW or at 1 KHz RBW.
He said 1.

I said bye.

Given that most testers don't have a 3 KHz RBW setting and given that
during the conference call most vendors agreed that it would be OK
to relax the spec to 1 KHz RBW - I would conclude that transmitter
band width wise the Futaba transmitters are safe to use.

I would also conclude that a gold sticker on a Futaba Transmitter
is worth less than a gold sticker on other vendors radios and is
worth less than a gold sticker put on any transmitter by the
authorized testing guy in the 495th club.

Now back to Bob Underwood of the AMA.

News flash...

=======================================================================

Just before I finished editing this file Glen Toma called me back again
he said he made a mistake and they DO test to 3 KHz RBW on all their
transmitters before putting on gold stickers.

While he was on the line I asked about the Pattern problems
at the NATs and he said Steve Helms and others went up
to investigate and spend 3 days flying there.  Steve flys 50 MHz
and at the end of the third day they did pick up some VOICE interference
at one of the 3 pattern sites on 50 MHz but they were not able to
isolate it.

I asked if the problem was only on PCM radios.
He said yes to the best of his knowledge  - but cautioned that the problem 
was only at the Pattern site for the FAI and expert and nearly all
if not all the radios were PCM.

I asked if the problem was Futaba only.
He said yes to the best of his knowledge  - but cautioned that the problem 
was only on 50 MHz and nearly all if not all the radios were Futaba.

I pointed him to John Hill who has been testing and failing new Futaba
transmitters for the 495th squadron.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

So...it is a transmitter problem that they have - I remember
reading about this, but thought it was a nit with AMA
certification, not with FCC certification.  Thanks for the clear
explaination, could you explain RBW?

Did you ask about the receiver testing which will be needed for
AMA certification?

>So...it is a transmitter problem that they have - I remember
>reading about this, but thought it was a nit with AMA
>certification, not with FCC certification.  Thanks for the clear
>explaination, could you explain RBW?

Sorry - I really can't other than to say that the issue before last
in Model Builder in the "Electronics Corner" column by Eloy Marez
he goes into it in detail.

Bottom line is testing to better than -55db @ + or - 20 KHz * 3 KHz RBW.

Testing at 300 Hz RBW (the FCC spec) would be easier to pass
and testing at 1 KHz RBW is in between.

>Did you ask about the receiver testing which will be needed for
>AMA certification?

Not directly in the last few phone calls but I have heard of no
receiver problems.  But then how would we unless every club around
Boston kept a channel 20 radio just to test other receivers with?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

More gossup from the UUCP net.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

Article         2095
From: [email protected] (UNIX Network News)
Newsgroups: rec.models.rc
Subject: Re: 1991 stickering
Date: 12 Feb 90 22:05:59 GMT
Organization: John Fluke Mfg. Co., Inc., Everett, WA
 
>transmitter for sure, but I don't remember seeing any sort of sticker on
>the rcvr.  The gold sticker doesn't say "AMA certified" or 1991
>certified as I recall. I'll check and post if it does have one.
From: [email protected] (Robert Huggins)
Path: fluke!roberth
 
There would be a Gold sticker that would read RCMA AMA RF CHECK on the bottom.
 
> I understand that Futaba has some sort of
>quabble going on with the AMA about certification, but I'm not
>sure what the details are.  I've heard something about the way
>AMA measures bandwidth is the issue (BTW, if anyone has the full
>scoop, I'd be interested in hearing about it). 
 
This is not the first time I have heard this.  The AMA method uses 3KHz
resolution bandwidth and I think Futaba wants 1KHz.  I did an interesting
test with my Attack 4, at 3 KHz resolution bandwidth the "skirts" were 
-54.3 dBc, at 1Khz bandwidth they were -58 dBc.  Actually the narrower
the resolution bandwidth, the more accurate the reading however, if the
other guys are in spec at 3 KHz bandwidth, they will be that much better
at 1 KHz bandwidth.  I think this whole thing with Futaba is a political 
one and they are trying to beat the spec rather than having to recall a 
bunch of units.  
 
>
>To add to the confusion, I've read that the Jan 1, 1991 date is just
>a manufacturers cut-off date and not an absoulute drop-dead date
>for the use of older systems. Is that true and if so it seems to
>me it's going to be a LONG time before older systems fade away!
>
I would be interested if your 7UAF has a gold sticker with the above 
writting on it or if they just slap on any gold sticker?  I would also 
be interested in hearing your comments on the 7UAF being that I am seriously
considering purchasing one in the next few months.

Well, I did my thing for 1991 this morning, and ordered the
Airtronics MD7P from Tower.  I was going to wait until the Tax
Man Commeth, but the radio was still at $264 and I expect it to
go to $279 by the end of April, then to $289 by year's end.

I've been very keen on the Vanguard 6 PCM, but decided against it
because the MD7P has more features for just a little more money,
and I was impressed by George Meyer's recent testing that showed
the Airtronics FM receiver to be solid even in the worst of 1991
conditions.

So, Coleraddy flyers look out -- the Old Pin Hog is moving to
Channel 42!

P.S.  Al, I followed on your advice and threw in an OS .40 FP
too, just in case the Ace Fox Jockey bombs out.  Ain't nothing
more miserable than a cranky engine, go ahead and ask me if its
true.

    Well, what does everyone think of the new replacement receivers that
    are being sold by RMC (?)??  
    
    They have been added to the certified list by the AMA mag and sell for
    $80.00.  They are available in both AM and FM models, for Futaba and
    Airtronics.... Of course this price makes it tough to decide to take
    a chance or just by a new radio!
    
    I think the most surprising thing is that they are selling an AM model.
    I had kind of come to the conclusion from this topic that AM was not
    going to be a good alternative in 1991....
    
    Also, what are the implications of having this receiver being used
    without it being matched to the radio??
    
    Comments?
    jeff
    

    My opinion is that $80 is too much to pay for a bare receiver.  Far
    better to spend $120 for a complete 1991 system with new nicads,
    servos, and even a free TX.  Until aftermarket receivers get reasonable
    (<$50) I won't get excited about having one programable Tx and several
    planes, each with it's own flight pack.
    
    Charlie
    

Hobby Dynamics has a two page spread in the May issue of RCM touting JR's new
X347 radio. I notice one of the features they high light is 'affordable' flight
packs. I wonder if this notes a change in their price structure on flight packs?
More likely they think if they tell us its cheap enought times we'll believe 
them. I need another radio and the X347 would superbly meet my needs for another
helicopter radio plus a radio to play with fixed winged ships with. However, 
like Charlie said in 105.201, I'd probably get more for my money by buying a 
Century VII and a cheap fixed wing radio.
times 

>            <<< Note 105.200 by WRASSE::FRIEDRICHS "Go Bruins!!" >>>
>                               -< 3rd party rx >-
>
>    Well, what does everyone think of the new replacement receivers that
>    are being sold by RMC (?)??  

Don't know anybody that has purchased one yet but I haven't heard anything
bad about them - even in the UUCP network which doesn't censor their
negative comments on vendors as we in Digital have chosen to do.
    
>    They have been added to the certified list by the AMA mag and sell for
>    $80.00.  They are available in both AM and FM models, for Futaba and
>    Airtronics.... Of course this price makes it tough to decide to take
>    a chance or just by a new radio!

I noticed an add the other day for $70 and prior to that they had consistently
been advertising for $60 and are $60 in my latest Sheldon's flyer.

Since I have JR, Futaba and Airtronics to me the choice is easier.

	RCD 7 Channel FM Dual Conversion   = $60 (Sheldon's prices)
    Airtronics 6 ch FM Dual Conversion = $65 (Sheldon's prices = I got two)
    Airtronics 8 ch FM Dual Conversion = $90 (Tower prices)
    Futaba 8 ch FM Dual Conversion     = $140 (Tower prices)
    Does Futaba make a 6 channel FM Dual Conversion?
    JR Prices ???

Sooooo - when I need receivers for my Vision I purchase Airtronics because
they only cost $5.00 more then RCD and I can go back to a major vendor
if I have any problem.

When I need receivers for my Futaba 9VAP I intend to go to RCD since
they offer everything I need at 1/2 the Futaba cost.

I only have one JR and don't presently plan to get any new receivers - but
if I did I would purchase RCD - this assumes that the JR prices are as high
as I would guess (over $100).  This also assumes that I would call up JR
and confirm that their Airtronics compatible radio would work with a JR 
transmitter and I would ask if I could get Futaba connectors cause they
can be forced to fit on JR.

Now about servos.  For my money Futaba gives you the most servo quality
for your dollar and I don't mind cutting off the ends and putting on
connectors for Airtronics or JR or Deans.  This is however a very limited
view as I have only had one type of JR servo and a few of the low end
Airtronics and Futaba Servos.

>    I think the most surprising thing is that they are selling an AM model.
>    I had kind of come to the conclusion from this topic that AM was not
>    going to be a good alternative in 1991....

That could be a whole note by itself.
    
>    Also, what are the implications of having this receiver being used
>    without it being matched to the radio??

