RE: JR Radio help...any Techs out there?
A crystal circuit is pretty basic.. see below for a simplified oscillator. It consists of a bias voltage, the crystal (C0) and either a passive capacitive / inductive loop or a loop controlled amplifier. The simple C/L version is shown. The crystal only oscillates at its native, or harmonic frequency, and is coaxed "into oscillation" using the inductors and capacitors as shown below.
In a nutshell without going into why - it is very unlikely the crystal can "vary" with heat or energy changes within the circuit if it is in certifiable working order. It is however possible for feedback loop amplifiers and multipliers to vary if there is a defect or some other anomaly in the control circuit. This would cause a drift in the carrier or center frequency. JR would have done an extensive test on this however and if they found nothing it is very unlikely there is anything wrong with the circuit.
You have done everything anyone would have done. Here is what I would do first:
Foremost - check and double check ALL connections (make sure all extensions are heat shrunk and use Ernst safety clips on all removeable connections (i.e. ailerons). Make sure there is not as much as a pinhole or any kind of chafing on your ignition lead and that all of those connections are heat shrunk as well.
PUT IN A PPM (NOT PCM) receiver! Troubleshoot the problems with that using your TX and RX crystal set. With the PPM receiver in place - when the problem arises, start unplugging channels until the problem goes away.
My gut feeling says you have a problem at the RX , not at the TX. It could be genuine RF interference on your channel. You had indicated you "checked" the channel for interference, however those cheapo channel scanners are useless for crosstalk and spurious noise - they only monitor carrier frequency and not sidebands more than -3db. They are not fast enough to catch transient interference, the kind that could confuse a RX but not put it into failsafe. The only way you would ever detect that kind of interference is with a spectrum analyzer and chart recorder...(way expensive) ..
Interference more often than not, comes from a faulty device or connection on board, rather than over the air.
Using a PPM receiver will allow you to see the issues, without masking them away with failsafe.
You probably think you are chasing a ghost, trust me, you will find the issue. Since you said that someone else flies all day on the same freq I am going to lean away from true channel interference and lean more toward something on board. Some wierd things I have seen in the past you might want to check -
Carbon buildup inside engine (no, I'm not kidding, it can be a real RFI generator)
Cracked Spark Plug
Carbon Track on plug boot
Chafed through ignition lead(s)
Poor Ground on engine
Loose servo extension(s)
Antenna too close to metal objects or wires
Bad ignition module (RF leaks)
Noisy Regulator
Noisy / Failing Servo Amplifier (i.e. bad servo)
Many of these things develop and degrade over time!
Try the PPM route, run the tests with engine on and engine off and by unplugging channels. I am almost certain you will find your problem.
Anyway, hope this helps and let us know how you make out!
DP