Conference vmszoo::rc

    Mark,
    	Most manufacturers will convert your RC rig to a different channel
    for a reasonable price.  Some people just swap crystals themselves,
    but this should not be done unless you have access to allignment
    equipment and a spectrum analyzer to check things out and retune
    the receiver.  (It is technically illegal to swap crystals without
    the proper certification.)
    
    Charlie
    

    Some hardware is type-accepted for user crystal frequency swaps; a lot
    of Futaba stuff is. (my car radio is, for instance.  There's a little
    carrier for the XMIT crystal with easy user access, as well as having
    the RCVR crystal jack-mounted right next to the power input line.). 
    
    Other stuff requires a Commercial license, and specialized equipment
    like a spectrum analyzer.
    
    Look at your owners manual to see what you're allowed; there should
    be a descriptive paragraph on how-to-do-it if you are allowed to
    do so.  Or call the radio manufacturer.
    
    Generally you can swap crystals only within a particular band (i.e.
    72.xxx for 72.yyy).  Going from 27 to 47 to 49 to 72 to whatever
    is either difficult or completely impossible.

    So, if I have a Futaba Conquest 4NL AM radio and want to change
    the frequency chip (from channel 56 to 44), I must have a Certified person perform
    the change ? 
    

>< Note 693.3 by AKOV11::KAUFMANN >
>                          -< Legally and Technically >-
>
>    So, if I have a Futaba Conquest 4NL AM radio and want to change
>    the frequency chip (from channel 56 to 44), I must have a Certified person perform
>    the change ? 
 
Right - that is why Futaba and Airtronics have Frequency modules on the
back.  Cause other parts have to be changed and/or adjusted along with
the crystal swap.

Do yourself a favor and send the radio to Futaba for a frequency change.
It cost $25.00 and you can pick a new low band freq (depending on what
model Futaba you have (I'm not sure they can change the conquest)) and 
get a gold (1991) sticker on the transmitter
at the same time.  In the near future you won't be able to run your
transmitter without some kind of silver or gold sticker on it.  

Warning - this don't make the receiver 1991 - worry about that in the
fall of 1990.

Call Futaba in California and they will give you the straight scoop over
the phone.  I called about mine a few weeks ago and had a repair and
frequency change.  They were fast and good and reasonable.

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

    Well, I dunno about fast, Futaba took two entire months(!) to do
    1/2 hour of work on my first frequency change, that and the cost
    have me wondering if I'll even do the second one...
    
    Willie

>< Note 693.5 by SNDCSL::SMITH "IEEE-696" >
>                     -< Ask them about leadtimes first... >-
>
>    Well, I dunno about fast, Futaba took two entire months(!) to do
>    1/2 hour of work on my first frequency change, that and the cost
>    have me wondering if I'll even do the second one...
>    
>    Willie

Mine was about a week.  I called them first of course.

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

    Futaba will tell you it is probably ok to go up one or down freq
    without retunning. Like from 56 to 54. Futaba is saying you can
    go as far as from 38 to 56 without tunning on the 5 channel Conquest
    PCM. Now all you need is some crystals. Get your local hobby shop
    to order some crystals for you. Approx. $18 for AM and $27 for FM
    is approx list price.
    
    Bob

    
    
    Thanks for the info - I'll call Futaba in sunny Ca. and see what
    they have to say, though it's awful tempting for an old radio hack
    like me to just swap crystals (IF I COULD FIND THE %*$& THINGS!).
    Better to do this legit, though, and get a sticker on the transmitter
    besides.  Sounds like something to do in the dead of winter, huh?
    
    Mark
    

>I currently own a Futaba Attack which is currently serving time in my 
>Eagle 2.  I have an Airtronics Vanguard PCM on order for my next 
>project.  I'm happy with the Attack.  Hope I'll be happier with the 
>Vanguard.  However, my question is based on an earilar reply.  Can 
>anyone tell me what the usual procedure is to change channels, on both 
>the Futaba stuff (particularly the Attack series) and the Airtronics 
>stuff.

That's easy - you have to send it back to an authorized repair facility.
In most cases the easiest thing to do is send it back to the manufacture.