I don't believe this is a problem any more.  With the gold stickers on
the transmitters you are guaranteed that the transmitter center frequency
is very tight and receivers can be tuned at the factory.  I have
4 receivers flying off my Vision transmitter and 3 receivers flying off
my Futaba 9VAP - no problems so far - and everything I have read leads
me to believe this is the norm now.  Be warned however that I do not
crystal swap - not now - not ever!

                <<< WEWAND::$69$DUA0:[NOTES$LIBRARY]RC.NOTE;1 >>>
                  -< Welcome To The Radio Control Conference >-
================================================================================
Note 105.201                      1991, ANYONE?                       201 of 202
LEDS::WATT                                            8 lines   5-APR-1990 09:35
                               -< Too Expensive >-
--------------------------------------------------------------------------------
>    My opinion is that $80 is too much to pay for a bare receiver.  Far
>    better to spend $120 for a complete 1991 system with new nicads,
>    servos, and even a free TX.  Until aftermarket receivers get reasonable
>    (<$50) I won't get excited about having one programable Tx and several
>    planes, each with it's own flight pack.
>    
>    Charlie

$80 - $50 - how about $59.96

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################
    

    As someone else has pointed out, page 121 of the June 1990 issue
    of Model Aviation lists Futaba radios that are now AMA listed. 
    All are FM or PCM; none AM.

    In the June 1990 issue of RC Reports, page 32, there is an upgrade
    (narrow banding) offer by Futaba for their older radios starting
    in October (when a lot of pilots would be sending in their radios
    for annual maintenance anyway).  This offer will probably appear 
    in all of the other magazines as well, so I won't extract it here.
    The prices look very reasonable, even the upgrades that involve
    equipment swaps.

    Hmmm.  I am at the point where I can finally invest in my first
    plane/radio combination.  I am currently involved in Cars and Boats,
    so I am not unfamiliar with RC in general.  However, this 1991 hoopla
    has me somewhat confused.  The Car and Boat crowd doesn't appear
    to be to concerned with this, in fact I have not heard word-one
    in the pits---a reflection on the 'crowd'?  Beats me.
    
    Anyway... I know I need a 4-channel, and I'd like to stay with Futaba.
    I beleive I'll go with s133 micro-servos; all that leaves is
    the raido---the reason for this note.
    
    Question:
    
    Can I buy a 4-channel Futaba Attack and *not* have to worry about
    1991?
    
    Also...
    
    Could someone, in brief form---if possible, provide a 'Dr. Suess'
    version of what 1991 means to a fledgling-flogger?
    
    Thanks in advance, and I just love this notesfile---Great info here!
    
    Fred

    Fred,
    
    As to what radio to buy, please refer to the listing of AMA approved
    radios near the beginning of the AMA news section of each month's Model
    Aviation magazine.  As I recall, the Futaba Attack series is not
    approved for 1991 operation but the Conquest series is.  Double check
    by referring to the listing in MA.
    
    1991, as simply put as I can think, means ALL aircraft radios,
    Transmitters AND receivers must be certified to operate in narrow band
    to prevent interferring with each other and/or being interferred with by
    the numerous pagers that share our frequency band.  Surface frequencies
    are also affected but, owing to the fact that boats and cars don't
    fall out of the sky, creating serious safety/liability considerations,
    the subject may not be considered as crucial by boaters and car
    operators.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    Thanks for quick reply, Al,
    
    Well, that explains the lack of intrest.
    
    I take it that a 4-channel Attack (assuming it *not* approved)
    absolutely can not be used after jan-1-1991?  Lest the guys in the
    dark suits, wearing foster grants, swarm out of the trees and rappel
    from Slicks into my field to confiscate my radio and sweep me out
    of existance? :-) 
    
    Fred

I thought it was mentioned last week (in here) that the Attack WAS on the latest 
list and that for $10 you could get your Tx converted to narrow band and there 
was a rumored $40 trade up on the Rx??

Jim (current Attack owner/moaner ;^)

    Re: last-2,
    
    Please don't takee whatever I said as gospel.  I'm not sure, without
    consulting the listing in M.A., just what is approved and what is not.
    That's why I recommended you also check the certification listings in
    Model Aviation.  I just _thougt_ I remembered someone's comments in
    here fairly recently saying the Attack was not certified but the
    conquest was...perhaps I got it backward.  In any event, please check
    M.A.
    
    As to flying an uncertified radio after 1991, no one's gonna' come up
    and arrest you but flying such a radio constitutes a clear and present
    safety hazard and, should an incident occur, you and/or the club could
    be in for some real liability hassles.  MUCH better to CYA and play by
    the rules!
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    re-last
    
    I know they will not arrest me.  Things being what they are, I am
    quite shure they have no means to, nor plans for enforcing a regulation
    such as this---beyond the scope of sanctioned field or events; 
    It would take far to great an effort and vast resources.  I realize
    the potential benefits and will, of course, obey the regulations;
    I was just funnin' ya'.
    
    :-)
    
    Fred

Make sure that the 133s have enough torque for your application. They're "cute" 
(read small) but they don't have the torque of the cheaper standard size 148s.

I just claim that I need less ballast when I fly my glider with "standard" servos

;^)

    Just wanted to point out that the 1991 R/C frequency allocations
    will allow odd numbered channels to be inserted between the existing
    even numbered channels. At present each even numbered channel is
    20 KHz away from the adjacent channel. Therefore, in 1991 each channel
    will be separated by only 10 KHZ. This change occurs only within
    the 72 MHZ band. Cars and boats are in the 75 MHZ band so are not
    affected. 
    
    If your receiver is selective enough to see only its assigned frequency
    without being bothered by freqs. that are 10 to 20 khz away then
    you'll be okay. Likewise if your xmtr transmits only within its
    assigned freq. and is at least 35 db (or is it 55 db ?) down at
    10 khz away from center, then you won't be interfering with adjacent
    freqs. and will be 1991 "legal", a misnomer as legality has nothing
    to do with it.
    
    The sum total of all this is: if you fly by your self, away from
    all other r/c ers, 1991 has no relevancy. As you increase the number
    of flyers in one location, 1991 becomes more and more relevant,
    until you reach a situation where all 1991 channels are being used
    at one time on one field. If that ever happens you'd better d*amn
    well hope you have good narrow band equipment, MA list or not.
    
    Terry
    

>         <<< Note 105.212 by ELMAGO::TTOMBAUGH "High Plains Drifter" >>>
>                    -< Much ado about nothing ....or not? >-
...
>    The sum total of all this is: if you fly by your self, away from
>    all other r/c ers, 1991 has no relevancy. As you increase the number

Between the even and odd numbered AMA frequencies are the BEEPERS (paging
systems).

Our transmitters by law must put out .75 watts or less.  The BEEPERS
are running 500 watts.  It is interesting to note that they are not
required to wait for 1991.  There are several high powered BEEPERS in
service all over the country right now and more every day.

So you must not only be away from all other RCers but you must be FAR
FAR away from all known or proposed BEEPER stations.  See if you can find
an area of the country there they don't have Doctors or Waitresses. 

Gotta go - my boss is BEEPING me.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    re. last few
    
    Good point about the beepers, I'd forgotten about that. However,
    when using a fancy H-P spectrum analyzer at our soccor field flying
    site, which is across the street from a medical complex, and line
    of sight (12 miles) from TV chan. 4, we never see anything on it
    except Chan 4 which is a biiiig spike right alongside 72MHZ. Several
    people use chan 20 regularly, and I've never heard of any problems.
    So until further notice I'm not paranoid, but stay tuned :^).
    
    Terry
    

Keep in mind that the tv4 & ch20 interference was a harmonic at 460 which blows 
away the 455 intermediate stage in single conversion rxs. You won't see a spike 
around 72mhz. This is why it takes all channels out of the air (in those cases 
where it is seen)


Jim (who's still paranoid)

Well, first of all, it isn't the odd-channels that are going to
make adjacent frequencies in 1991 a problem, its the adjacent
pagers.  Plunking a high power (500 watts is high power at that
frequency), highly modulated signal next door to our systems is
pushing the current technology of RC receiver design, though the
industry, at least Airtronics, has solved the problem with flying
colors.

As I understand it, the old +/- one channel rule is still valid,
for transmitters, though the requirements for a gold sticker make
this a questionable prospect. One thing to remember though is
that we aren't interested in changing just one channel, if we
have to move, we want to go 5 or 10 or more channels to get away
from a local station.  

But as has been stated many times before, 1991 is not about
transmitters, its about receivers.  We face two problems here;
the adjacent frequency pager, and the physically adjacent (the
guy next to you on the flight line) RC channels.

For adjacent frequency problems, the pager is the big one, since
if you can reject a 500 watt transmitter next door, you can darn
well sure reject a 1-watter a few Khz more away.  This is where
the selective circuits in use today really shine and these goals
can be easily met by most modern receivers (including single
conversion).   If our frequency changing problem were about
adjacent frequency stations, we would be home free to change
crystals +/- one channel (two channels if we're post 1991).

