Conference vmszoo::rc

This note is getting stale.

What radios look bad on the spectrum analyzer?

              _!_
Bye        ----O----
Kay R. Fisher / \
 
==============================================================

Nobody has said.  The magazines all have a policy of not saying
anything bad about specific products.  Protecting the advertisers
and all that....Anyway, what I did gather was that the ones that
failed were the older and less expensive types.  I don't know if
this would include some of the low-line Futabas, for instance (I
have an old and low-line Futaba).  What I plan to do is to take
my transmitter to the Nats, even though I won't be flying RC, and
get it checked.  I suspect that in the near future there will be
more opportunities to get our radios checked.  

>Which radios are clean and which are dirty on the spectrum analyzer?
>

Well - I called Hobby Radio in North Carolina and asked the guy there
which radios are clean and which are not.  He talked at length about
various radios and below is a summary as best I can recall.

Futaba 		= Good (1991 Versions Good also)
JR	 	= Good (1991 Versions Good also)
ACOM		= Good and clean for an expensive radio
World Engines	= Bad
Challenger	= Bad
Airtronics	= Good - just barely meeting 1991 standards and
		  not yet type approved by the FCC to his knowledge
ACE		= Excellent (But he is an ACE dealer)
Cirrus		= Bad
CHC (Consumers Hobbie Group) = Bad

Soooooooooooo bear in mind that this is my overall feeling after talking
at length about radios in general.  If you have a world engines radio
it is probably a fine set - but if one of our planes crashes because
of noise interference then at least one expert believes your may be at fault.

He is going to send me an ACE catalog and I will make some copies available
to interested parties after I get it.

If your concerned call this guy at (919)291-8548.

Please don't give him and me alot of bad press for posting this.
I am just sick of magazine articles that only praise whatever they
test.  Kinda like the "Car of the year" concept.  One year a reliable
magazine editor will say that this year there were no new cars worth
mentioning.  Ever see a news program where they cut to the sports early
because there was no news?

From talking to this guy I think the consumer reports article would
have ACE as the BEST.  JR as the Best Bargain.  Futaba as the safe secure
standby and Challenger as not acceptable for safety reasons.

              _!_
Bye        ----O----
Kay R. Fisher / \
 
==============================================================

Thanks for getting that info, Kay.  From your reply it was
unclear to me if the "clean" and "dirty" was with reference to
meeting current bandwidth and interference standards, or if it
was to 1991.

I agree with that assessment of ACE.  They say that the Silver
Seven is not 1991, but I'll put my money on it any day.  That's
one good company.

Clean and dirty are in general - not just 1991 since most of the radios aren't
up to 1991 standards yet.

Futaba, JR, Airtronics are good (clean) with both their old pre-1991 models
and the new 1991 models.  Ace is clean in both but they only have 1991 receivers
so far - no new 1991 transmitters yet.  Buy the way the guy mentioned that
the new ACE 1991 receiver is slightly larger than previous.

              _!_
Bye        ----O----
Kay R. Fisher / \
 
==============================================================

    Should I read from the notes that my spanking new EXPERT (World
    Engines) 7 Ch toy is going to cause grief to others or are we talking
    about other models.

                                                                     
    md

 Grief is relative.

I'm sure it meets specs otherwise they wouldn't be allowed to sell it.

The thing is it apparently is only worth what you paid for it.  Not much
for a 7ch FM.  It is certainly a good idea to always watch the planes in the sky
when you first turn on your set.  That is a good habit with any radio.  
This assumes of course that your darn sure that you're not sharing a frequency
in the first place.  This weekend I saw a scale ship hit the dirt as soon as
a new flyer turned his on.  It turns out they were wildly different frequencies
and I think the problem was the lightening storm - but the guy should have
been watching the sky when he applied power.  If for no other reason he missed
a nice crash.  More on the scale competition in a different note.

If I had your radio I wouldn't worry about a thing.
But if I was shopping (and I am) then I would (am) put a lot of
weight on what this experienced radio repairman told me.

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

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

    re .-1 & WE EXPERT 7ch: 
    
    "Not much for a 7ch": Refers to worth or price ? 
    
    No, I have not any problems with it. I've been very careful about
    what I do when turing transmitter on. I usually do a check by turning
    the receiver on first. 
    
    I've seen cases where two guys are flying ok then a third turns
    his transmitter on a different frequency on things start to go
    south for at lest one of three.
    
    md7

                I'm getting  pretty  concerned about CH 56 as a result of
        several hits over  the past caouple of months.  What hot the nail
        on the head was  yesterday when I suddenly got hit, recovered and
        started brining the plane in when I got hit again and it nozed in
        from about 50 feet.  My  ACE  bibe was crushed back to the second
        bulkhead, can be fixed up for next weekend.    10 minutes later a
        guy  with  a  MIG 23 on the same channel  had  exactly  the  same
        experience, but the MIG was completely destroyed.  The experience
        we both  had was that we would lose control, get it back and lose
        it again.  This  is  the second time I have a serious crash under
        these circumstances, so I have had it.
        
                The question is:    Is it because CH 56 is at the top end
        and something (what's up  there anyway, CB?) above the RC band is
        hitting  us?    It seemed exactly  like  someone  was  hitting  a
        transmit button and releasing it again.   I was only 50 feet from
        the plane when the fatal hit was received,  and  the  other CH 56
        transmitter was definitely off.
        