Anything else is illegal (for the transmitter) and not ethical (for the
receiver).  The fact that the crystals plug in is of no benefit what
so ever.  In fact I wish they would not have them readily accessible for
two reasons.

1.  Uniformed people will change their own crystals and run radios that
    are not functioning at full capacity.

2.  They are very susceptible to moisture.  On these hot and hazy days
    if you can form some moisture on your receiver crystal your plane
    will go nuts.

Let me change the subject just a tad.  I don't use a neck strap.  Maybe
I should but I don't.  When launching sailplanes I have to hold the transmitter
with one hand.  I really appreciate good design on the human engineering
of the transmitter case.

Now about your attack and vanguard.  I had an attack for a week and sent
it back for the wrong reasons.  I have never since had any transmitter
that had such nice human engineering on the case as the Attack.  The side
grips are terrific.  The top of the line Futaba is not.  None of the Airtronics
come close either.  JRs are no good - BUT - I think the top of the line
JR - the 10 channel one - has nice grips.

Any other opinions on transmitter handles?
Anybody know of any transmitter enhancements for purposes similar to this.
For instance - I wouldn't mind putting a gob of RTV on a brand new Vision
transmitter if that is what it takes to make a good handle.

Sure wish I had some sort of a leather strap on my JR single stick so that
I could hold the transmitter with one hand.  Why can't I slip my hand
into something that feels like a catchers mitt and have a stick coming
out of it?

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

    
    	I have a question along these lines.....If trans./rec. crystals
    are changed I was told that the transmitter had to be "Fine Tuned"
    to the new frequency and that this could effect the range if not
    done.  Does anyone have any info on this ?
    
    Thanks,
    
    Andy Bernier
    SCOMAN::BERNIER
    

Both the transmitter and receiver utilize "tuned" circuits that
are adjusted for the frequency you are using. You can think of
it as a typical bell-shaped curve around a specific frequency.
The circuit works best at the frequency at the center of the
curve, and diminishes as the frequency gets farther away. Depending
on the circuit, it may have a wide or narrow curve (the variance,
or sigma, of the distribution). If the curve is wide it is less
sensitive to frequency changes, if it is narrow it is more sensitive.

Part of the design of the newer "narrow band" radios is precisely to
narrow the width of the curve, thus making the circuit very sensitive
to frequency changes. Some of the older wide band AM radios had little
effect if you changed crystals to a different channel. Some of the new
ones might not work at all without retuning. In fact, I believe some
radis have a module that you switch, instead of just the crystal, with
the module containing the tuned circuits that are adjusted for the
crystal.

I think it's reasonable to advise anybody with a "1991" radio set to
not change crystals without having the radio serviced and retuned, or
at least to contact the manufacturer for explicit instructions on
changing channels.

Dave

    
    I think it depends on the range of xtal frequencies and rx design.
    Most front end mixers can withstand small frequency changes with
    only marginal affects.
    
    The UK sets all have changeable xtals and have to agree to close
    specifications. I guess the slighly higher US frequencies would
    tend to make matters worse.
    
    Mark
    

    Does anyone know what the compatibility is between Rx crystals used for
    RCD rx and crystals used for Futaba rx (both FM)??  As mentined
    elsewhere, I need to change the freq of my recently acquired RCD rx.  I
    have a crystal  from a futaba Rx.  Can I just swap them??  If I try it,
    will I risk damaging the RCD??
    
    Is changing it from 22 to 40 going to require a re-tune??
    
    Thanks!
    jeff
    

    Jeff,
    
    	These is a local modeler that works for United Technologies that
    does crystal changes.  He a club member abd retunes the RX and TX
    to meet the narrow band requirements.  If you're interested I'll post
    his phone number.
    
    
    Tom

    Sure, it never hurts to post another phone number..
    
    cheers,
    jeff
    

    All the RCD Rxs come without crystals and the retailer adds the crystal
    at the point of sale. Retuning never hurts but just swapping with
    another RCD crystal will be as good as "new" (would have been)

    Are all crystals the same between venders?

    Heard at Tom's today.
    
    RCD is real short on crystals and has bought a bunch from Ace. They
    have no date as to when they'll get more back in stock. Must make
    selling Rxs difficult.