The physically adjacent transmitters, next to you on the flight
line, are the big bugaboo, since adding the odd channels only
increases the number of interferring combinations possible.  This
is all the image frequency, 3IM, and so forth, that we've talked
about before.  Only double conversion, only critical receiver
front end and IF filtering will solve this -- and this is the
rub. According to every test I've read, you cannot have the
capability to swap crystals and have bomb-proof front ends at the
same time. This is why we don't change frequency.

Now, I understand that when receivers are made, they are sorted
into "high band" and "low band", so a given receiver can be moved
in frequency within its band with little problem.  But in the
final tuning process the receiver is optomized for its channel,
and there it must stay until re-tuned.

Rumors abound about synthesized frequency receivers, and I expect
to see it from at least Airtronics in the next year or so.  Maybe
in another 5 years it'll filter down to something us low-lifes
can afford.  Until then, I believe the only solution is to buy a
module transmitter and a receiver on another channel to give us
the flexibility we need.  You can tell where my Xmas/birthday
money will be going for some time to come!

I currently have a transmitter with a frequency module, the
Airtronics MD7P; to change frequency I only have to plug in a new
module.  To say that the system is rock solid would be a gross
understatement, it is incredible.  Though I must admit that my
old Futaba/Ace AM system was solid too, until I got hit.

A few issues back our club newsletter (flying tigers) had the following table
of local (NH) commercial users. 


	LOCATION	USER		FREQ		RC CHANNEL
	------------	-----------	----------	--------------
	Nashua		Ingersoll	74.140		72.150 = CH18
	Nashua		Rand		72.240		72.230 = CH22
	Berlin		Ingersoll	72.380		72.390 = CH30
	Salem		Rand		72.400		72.390 = CH30
	Nashua		Isaacson	72.440		72.430 = CH32
	Nashua		Container	72.440		72.430 = CH32
	Concord		Zurbach		72.480		72.470 = CH34
	Concord		Steel		72.560		72.550 = CH38
	Nashua		Ingersoll	72.560		72.550 = CH38
	Salem		Rsand Ranor	72.600		72.590 = CH40
	Derry		Inc. Max	72.640		72.630 = CH42
	Lancaster	Cohen Max	72.760		72.750 = CH48
	Berlin		Cohen		72.900		72.910 = CH56
	Manchester	Ingersoll	72.920		72.910 = CH56
	------------	-----------	----------	--------------


Note that all of these are only 10Khz off of the RC channel center frequencies.

G. Schrader

    Out at the Ware field we have 3 novices that ARE flying ch20 radios.
    There hasn't been any interest in outlawing them and we seem to be far 
    enough away from Boston that we haven't had any hits (yet).
    
    I read somewhere recently that the dual conversion recievers will take
    care of this problem and as long as you're using a dual conversion Rx
    you're ok. Is this really true? With the recent demise of Charlie
    Nelson's Waco due to failsafing, I'm considering interference/radio 
    issues again.
    
    I've been keeping an eye on these ch20 guys and coming down as soon as
    they get started but they seem to be there as often (and at the same 
    times) as me. I'm interested in hearing arguments for/against this.
    we're 75-100 miles from Boston and in a valley so we seem to be
    protected but strange atmospheric conditions could cause a BAD day at
    the field

    Re: -1
    Jim,
    	Dual conversion receivers should be immune to the CH 20/TV4
    interference.  By the way, when the odd numbered channels start being
    used, we will have a new problem similar to this when two channels
    operating 23 channels apart are on the air.  The difference in
    frequency between 23 channels is 460 Khz which is close to the IF
    frequency used in most single conversion receivers.  This interference
    product will cause interference with these older receivers.  The use of
    these odd numbered frequencies will probably cause the old receivers to
    be too unreliable to use.  THat fact plus the fact that pagers are
    blasting out big signals only 10Khz away from ours will force us to
    upgrade to new equipment. (Which I strongly support doing!)  We have an
    obligation to use the safest equipment available to reduce our exposure
    to liability and loss of flying fields.  This will cost all of us some
    $$ and require us to put usable equipment on the shelf, but it's still
    the right thing to do!  The end result will be fewer unexplained
    crashes due to interference.  I hope most in the RC hobby will
    understand this and accept the cost rather than force their clubs to
    sanction the use of old equipment and ban the odd frequencies.
    
    Charlie
    

    Thanks Charlie.
    
    I'm going with the better stuff myself but there are still those in the
    club that will expect to be able to fly the old stuff and I need to cover 
    the justifications in a january newsletter.

    I'm with Charlie. People have had PLENTY of time to prepare for
    1991. If they chose to wait, or thought it was going to be nothing,
    they will now unfortunately have to bite the bullet.
    
    In one sense, the problem will take care of itself because those with
    non 1991 equipment will be getting shot down all over the place. A
    club, however, has the SAFETY aspect to consider. Can we legitamately
    allow someone to fly knowing there plane could go out of control at
    any time. Where is it going to crash????? On your car????? On my
    car???? Worse yet, who might it hit??????? There is a definate
    liability issue here.
    
    I know we'll probably catch a lot of flack, but in my opinion clubs
    should NOT ALLOW non 1991 equipment to be used as of 1 January, 1991.
    The only possible exception might be a 3 or 4 month grace period, which
    is most of the winter when there's hardly any flying going on anyway. 
    Come spring...........be ready or be grounded.
    
    
    Steve

    I wrote this for my club newsletter to provide a background of
    understanding for the membership for decision making.  The next step
    will be to draft some alternative policies, but this note was intended
    only to provide the technical background.

    Your comments are requested.
    ---------------------------------------------------------------------

Radio topics:                                                        
=============
 
   Last month I mentioned how RC channel 20 (21 also) combines with
   TV channel 4 to create a Typhoid Mary, a flyer who can, himself,
   fly safely but is a threat to all the other single-conversion
   receivers in the air.  People using channel 20 should have their
   frequency changed, and people flying old or new single-conversion
   receivers should worry if there is a channel 20 pilot around.  I
   forgot to mention that some stores that have made the mistake of
   stocking channel 20 systems will try to dump them on the unwary.
   One of the local stores recently did just that to someone I know,
   perhaps in innocent ignorance of this problem.
 
   The same effect, the mixing of two transmissions about 22.75
   channels apart (TV 4 is effectively at RC -2), can occur between
   two RC channels once we start seeing the odd channel numbers this
   spring, and it can occur between any RC channel and a pager at that
   spacing.  (Pagers are at the half-channel positions such as 31.5
   and 32.5.)  This effect is sometimes called 2IM, and it is always
   characterized by Typhoid Marys.  The only real defense is a dual-
   conversion receiver.
 
   Dual-conversion receivers also offer better protection against
   "image interference" sources.  If you fly with a single-conversion
   receiver, you might experience interference from a single
   transmitter 45.5 channels away from your radio.  Except for the
   pagers, this is probably not a major worry and even then only
   sometimes worrisome.
 
   However, the pagers can get you with direct jamming.  They sit
   between our channels, halfway between the odd and even channels,
   potentially more close to you than an odd frequency RC transmitter.
   So there might be a pager 10 kHz away from your frequency, maybe
   two, one on each side.  The pager might be a fair distance away,
   but he is pumping out 300 times as much power as our transmitters.
   There are other significant factors such as antenna orientation,
   but sooner or later Murphy will nail a wide band receiver.
 
   One final word on receivers.  Some ads in the magazines are
   stretching every innuendo they can find.  Ignore the CLAIMS to be
   narrow band; usually only the advertised TRANSMITTERS justify the
   phrase.  And the phrase, "triple tuned" is rather meaningless; all
   dual-conversion receivers have three stages of filtering, but three
   stages of filtering does not imply dual-conversion or even narrow band. 
   Look up the monthly listings in Model Aviation to learn just which 
   receivers and transmitters meet the new standards.
 
 
   The bottom line: buy (or covert to) a dual conversion, narrow band
   receiver, preferably FM (or PCM) and a gold-stickered transmitter.

>   characterized by Typhoid Marys.  The only real defense is a dual-
>   conversion receiver.

It is not clear that the JR ABC&W isn't also a valid defense.
 
>   Look up the monthly listings in Model Aviation to learn just which 
>   receivers and transmitters meet the new standards.

But - remember the specs do not include tests for the 21 channel (TV 4 & 20)
problem.  Some of the receivers on the AMA list are NOT dual conversion.

1.  AMA legal = gold sticker on Tx

2.  AMA save = above with receiver from AMA list

3.  Really safe = above but also insure that receiver is dual conversion.

4.  Really safe and still have friends = above and not channel 20

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

George Meyer's column in the December 1990 Model Aviation
contained an interesting tidbit.  It concerned an FCC ruling that
allows manufacture/import of wideband transmitters until March
1993.  This would seem to contradict the AMA plan for 1991, and
it does...the AMA will not allow wideband equipment for any
sanctioned event.

