Conference vmszoo::rc

    Ken,
    	You should be able to run the futaba receiver with the Airtronics
    transmitter but it's possible that the channel functions will be
    different.  I have flown a Futaba receiver with an Airtronics
    transmitter with no problems.  As long as both systems are on frequency
    there should be good communication between them.  Maybe the channel
    differences made it appear like nothing was working.  The buggy control
    surfaces were caused by the receiver getting both signals
    assyncronously.  The receiver can's separate the channels properly
    under these conditions.  That's why you get shot down when someone else
    turns on on your frequency.  Neither transmitter will have any control
    when this happens.
    
    Charlie
    

    Charlie,
    	I didn't get any response from any stick movement from the
    Aritronics radio.  My Futaba was off at the time so I figured I
    would get some kind of reaction.  
    
    	I don't plan on flying with a mix of radion equipment, I was
    just experimenting.
    
    Ken

Well, thanks to a bout of sleeplessness last nite, I at least
have a theory.

>I have a FUTABA 6NLK AM radio on channel 42 (72.630mhz).  My brother
>has an AIRTRONICS 6 channel AM radion on 42.  When I turn on my
>radio and receiver, all things are normal (of course).

OK two radios functioning normally on channel 42.

>But when I turned on his radio (with antenna down) my control
>surfaces went buggy. 

And well they should; a classic case of being shot down...


>With the antenna up, the interference went away.

Here's where the party gets rough; what happened, I think is that
your receiver went into oscillation with the strong signal.  As
I've said elsewhere, the receiver is designed to work with a wide
range of signal strengths; this design parameter puts a very big
feedback loop from the detector to the first IF, which can break
into oscillation even with the best of design, which BTW Futaba
doesn't have.  You may even have had some measure of control, but
it was only because your antenna was so close. 

>When I turned my radio off, I couldn't take over with my
>brothers radio which is on the same freq.!!! 
     
The acid test of my theory would be that you couldn't take over
with your transmitter either.  The only way to stop the
oscillation is by turning off your receiver, then turning on
again.

On the other side of the coin, this does lead me to some puzzling
experiences I've had at the field.  I have a Futaba transmitter
and an Ace Silver Seven receiver.  They work perfectly together,
and I've had no trouble.  I also use my Tower micro system with
the Futaba, also with no trouble...If what I think is true, that
Sanwa, who makes Airtronics, also made the Tower system, it
implies that the Airtronics should be compatible also.

But sometimes at the field when I'm waiting for the pin, I'll
turn my radio on just to get a feel for what the other guy is
doing.   Surprisingly, most of the time this doesn't work, my
surfaces move randomly or not at all.  I can't explain this, but
I can say that the S7 is tuned, tweaked, and tumesced for the
Futaba; that could be an explaination.

The Futaba and Airtronics radios use the same Signetics chip set;
this chip set is optomized for the standard 1.5 millisecond
center, though I have reason to believe that Futaba's center is
closer to 1.4 milliseconds.  This would only lead to a difference
in servo travel, not to a glitch as you describe.

    re .3:  It is possible that the guy flying was using a different kind
    of modulation even though on the same frequency.  AM vs FM or PCM.
    Your AM receiver would then receive the carrier but not generate good
    pulses.
    
    Just a Guess