                The second  question  centers  around  prevention.    I'm
        seriously considering purchasing an FM or PCM radio and moving to
        another channel.  50 doesn't look too crowded on my field.  Would
        that make a significant difference in  the probability of getting
        hit?  The Airtronics modular system looks  good, is claimed to be
        1991 and has a lot of features I like. Any experience with it?
        
        Thanks/Anker

Sounds like you got hit with a paging system.  The communications
consisit of very short transmissions.  Bottom line is that 56 is
a bad channel for your field.  Theoretically, if you had 1991
equipment, you would not have received the hit.

Another possibility is that you were hit with 3IM.  That is
third-order intermodulation interference.  It happens when two RC
channels, neither of which interfere with each other or with the
third channel by themselves, create a beat frequency that
knocks out the third channel.  MA has had recent articles giving
the matrix of 3IM channels.  The new radios are supposed to be
more resistant to 3IM.

I would vote that you got a paging system hit.  There are no CB
channels near the RC band, but some guys, running illegal power
(they have put out up to 1KW MOBILE) could get you, since anyone
stupid enough to do that also is stupid enough to not care where
his harmonics are.   That is a remote possibility.

    How about some more details...  what field were you at, how many
    other planes were in the air (52 and 54 would be good 3IM candidates),
    what was the weather like, what time of day, etc.
    	I've been shot down by 3IM and found that it was only when things
    lined up right that I got the hits - unfortunately one of those
    times was at final landing approach 20 feet off the ground.
    	Just a general observation about our field in Westboro Mass...
    It seems that people have more interference problems on clear, dry
    days.  I remember a particularly bad day last autumn that lots of
    frequencies seemed to be having trouble.  Maybe interference signals
    are travelling better on those days?
    	I had a Futaba on 56 for two years and never got hit in Westboro.
    My 3IM problem was with an Airtronics on 54 and was caused by my
    stupidity for not checking the other two fliers - who happened to
    be on 50 and 52.
    	Of course the other obvious possibility is that someone at your
    field has a transmitter that's out of whack.  Was anyone flying
    on 54 at the time?  I've seen a lot of cases where two adjacent
    channels hit each other without even the help of a third.

    Bill

        Re:< Note 133.13 by LEDS::LEWIS >

                It happened on the CRRC field in the Sudbury extension of
        Fort Devens.   The  best  field  I  know  of in terms of runways,
        distance from abutters, general discipline etc..
        
                There were two other  guys  flying at the time, one on 48
        and I'm not sure what  the  other  was.  When I yelled that I was
        being hot the more experienced guy  moved  away  from  me, but it
        didn't make a difference.  There were  a  couple  of  guys in the
        pits who had channel 52.  The probability  of  3IM  seems remote,
        particularly  since there was a different group of fliers,  small
        again, when the MIG got hit.
        
                The MIG was a real shame.  It's the only  ducted fan that
        I  have seen on this field and flew like a rocket.    The  impact
        broke it up into little bits, there wasn't a single piece of  the
        plane  that was intact.  I was lucky, no damage behind the second
        bulkhead, everything  gone  in  front.  I'm amazed that the wings
        both survived.
        
                Does FM make  a  big improvement, or is it a good idea to
        go all the way to PCM?
        
        Thanks for all the input/Anker

    In theory I would expect FM to be less prone to interference but
    in practice it does not really seem any better. I have been using
    one of the Futaba conquest PCM rigs with good results. PCM will
    generaly at least prevent violent control actions if you get hit.

Do not discount lightening.  Ever listen to a radio during a lightening
storm.  This time of the year there are lightening storms around the
area constantly.  I doubt if they have to be very close to shoot you down.

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

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

                I asked  Bob  Fischer yesterday and he confirmed what the
        previous notes have said.  FM gives a slight improvement, but PCM
        is the way to  go  for real protection.  The FUTABA 5 channel PCM
        system costs $229 mail order  and  $258  as Fischer's, so I think
        I'll go for that. The servos are lightning fast.
        
                Interesting thought, Kay.  I hadn't thought of lightning.
        I don't think it could have been. Sunday was very dry and sunny.
        
        Thanks/Anker

    RE: -.11 (GETTING HIT, RECOVER, GET HIT AGAIN)
    
    Sure sounds like a RCC Pager just set up shop on your frequency...
    Page a person, wait several seconds, repage.
    Spectrum scanner should verify this!

    
    FM is probably not the answer.  From what I've seen and read the
    FM systems don't work well when AM systems are around.  I've seen
    cases where the Airtronics CS7P-FM would not work with any adjacent
    AM transmitters on.  I'm not sure if they have improved the receiver
    front-end design since the first FM systems, but I definitely would
    not go FM with any of the older systems.

        Of course, PCM systems also use FM transmission (I think), so
    the real benefit of PCM systems may be that they can figure out
    when they are getting hit and ignore it (as mentioned in -.15).
    This doesn't do you much good if you're getting continuously hit,
    because the thing will just go failsafe and you'll still crash
    (though maybe a little less violently). I wonder if they also
    improved the receiver front-end design when they designed the
    PCM systems?
    
    	Anyway, getting back to your problem, the cause
    seems to be something transmitting on your frequency near the
    field.  PCM on that frequency might have the same problem!
    My suggestion would be to change frequencies, whether you stick
    with AM or go PCM.

    Bill