When I connect power to the servo plugs on APM to power the Rx/Servos the GPS Satcount goes to 0 nearly instantly. This is the case when using a battery for the servo rail, using an esc for the servo rail, and even when running the APM off a separate battery. (solder joint on APM board disconnected)
When servo rail is powered the servos act normally, the RX receives, switching into stabilized flight mode deflects the surfaces to restore equilibrium, but the GPS loses all satellites.
What other information should I give to help troubleshooting?
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To close this thread out, after replacing the Rx all the problems disappeared. I opened the original Rx and found many components missing/solder jumpers/components connected with only one pad. I tried to re-solder everything as best I could but cooked something. Thank you for your help Mike.
I had the same problem in my setup, had the gps on top of a FRSky rx.
Moved the gps to the rear of the aircraft(extended the supplied gps cable), problem gone.
Most consumer grade gps hardware has very little input filtering, and gps signals are such low level, that almost any "strong" rf signal swamps the input amplifier on the gps engine.
It not even need be near the gps frequency.
And almost all electronic devices give out some rf signals.
Sorry, running around today, I haven't had a chance to try your suggestions yet Mike, I did have a few minutes after I last posted when I found out:
Making a faraday cage from aluminum foil and placing it around the Rx and Rx antenna cleared up the problem. (and reduced the radio range to ~10 ft.) Powering up the Rx while not attached to the Ardupilot and bringing it near also causes the GPS to lose all satellites. Rx & antenna have to be ~8+ inches away for GPS to be unaffected. The reciever is a bit old and cheap, could a newer one make the difference or is it still likely a problem on the APM board?
After more investigation, it seems that the GPS loss happens when the Rx is connected. Still not sure of the root cause