George goes on about why dual conversion is the best way to
operate in 1991, but the interesting sentences (emphasis mine):

"Since all RC transmitters have abut the same power, the effect
of the kP reduction will be relatively moderate and equitable for
flyers.  IT WILL HOWEVER, REDUCE THE SIDEBANDS OF THE
HIGH-POWERED PRS STATIONS THAT ARE BETWEEN OUR CHANNELS, 10 KHZ
AWAY...."

This means that the PRS stations will be subject to the same
narrow-band emissions standards as our radios.  My earlier
objection to 1991 was that since we must yield to any PRS
station, if one of our models is shot down and causes injury, it
will be impossible to prove that we have been interferred
with...since by definition, the law requires us to move to a clear
channel in the face of an adjacent PRS station.  We would always
be the culprits.

Well, up until now, the PRS stations could interfere into our
"clear" channel pretty much to their heart's content.  But this
new ruling now limits them to the same narrow band spectrum that
we occupy.  It will be impossible for a legally operating PRS
station to interfere with us.  Nice going FCC, and AMA!

>>  It is not clear that the JR ABC&W isn't also a valid defense.

    All right, you got my curiosity beyond a passive state.  I have never
    heard of ABC&W except in the context of JR ads, and 25 years ago I was
    a professional in the field, designing signal processing systems in the
    countermeasures and elint fragment of aerospace.  But I'm very, very
    rusty, and this COULD be a new development, so I followed up on this
    pesky unknown.  I called JR on my own nickel (no 800 for tech info).

    		***********************************
    		*                                 *
    		*  They won't say what it means.  *  
    		*                                 *
    		***********************************

    Not in meaningful words, anyway. They say what words the letters stand
    for, but not what the words really mean in this context.  "We don't
    want the competition to get a jump on us."  "This is typical of being a
    US distributor for a Japanese company; they won't even tell _us_." 
    "The Japanese won't even send us schematics except for segments we're
    having trouble with."  Well this might be extremely annoying, but it
    has some credibility with me, since I have seen DEC Reading once treat
    DEC Tewksbury the same way with less justification.

    They said it was patented.  But by definition, that which is patented
    is disclosed to the public in a way that makes it clear how a device
    works.  So I asked for the patent number.  They claimed not to know. 
    It might be that this is a Japanese patent only, not a USA patent.  Or
    that no patent has been granted.  I don't know.

    This is exactly how you would expect them to behave if this were all
    marketing mumble jumble.  My first reaction was that this was marketing
    B__ S____, like Futaba's "triple tuned", albeit technically different.
 
    But there might be something of value here.  He said enough around the
    edges to suggest the possibility of autocorrelation, either at the RF
    level or at the video level.  The information being transmitted is
    inherently redundant and slowly varying --- just the thing for a system
    trading off information bandwidth for immunity.  Some of these schemes
    risk having the receiver switch its loyalty to an interference source,
    but it might be that in our environment it pays to trade off a rare
    total disaster in favor of general interference immunity.

    The bottom line is that I paid my nickel, but I still don't know what
    it is.  And the idea of laying out $400 for a pig in a poke ......

    Rusty Ryder

    They do say the Rx is Ultranarrowband 10KHz, for what it's worth. 

>   <<< Note 1274.3 by ZENDIA::REITH "Jim Reith DTN 226-6102 - LTN2-1/F02" >>>
>                     -< Lets get all the numbers correct >-
>    Ummmm. Isn't it TV4 and (ch20 OR ch21) and any two RC channels 23 apart?

Not sure what exactly your saying here.

     TV channel 4 Audio is at 71.75 MHz,  Channel 20 is 72.190.
     The difference is 440 KHz.  Channel 21 is 72.210.  The difference
     is 460 KHz.  Also channel 20.5 is 72.200 with a difference
     frequency of 450 KHz.  Now you might wonder why channel 20 would
     bother since the difference frequency is 15 KHz away from
     our IF frequency of 455 KHz.  Simple - the TV Audio center 
     frequency is 71.75 but they are modulating it's frequency and
     are very wide band.  For what it's worth their Video is down at
     67.25 MHz and they are allocated everything in the band from
     66 to 72 MHz.

So why didn't this every bother us before?  Simple - channel 38 was our
lowest channel at 72.550.  So even if TV Channel 4 is really eating
up the band width and chewing up everything up to 72 MHz - if you
subtract 72.000 from 72.550 the difference if 550 KHz which is well
out of range of our old wide band (OWB) receivers IF strips at 455 KHz.

The interesting thing here is that channel 21 should be worse than channel
20 if you live near a strong TV channel 4 station.  If any paging system
comes up on channel 20.5 it might get interesting.  What might save
us here is the failure mode.  

If someone is at the field running a channel 20 transmitter near
the Boston area (near a strong commercial broadcast TV channel 4)
Their plane works fine.  People with OWB single conversion receivers
get shot down - but only when the guy with channel 20 is closer
to the plane then the guy with the OWB receiver.  So if the guy on
channel 20 is standing on your left you can take off to the right and
climb out OK.  Make a big turn to the left and as you turn to come
back - POW.

I assume that it would be worse with channel 21.  But since we seem to 
require that the mixing transmitter is physically closer to your airplane
than you are - perhaps a paging system might not kill us.  After all
when ever you mix two frequencies together either electrically or in the
air you also produce the sum and difference frequencies (second order
harmonics) - BUT at a much reduced power level.  For that matter the sums 
and differences and the original 2 frequencies all mix together again and 
form all the new sums and differences (3rd order harmonics).  But the
amplitude of this multitude of frequencies is much smaller yet.

Sorry - I'm starting to ramble...

>    23 times 20khz spacing = 460khz beat frequency

Exactly and a pager plus an RC transmitter is 22.5 times 20 KHz spacing =
450 beat frequency.

The paging systems are a real threat.  Several have supposedly been
fined for boosting their power beyond their license.  Why - money.
If they crank up the power they cover a larger area and can sell
their paging service to more customers with no increase in their
costs.  Greed - but they will need the extra cash for when we sue
them for damages.  Let's see - if my time is worth so many dollars
an hour to DEC then how much is my hobby time worth?  Times the hours
necessary for scale research, travel expenses getting a plane qualified
for the masters, glue, emotional distress.  If we can prove negligence
I think we can go for 4 times damages.  Hmmmmmmm - this scanner may
pay for itself yet.  

Of course WE are negligent for running a OWB single conversion receiver.

Let's see - who is negligent

1. Paging stations that break the law
2. RCers that use OWB equipment
3. Futaba for selling single conversion receivers
4. Tower for selling channel 20 transmitters
5. FCC for allowing this nonsense
6. AMA for not taking the FCC to court
7. Al Casey for not taking the AMA to court
8. Steve Smith for asking Al Casey dumb questions and distracting from
   his real duties of harassing the AMA
9. DEC for paying for Steve Smith's call

2001 Spread Spectrum - here I come.

End of Rambling


Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Very concise Kay. That's what I was saying but the previous replies
    seemed to be referring to 21 channel separation instead of 23 channel
    which causes the 460kHz beat frequency.
    
    Thanks for the TV4 frequencies. I hadn't actually seen them listed
    anywhere before.

re Note 1274.4  (soon to become 105.zzz along with this entry) by Kay

>>  only when the guy with channel 20 is closer to the plane .......
>>  ................................................  But since we seem to 
>>  require that the mixing transmitter is physically closer to your airplane
>>  than you are .................................

    I don't agree, Kay.  I would agree if you had said, "such that the
    signal inside the receiver were stronger than the intended signal."

    Here you have some effects on the signal strength in addition to
    the simple 1/R**2 separation.  First, the pagers are putting out at
    least 300 times as much power.  Second, and perhaps most important, the
    relative antenna orientations are by common practice working against
    the victim; the victim usually points his antenna towards his plane
    while his companions are usually pointing elsewhere and have the gain
    advantage.

>>  when ever you mix [sic] two frequencies together either electrically 
>>  or in the air you also produce the sum and difference frequencies 

    No.  Not in the air.  Not even in a resistor network or an antenna.

    Only in a non-linear device such as a multiplier or a diode or a class
    C amplifier. ---- i.e.  the guts of a receiver or a transmitter

>>  but they will need the extra cash for when we sue them for damages.  

    Good try, but you lose.  We are legally "secondary users".  If they hit
    us, we have no reasonable option but to move.  If we hit them, we MUST
    move.

    ---------------------------------------------------------------

    Jeff started a topic on club rules re frequency control.  The replies
    are instead consistent with topic 105, the 1991 topic.  I'll move them.

Yeah, I've groused about the "attrition cures all" policy in the
1991 notes file.  Like it or not though, its official AMA policy
as written in Model Aviation by George Meyers, Fred Marks, and
others.  Guess they're prepared to pay the freight if something
happens.

There was some talk about disallowing OWBAM systems from
insurance, but apparently the AMA can't legally do this.  Also,
the Old Boy Network of the AMA expressed displeasure.  So the
latest position is that they will not allow non-1991 equipment at
officially sanctioned meets and leave it to the clubs to set
their own policy, while still covering any damage from this old
equipment.

>>>  only when the guy with channel 20 is closer to the plane .......
>>>  ................................................  But since we seem to 
>>>  require that the mixing transmitter is physically closer to your airplane
>>>  than you are .................................
>
>    I don't agree, Kay.  I would agree if you had said, "such that the
>    signal inside the receiver were stronger than the intended signal."
>
>    Here you have some effects on the signal strength in addition to
>    the simple 1/R**2 separation.  First, the pagers are putting out at
>    least 300 times as much power.  Second, and perhaps most important, the
>    relative antenna orientations are by common practice working against
>    the victim; the victim usually points his antenna towards his plane
>    while his companions are usually pointing elsewhere and have the gain
>    advantage.

Technically you are correct - but empirically the observed failure mode
is just as I have described.  I reference the experiences of other DECRCMers
at the Drop Zone (and Crow Island?) - mainly Dave Hartwell who was the first
to make accurate observations and survive - thanks to his brand new PCM
entering failsafe mode.

>>>  when ever you mix [sic] two frequencies together either electrically 
>>>  or in the air you also produce the sum and difference frequencies 
>
>    No.  Not in the air.  Not even in a resistor network or an antenna.
>
>    Only in a non-linear device such as a multiplier or a diode or a class
>    C amplifier. ---- i.e.  the guts of a receiver or a transmitter

Can't argue with that since the observable results are the same.  That is the
only place you can observe the results of mixing is with a receiver of some
sort.  I don't have many books on EM theory any more so I yield to your 
expertise.

>>>  but they will need the extra cash for when we sue them for damages.  
>
>    Good try, but you lose.  We are legally "secondary users".  If they hit
>    us, we have no reasonable option but to move.  If we hit them, we MUST
>    move.

Lost the context - but if the pager folks are breaking the law by exceeding
their licensed power limit (according to rec.radio.shortwave they are) 
then they are negligent.

If the FCC assigns us "secondary user" status knowing that radio interference
can be life threatening then they are negligent.

Actualy I believe we were (are) secondary users before 1991 but with the 
new frequency allocations we are primary users altho we are clearly sandwiched
in between some power houses.  But nobody can use our exact frequencies
for anything except the control of radio controlled airplanes.  Right?

Any lawyer will tell you that Where there is negligence and danger - there
is money to be made.

Course this goes both ways.  We have all been alerted to the dangers of
OWB receivers and narrow band receivers without dual conversion.

Please add "I think" to the front of every sentence above and smiles :-)))
after every one.  I'm after all not a lawyer, electrical engineer or licensed
pilot - tho I have a deep interest in all three fields.  I'm just a BSCS
and ASEE with a 1st class FCC license and I tried to get into law school
at night but had problems getting DEC approval then the school was closed.
But that's another story and I'm really rambling now.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    I have an important question that must be answered. If any of you
    know (I mean KNOW, not speculation) the answer, please give it
    to us, otherwise I'll try to see if I can find out.
    
    The question:
    
    Does the AMA guideline for certifying "1991" receivers require
    that they be dual conversion, and NOT have a 455kHz IF, or does
    it just state bandwidth requirements?
    
    I have heard rumors that one or more receivers on the AMA 1991
    list are not dual conversion, just well-tuned single conversion.
    If the AMA does not specifically test for 2IM susceptibility,
    than the TV4 experience proves that the 23 channel problem WILL
    occur. But, enough rumors - anybody got FACTS?
    
    Dave
    
    p.s.
    Oh, and Kay - good luck trying to sue the FCC for damages!

    Dave,
    
    JR's ABC&W receiver is NOT dual conversion but has received AMA
    certification.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    
       I have the same question as Dave. Specificaly regarding the Futaba
    R114H  AM reciever sold with the Attack radio. This seems to be a
    narrow band width single conversion reciever. It is also on the AMA
    1991 approved list. I have three of these radios. I am upgrading one with
    an RCD reciever that is already ordered.
       From what I can put together, it sounds as if the R114H reciever is
    approved to use, but probably not wise to use in the 1991 environment. 
    
                                                           DW2
    

    The R114H Rx is popular due to the Attack 4ch price and has been the
    entry radio of beginners at our club. This is an important Rx to
    discuss since there are so many out there and this is one of the Futaba
    AM radio upgrades.

If the receiver doesn't say "Dual Conversion" on it then guess what.
It is not dual conversion.  But don't take my word for it - call
Futaba at (714)455-9888.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    
     The R114H does not claim to be Dual Conversion, maybe it should read
    dual confusion :) :). The problem is that it still appears on the AMA
    1991 approved reciever list.

    It is narrow band and all by itself, it is fine. But get it into the
    2IM and 3IM situations at the typical club field and it has the same
    problems. It is a 455kHz single conversion Rx and will run the risks
    described.
    
    Keep in mind that the problem is the interaction of two OTHER Txs 23
    (or 22.5 in the pager case) channels apart, swamping your 455 stage
    with a 450 or 460kHz signal with something that falls into your 10kHz
    narrow band. If you are the offending 2nd Tx, the swamping will be with
    some component of your signal and will be less disasterous to you than
    others.

    The AMA's ICOM IC-R7000 scanner arrived yesterday, and I violated the
    first rule of DEC engineering; I read the instructions along with a
    copy of George Myer's column from the 8/89 MA.  This is a nice little
    machine.  Advice and tips on using it would be appreciated.

    Here in Mont Vernon, NH, about 20 miles from Manchester, 20 miles from 
    Peterborough, 20 miles from Nashua, and about seven miles away from
    Uncanoonuc where I think Manchester's pager antennas might be, I found
    the RF environment quiet.  Uncanoonuc is behind the shadow of Joe
    English Hill, and that might explain the silence.  Last evening I found
    five stations; one was clearly intelligible, but all were weak.  The
    intelligible station carried a message from the Keene area 45 miles
    away, so I might be getting nothing from Uncanoonuc.  Today I set the
    trap for any strong stations and caught nothing.  No wonder I never get
    a radio hit here.

    In the next few weeks I'll map out the nearby club fields.  The unit is
    designed to run off a car battery, so I have mobility.  I will also try
    to replicate a TV4+RC20 incident that I think I observed last summer;
    I've arranged to borrow the radio systems that were involved.

    The Narrow Band AM Futaba Rx is definately Single Conversion with a
    455 kHz IF.  Dan Miner's old crystals worked fine in one, so that
    proves that it has the same frequency IF.  It really bothers me that
    one of the most popular manufacturers has continued the use of these
    receivers when the only reason to do so is lower cost.  We'll soon see
    how well they work in the 1991 environment with 23 channel separation
    generating a 460 kHz beat.  I can't say it won't work but I would be
    skeptical.
    
    Charlie
    

    In my search for the TV4/RC20 phenomenon here in Southern New
    Hampshire, I ran a preliminary experiment yesterday.  I didn't 
    find TV4/RC20, but I did see hits on an AM Futaba R114H receiver.

    I have a friend's plane that we both thought had been hit by 
    TV4/RC20 last summer; it is controlled by a Futaba Attack on RC30AM.
    For experiment comparison, I used another plane with an Airtronics
    Vanguard on RC32FM; the receiver is a double-conversion, narrow band
    radio listed in MA.  

    Both planes were placed side-by-side 30 inches above the kitchen floor. 
    (Yesterday at 5 am, indoors was the place to be.) The associated
    transmitters were turned on and positioned 30 and 40 feet away.  The
    test transmitters were about 8 feet away and turned on singly; this is
    too close, but the experiment was a poor simulation of a take-off
    situation and a chance to shake out my test procedures.  All antennas
    were extended.

    I used four other transmitters for the interference tests: 1) Terry
    Sweeney's Futaba Conquest on RC20AM (last summer's suspected culprit),
    2) a Futaba FG on RC20AM, 3) a Futaba Conquest on RC24FM, and 4) an old
    Aero Sport on RC28.  All transmitters had gold stickers except Terry's
    and the RC28; these had none.

    After the 8 foot tests, I took all the transmitters to another room and
    tried again with very different results.

    Partial results:
                            RC30 R114H      RC32 nb. dc.       at 25 feet
                            ----------      ------------       ----------

    RC20AM Conquest             hit             OK              both OK

    RC20AM FG                   hit             OK              both OK

    RC24FM Conquest             twitching       OK              both OK

    RC28AM Aero Sport           severe          twitching       both OK

    all four turned off         twitching       OK              both OK


    I conclude that:

        I probably wasn't seeing any TV4/RC20 effects here.

        The Aero Sport is splattering.  

            (I used the ICOM for a crude check of its bandwidth; it is 19 dB
            and 16 dB down at plus and minus one RC channel off nominal. In
            contrast, the Vanguard is 100 dB down at half that deviation.)

        The Futaba receiver is more vulnerable here than the Airtronics.

    I got a call from one of our club officers last night and he said that
    the AMA sent out a ~20 minute tape that explains the insurance and the
    new radio environment. I won't get to see it until our club meeting
    1/13/91 but other clubs should also be getting them.

    I saw a question a while back but didn't see an answer to it.  I'm
    considering a PCM radio.  They are considerably more expensive than an
    FM radio with equivilent features.  What's the advantage of PCM.  I am
    told by my local hobbie shop that the carrier signal is identical and
    just as open to interference.  With PCM you go into failsafe when you
    get hit and with straight FM you get glitched.  They say it is easier
    to save a plane if you get glitched and have some control than if you
    go into failsafe in the wrong attitude because of the time delay of
    comming out of failsafe.  Comments? What makes PCM worth the money?

    As I understand it, PCM (Pulse Code Modulation) is "supposed" to be a
    more efficient method of transmitting coded information to the receiver.  
    As you were told, PCM _does_ utilize FM as a carrier and is thus eually
    susceptible to interference forms that would bother FM and, like you, I'd
    prefer a non-failsafe system.
    
    The only "real" advantage to PCM, in my opinion, is the programmability
    and the ease of setup afforded by the computer radios.  My Futaba 7UAP 
    1024 PCM makes setting up an airplane absolutely painless but, other
    than this feature, I'm sure I'd be just as happy with the 7UAF (FM)
    version.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    With PCM a "glitch" mainly a signal that does not last for any more
    than 10'ths of a second will NOT drive a PCM into failsafe. Of the
    PCM receivers that I know of they won't failsafe until " NOT ONE
    """SINGLE VALID""" signal is received for about .5 to 1 second.
    If once out of every second the RX receives a good signal (digitally
    encoded data packet) then all the pilot will see is a slow performing
    plane. Not one that is dancing wildly about the sky look'in for a
    place to crash. Interference on a FM set will result in the servos
    potentially going wild for the entire duration of the interference.
    With PCM, the worst thing that can happen is that it will failsafe,
    KILL THE THROTTLE, and hold or go to preset servo conditions that
    you program in. Yes it takes several 10'ths of a second to come out
    of failsafe but if all you had was 1/10 of a second left to recover
    after interferance, then I doubt that the extra 10'th that failsafe
    was on is going to matter. In fact you may end up with more time
    with a PCM system. Why, because PCM "kills the throttle" to idle
    or some preset state that you program in. If the planes mov'in slower,
    you probably have more recovery time. Plus in failsafe you know exactly
    what your planes doing at all times. It may be going straight into the
    ground if it failsafed while you were diving, but until the
    interference is going, thats what it's going to do, go straight into
    the ground. Not so with non PCM systems, you can't tell what may happen
    or where the plane may end up. Besides, most of us are probably flying
    sorta close to straight and level most of the time. Given the odds
    it will failsafe in a straight and level (or close to it) attitude.
    If the interference never gooes away them it will land somewhere
    soon enough once the throttle is cut to idle during failsafe. Bet you
    can't make that claim with a non PCM system.   It's worth the bucks.
    It can even save your but and other in the pits. Planes can get
    interference in the pits also. How would you like to see your throttle
    go wild due to interference when you least expect it...
    
    
     Yep, I'm sold.... It's worth the extra bucks.
    
    
    
    							Dave
     

    Well, let's see if I can stick my foot in my mouth here.
    
    PCM is supposed to be a more "precise" method of transmitting the
    signal. I guess the idea here is that the receiver can better
    distinguish the real signal from interference. In other words, in cases
    of light interference, a PCM receiver should be able pick out the real
    signal where straight FM may not and glitch.
    
    PCM also affords you the option of having failsafe. Now understand
    right up front that failsafe is another one of those religeous type
    things where people either swear by it or hate it. I have mine
    programed and enabled. As of yet, I have never had a plane go into
    failsafe, but I look at it this way. In cases of light interference
    where straight FM may glitch but still give you some control, PCM
    SHOULD be able to read that signal and not glitch or go into failsafe.
    If it does go into failsafe, one of two things will happen. If you have
    no preset failsafe, all the controls will freeze (hold last) until such
    time as a clean signal can be read. If the interference is bad enough
    that it can cause a PCM to failsafe, then a straight FM radio PROBABLY
    would have had full servo deflection on one or more servo's causing the
    plane to go out of control depending on which channel/channels are
    getting hit. Doing nothing is better (to me) then getting full aileron
    or elevator deflection.
    
    If you do have a preset failsafe programed, then if the radio goes into
    failsafe, the controls will automatically go to that preset condition.
    Usually it would be set up for a little up elevator, a little left or
    right rudder, and low throttle. SUPPOSEDLY then, if you got hit, your
    engine would go to low throttle, and your plane would go into a slow
    spiral. When you get your signal back, everything would return to
    normal.
    
    Also keep in mind that although the time is very short, maybe .3 of a
    second, the PCM receiver will attempt several times to read a signal 
    before it goes into failsafe. It's not just automatic.
    
    To me, if I'm going to get totally blown out of the air, I'd rather
    come down in some controlled manner rather than out of control, or
    have a flyaway. Other people will be just as convincing that PCM
    stinks.
    
    Steve

When I went about selecting a radio last year, I had considered
the Airtronics Vanguard PCM as the choice, the biggest reason
being the fail-safe feature.

But then I read a comment by George Meyers in Model Aviation to
the effect that the receivers tested to AMA guidelines, and
subject to every type of ADJACENT channel interference including
pagers, adjacent RC transmitters, 2IM, and 3IM had come through
with no problems.  In effect these receivers were bulletproof in
the full 1991 environment at its worst, therefore negating the
advantage of fail-safe.

I then thought about what would be next on my priority list and
selected the MD7 (no longer in production), a straight FM radio, 
as my radio.  I did this because I think that ability to change
channels is more important than fail-safe, given the above
evidence.  

Now, notice that I did emphasize "ADJACENT channel" above.  If
some bozo turns on your frequency, you're gonna be shot down, and
fail-safe will *possibly* save you.  I'll take the chance, since we
run a pretty civilized club out here in Coleraddy.  If I was in a
more populated environment, with flying sites open to the general
public like some of those in the east have to fly in, I'd
reconsider my choice.

For me, the computer go-fasts in the PCM radios are not
desirable, and not worth the extra money.  

    Thhe way I think of it is that the signal is checksummed. If it doesn't
    match the checksum, it's ignored, if it does, it's used. The FM box
    just demodulates and uses the garbage signal. If one frame is bad, it
    doesn't glitch the controls. Many times when the signal is getting
    interfered with you just notice slow reaction on the controls. Dan Snow
    was flying with a Tx in the impound on his frequency and just noticed a
    sluggishness. Is it worth an extra $100 on the price of the radio??
    That's up to the modeller to decide. I FEEL better knowing I'm using it
    and I guess that makes it worth it. Each person needs to decide on it
    for themselves.

i've been sold on pcm failsafe ever since my cub got shot down.
my 1/4 scale cub was flying straight and level 50 feet off the ground
when a guy with the same type of radio on the same channel turned on.
it was as if his radio completely swamped me out, the cub went to full
throttle and down elevator.  it was over in a blink.
had i had failsafe i believe i'd have had a good 20 seconds with this
plane/attitude to get the guy to turn off.  worst case would have been
gliding into some trees rather than trashing $200 dollars of equipment.

heres a question, if both our radios were identical pcm's, could his xmitter
take control without failsafing?  i doubt it.

however, my empirical evidence is far from perfect.
i flew my p47 for 20 flights on a futaba fm and never had a radio problem.
since the cub incident i've been flying it with a jr pcm10.  i have been locked
out on 2 occasions (that i know about).  both were very short in duration and
the only clue was once my drop tank dropped (programming error there) and the
other time i heard the throttle twitch.

what does this mean, i dont know?  maybe the futaba would never have skipped a
beat.  maybe with the futable the jug would have tent pegged in at 120mph.
its an imperfect comparison because the channels are different (maybe chanel
30 has more pager interference than 56?) and possibly the operating environment
is different too (more pagers than year before?).  both lockouts were with the
jug while other planes flying on the same xmitter and sometimes the same rx
have never had a bit of trouble.  the jug, with its vibrating bully engine and
10 servos connected with a half-dozen extensions/y-connectors, does seem to
stress the radio system more, especially when flown far distances away.

another MAJOR advantage of pcm is battery voltage.  i remember the time my radio
wouldnt let me throttle up my scooter.  the rx battery was dumping...

despite 2 hiccups, i will always spend the extra $50 for pcm each time i buy
a new rx.

kevin

    That's one feature I forgot about. I don't think it really has anything
    to do with PCM meaning that I would imagine a low rx battery warning
    could be built in to any rx, however it IS a feature on the Airtronics
    PCM.
    
    What happens is, when your rx battery begins to dump (but of course we
    all keep very close watch on the rx voltage right????) the rx will
    cycle the throttle to low and then back up to it's previous setting. It
    will do this every 60 seconds reducing the amount of throttle you get
    back every time. When it starts, you've got maybe 3 minutes to land
    before your rx battery completely fails. That's a whole lot better then
    no warning at all (except watching your pride and joy die).
    
    Steve

    I now have 2 Futaba 1024 PCM radios on the same channel. For the heck
    of it I decided to turn both transmitters on at the same time. One TX
    was near the plane with the antenna collasped. I had the other
    transmitter with the antenna partially extended. As I walked away AND
    moved that transmitter in different directions, I could get the RX
    to failsafe, and come out of falesafe. At no time did one TX take over
    the other. (this makes sense since 2 transmitters will combine to
    produce interference to the RX).
    
    One key point here is that by moving the TX around, at the same
    distance from the plane I could gain control of the RX. I've heard this
    before, and I tend to now believe that its true that if your getting
    hit it makes a lot of sense to move the TX such that the RX given the
    positions of the transmitter and RX antenna will once again pick up
    valid signals.
    
    
    
    
    							Dave
    

    Ok, so how about a simplified, but concise explanation?

    All FM radios use basically the same technique for transmitting their
    signals.  There's no difference between PCM and Non-PCM systems in this
    particular regard (they *DO* differ in the content of the signal,
    though).  Given two identical transmitters, one PCM and one not, and a
    common source of interference, both will suffer the same effects of not
    being able to get a signal through to their respective receivers as a
    result of that interference.  The difference between the two types of
    radio systems is in how the Receivers react to the loss of good signal.

    Non-PCM systems (often referred to as PPM, or Pulse Position Modulation,
    as opposed to PCM, which is Pulse Coded Modulation) cannot distinguish
    intereference generated signals from legitimate signals.  As a result, a
    PPM system will attempt to respond to an interference source in the same
    way it's supposed to repond to a legitimate source.  Since the
    interference will invariably contain random information, when this
    signal is interpreted by the Receiver the results will be random action
    by the servos.

    PCM uses a digitally encoded number to convey desired servo position to
    the receiver.  The receiver "checksums" the packet of data that contains
    the position information for the servos before it attempts to use the
    data.  If the checksum is invalid, the receiver will discard the
    associate bad data and wait for another packet.  The key thing here is,
    that while it's sitting around waiting for good data, the receiver is
    holding the servos in the position specified by the last valid data
    packet it received.  In addition, at the option of the user, a PCM
    system can be programmed to "failsafe" selected channels by moving their
    servos to pre-programmed positions when a loss of good signal occurs
    (but you don't have to use this mode, I don't.  I much prefer to have
    the servos hold their last good position and wait for valid signal to
    return).

    The primary advantage to PCM is that, in the absence of good signal your
    plane doesn't start spazzing about all over the sky or into the ground.
    It holds it's last heading and attitude (optionally with some
    preprogrammed change to some or all of the channels) until the good
    singal comes back.  In a environment where interference is a problem,
    this makes you much more likely to be able to recover your plane without
    crashing.

    The case in point can be seen in a model Helicopter I fly.  My home is
    located near an airport, and some interference source comes along every
    once and a while when I'm hovering in my front yard.  I had an FM-PPM
    style Radio in the Heli, and when the interference hit, the Heli would
    "twitch", sometimes quite dangerously, in a few instances almost flying
    itself into the ground.  I've upgraded to a FM-PCM radio (by the same
    manufacturer, JR, as the older FM only radio) and now fly trouble free.
    Every once and a while I notice the Heli is a little slow to respond,
    and I know I'm being "hit" by interference, but I don't have to worry,
    it's hardly even an inconvenience.

    Randy

RE: 105.292

Very interesting. I'd always assumed that because things happen so quickly with 
helicopters that PCM wasn't very helpful for this specific case. Based on what
you say. I see the errors of my ways. 8^) The next radio will have failsafe.

    Well, I never expected to get that many responses so quickly.  It looks
    like the pro-PCM guys are very strong.  The arguements sound strong for
    PCM.  The only discrepancy I saw is I was told locally that once a PCM
    radio goes into failsafe it takes 3 seconds after signal restoration to
    get control back, not fractions of a second.  I am aware this may be a
    case of exageration.
    
    It is true that the throttle reduction capability can be done without
    PCM. In fact, about 15 years ago I bought a product that inserts
    between the receiver and the throttle servo and monitors both battery
    voltage and signal.  If either gets too week it reduces the throttle to
    an adjustable preset.  It has saved many a plane.  that device alone
    cost me as much as the difference between an FM and a PCM radio.
    
    I guess I'm sold on the benefits of PCM.  Thanks for all the input, it
    was a real education.

    
    >>> 3 seconds after signal restoration to get control back.
    
    I highly doubt it. If I turn my xmitter off and force the receiver
    into failsafe, I have control back within about a half second after
    power is restored.
    
    Steve

    Thanks, I wanted to try that in the hobby shop but the batteries were
    dead.  Makes more sense.  3 seconds without control is an eternity and
    I was skeptical.

    I agree with the earlier responses, but there are reasons why I, for
    one, bought FM, not PCM.  It was part of a planned series of purchases
    of compatible systems.  The plan involved buying multiple systems on
    the same frequency at a time when flight subsystems were awful
    expensive.  I couldn't afford to buy several high end systems or even
    the flight subsystems for a high end transmitter, so I decided to buy
    one fancy PCM system and let the others be [complete] low end systems. 
    If the fancy transmitter were to be compatible with the low end
    receivers, I'd have a good plan --- albeit with all the eggs in one
    [frequency] basket.

    The PCM systems tend to be incompatible with each other, sometimes even
    within one manufacturer (e.g. Airtronics Vision vs Airtronics Vanguard).
    However, except for Futaba, the PCM transmitters tend to be compatible
    in FM mode with other model and brand FM receivers.  (Futaba FM
    evidently is inverted with regard to other manufacturers's FM.)  So I
    started buying Airtronics FM systems and receivers.  My high end system
    will be a JR X347 PCM on the same frequency as the Airtronics systems.

    This will give me fancy capability on several planes at a reasonable
    cost.  I can get away with it because I fly in an area where the nearly
    bullet-proof Airtronics FM receivers never seem to get hit.  The JR
    receiver will be PCM with failsafe enabled.

    There are drawbacks.  Sources of on-frequency interference such as
    back-mod 3IM will get all of these systems including, I believe, the
    JR, but only the JR will have failsafe.  Only the 7 channel JR will
    have more than 6 channels.

    Alton who believes there are no perfect strategies here

    Alton,
    
    	I would be interested in hearing the reasons for your apparent
    reversal on the JR ABC&W receiver in the 1991 environment that would
    cause you to invest your hard earned money in an X347.
    
    Steve

    For what it's worth, I do have a X347.  A friend of mine ordered a JR
    Max-5 heli radio mailorder, and to his chagrin, got channel 20.  I live
    where there's enough TV channel 4 to watch the station without a
    problem.  With his transmitter turned on I have no trouble with my Tx &
    Rx.

    I don't know about the JR specs, but empirically, the X347 and PCM Rx
    seem to be good enough to avoid the TV4/RC20 problem.
    

    Randy

re  .-2      -< A change of heart????? >-
>>  the reasons for your apparent reversal on the JR ABC&W receiver ??

1.  I don't believe there has been a reversal.  The term I used last
    November was "a pig in a poke", meaning an UNKNOWN, not a "pig" in 
    the pejorative sense. I had first hand experience with the technical
    people at JR playing cozy with the explanation instead of being candid
    about why the receiver was as good as they claimed.  As long as it was
    an unknown, I was wary. I get extra wary when I think the marketing
    guys are trying to lay a smoke screen.

    I now think I understand what they are doing.  It is reasonable and
    consistent with the objectives, and I am less wary.  I will *remain*
    slightly wary until I take one apart and verify my understanding.


2.  Conjecture: I believe they are using a mixer with low cross-modulation
    products and then using RF AGC to keep the signals in the linear
    regions.  This conjecture is somewhat supported by one of the
    columnists.  If this conjecture is correct, there is no good reason for
    the marketing people to be coy; the technology is OK --- it doesn't
    need a smoke screen --- and it is not  a matter of competitive secrecy,
    that technology dates back to the 1940's, along with dual conversion.

    The effect of this approach, if it were to be true, is to minimize the
    interaction of multiple signals in the input --- e.g. TV4 and RC20.
    That keeps down the "2IM" sensitivity.  The linearity also helps the
    internal 3IM, although it doesn't do a thing for back-mod external 
    3IM.  (Neither does dual conversion.)

3.  Disclaimer:  This is conjecture.  I haven't seen JR's test reports.
    (I *have* seen the Airtronics reports.)  I couldn't get non-marketing 
    answers from JR, and they don't distribute circuit diagrams.  So we all 
    guess, or [like most people] we ignore the technology questions.  If 
    I buy one, I might just dig into the RX and settle my curiosity as I
    void my warranty.

4.  It is really the X347 TX I will buy.  The dominant use will be in
    FM mode with my Airtronics receivers.  I had even considered buying 
    the system and then selling the receiver and servos to cut my expense.
    For my uses, the TX seems to be the best TX on the market, and I like 
    the Airtronics receivers.  I'm not elated about having several brands 
    of servos around, although since I recall that Eric thought/thinks(?) 
    highly of the JR servos, it might make sense to retain them.

Alton

    I agree with most of what has been said in the last bunch of notes
    about the difference between FM and PCM (FM).  Most PCM receivers come
    out of failsafe as soon as they get ONE good frame.  The frame rate is
    only about 10 per second with PCM, so it could take UP TO .2 second to
    get one good one through.  In the scheme of RC control, that's not even
    noticeable to anyone but an Expert.  The frame rate with FM is usually
    20 hz so the servos update twice as often with FM as with PCM. 
    However, it is easy for a momentary glitch to cause servo movement. 
    The decoding process for FM requires the receiver to syncronize itself
    to the frame which consists of a pulse for each channel.  The sync is
    done by measuring the time difference between the first pulse and the
    last pulse which much be much longer than the time between channel
    pulses.  If you get another TX turned on, you get both sets of pulses
    comming in assyncronously.  This messes up the circuit that decides
    which channel gets which pulse.  Guess what happens when the full
    throttle pulse goes to the elevator channel. (You get full elevator
    travel either up or down)  If it happens for several frames, the servos
    move all over the place.  C R A S H
    	With PCM, each frame is checked to see if it is valid.  If not, the
    last frame is held - the servos do not move.  If no valid frame is
    received for some timeout period (programable on some radios like the
    X347), the receiver goes to failsafe mode and puts out some previously
    programmed pulses to the servos.  Once a valid frame is received, it is
    sent to the servos.  You can often fly through interference with PCM
    and not even know it.  Once it goes into failsafe, you usually have
    time to yell out your frequency and possibly get the interference to go
    away.  (Other guy turns off his TX on your frequency)
    
    
    For Fast Aerobatic ships, PCM is worth it for safety alone.
    For valuable scale ships, PCM is worth it for peace of mind.
    For trainers and sport planes, FM is probably plenty good enough.
    
    I have two PCM receivers and two FM receivers for use with my X347.
    
    Charlie
    

     I don't mean to change the current discusion going on but I had to
    enter this here. I'm one of those guy's who hate to see thing go to
    waste. I have a Tower Hobbies radio that's about 5-6 years old. With
    the resent change in equipment this year meaning Narrow band,2im,3im
    interference I decided to send this radio to a company called Kraft
    Midwest Inc. I was very imprest with what thy did I just got the
    radio back after about 5 weeks. First It cost me $154.00 (I have 2
    flight pack for this radio). They replaced the 2 Rx's for 2 RCD
    Ultra Narrow band,Pager proof & X-Tal filter,dual conversion AM Rx's
    which cost $69.95 apiece. They also narrow banded my Tx for free and
    cycled my batteries and basicly did a complete check out of the whole
    system they also replaced all servo leads for both flight packs 13
    servos all together. I for one am very satisfied the the results and
    the quality of work. So for you guy's out there that have old radio's
    and don't want to trash them this might be a good alturnative. I will
    post the address below (not sure if it is any were in this
    conference.). I also can send a copy of the brochure they sent me to
    anyone who what's it.
    
     
                          Kraft Midwest Inc.
                          115 E. Main,Northville,MI 48167
                          phone:(313)348-0085
                          FAX (3130 348-4175
    
    
    
                                        KEEP'EM FLYIN
                                        Jerry Evers

    I have a friend that went this route with a Kraft Sport 5ch he had. The
    radio works very well.
    
    One word of warning/advice: If you have marginal/bad batteries, replace
    them before you send it in. He got a call about his being bad and when
    he refussed to pay their inflated battery prices, they said that they
    wouldn't warrenty the work they had done because he would have to
    reopen the Tx. Pop for the <$10 Sanyo packs if you're in doubt (their
    Rx pack was something like $25 so he told them to keep it)
    
    Standard disclaimer - you mileage may vary

    Jim
     I'm awere of that but I just replaced them this past summer but
    it's nice to know that they were cycled before the flying season.
    
    
    
                                         Jerry Evers

    Just gave Airtronics a call today, looking for my 4 channel Vanguard
    that they have taken hostage. They got it Jan. 22 for an upgrade, and
    there it sits. The woman who answered (very pleasant, by the way) said
    that the holdup is the RF modules, so the radios are stacked up waiting
    for the next shipment. She seemed surprised that so many people sent
    their radios in at the stroke of 1991 when "we've been offering the
    upgrade for two years!" If they are truly surprised, they know nothing
    about human nature. She said she'd call me back when she knew the
    schedule of RF module shipments.
    
    Dave
    

    Well we seemed to have a 23 channel seperation problem (2IM ?) today
    with the Futaba R114H receiver.  I am on 52, the other guy on 29 and we
    are flying Futaba Attacks, both bought in 1991.
    
    I thought I had a rx battery problem as it my plane sometimes did not
    respond at a distance.  The battery checked out OK, so the next thing
    I tried was a ground distance check with the tx aerial down.  It
    sometimes did not respond and once got stuck.  Then we realized that we
    were 23 channels apart.  
    
    My receiver has a silver sticker with the words:
    
    	Narrow
       	-------
    	|20KHz|
    	|1991 |
        -------
    	 Band
    
    This has made me a dual conversion convert.  I was thinking of buying a
    second flight pack for my other plane but now I am going to buy a
    complete FM Dual Conversion package, probably from Airtronics. 
                                                    

    I completely agree with your decision to buy a good double conversion
    system for your next radio, but you might have a correctable problem
    here.  You should consider pulling the receiver and sending both RX and
    TX back to Futaba for warranty service after first gathering a bit more
    data.  That useful data is a determination of the impact of your
    companion's transmission on your reception.

    If your radio were working as designed (albeit a poor design), then
    *your* receiver should not have been affected by the 23 channel
    separation.  The IF generated in your mixer depends upon the amplitude
    of both mixing signals, one of which is supposed to be the local
    oscillator, not the other transmission.  If your local oscillator were
    to have a fault, then the spurious IF might be comparable to the
    intended IF; that would be a correctable fault; if this is the case,
    you should have worse problems when he is transmitting than when he is
    not.  If your transmitter or another aspect of your receiver is
    malfunctioning, then your problems should be almost independent of his
    transmission.

    Can you rejoin him at the field and run more tests?  If you do, pay
    attention to antenna orientation while you gather data; it might be a
    factor.

    Alton

>   <<< Note 105.307 by ABACUS::RYDER "perpetually the bewildered beginner" >>>
>                    -< probably an ATTACK problem, not 2IM >-

Alton, why don't you think it is a 2IM problem?  What about this
case excludes it from being the classic example that we've been waiting
to see?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Kay,
    
    	If it's a 2IM problem and the radio hardware is functioning
    correctly on both radios used,  why isn't it a 2IM problem for
    both radios?  Greated Alton was 23 channels from the other guy
    but in the reverse, the other guy was 23 channels away from Alton.
    Why weren't both sets effected?
    
    
    Tom
    
    P.S. I'm happy flying JR:-)

>>  Alton, why don't you think it is a 2IM problem?  

    We generally use the term, "2IM", to refer to the TV4/RC20 type problem
    or the "23 channel separation problem" where two signals about 455 kHz
    apart generate a false IF of this difference frequency in a victim's
    receiver.  There are three characteristics of 2IM:

    	The two culprits shoot down *other* systems, not their own.

    	The victims have single-conversion receivers [with 455 kHz IF's].

    	If either culprit turns off, the problem goes away.

    The obvious question, implicit in yours, is this: if the spurious
    mixing occurs in a third guy's receiver, does it not also occur in 
    the receivers of the two culprits?  I believe it does, so the next
    question is "Why doesn't it cause a problem for them also?"

    I'm not sure.  The answer I've been given is that since the modulation
    of the resulting IF is a complex combination of the two input signals,
    and   **since one of the two has the desired modulation,**   the evil
    isn't as bad as when neither signal has the desired modulation. 
    Whether this is correct or not, from what I've read the culprits don't
    have problems themselves, only their innocent companions.

    Note that the original note said nothing about the impact of turning on
    and off the second transmitter.  The problems might have nothing to do
    with the other guy.  The original note implied that as soon as they
    realized that their separation was "23 channels apart" (=460 kHz), they
    believed they had identified the source of the problem.  My note was
    intended to cast doubt on this conclusion and to get more data.  If
    Richard Taylor's system has a fault, it would be good to get it fixed.

    Alton

    I did not want to say it, but the other guy was having problems as
    well.  On the other hand, it was his first days flying (it was about my
    5th), and he had the control throws set on the wild side.  He managed
    an outside loop and some inverted flying on his first flight with a
    Spirit glider.  I have not got my Gentle Lady upside down yet (except
    on a landing).  Anyway, he has some strange behaviour as well, but I
    cannot remember if I had my transmitter on when they occured.
    
    After we made the initial diagnosis, we just decided not to have our
    transmitters on at the same time, but on reflection, I think we should
    try some more experiments.  When we do that, I will report back. 
                                                                 

    You don't need a third plane to have the 23 channel problem.  I don't
    think you will get any satisfaction sending the R114 back to Futaba. 
    They'll probably just send it back and say it checks out fine.  All of
    these receivers should suffer from 2IM.
    
    Charlie