APM2 GPS more prone to RFI?

Perhaps its just that now the GPS is onboard, its closer to the other electronics on my jDrones hexa - but I'm suffering with an inability to get a 3D fix on the GPS.

My previous setup had the radio RX (JR RG831B DMSS receiver) and its telemetry unit (RA01T) on the lower carrier plate, the APM1 on the top plate, and the GPS receiver on the top of the dome on a standard jDrones hexacopter. This worked fine, GPS always got lock and seemed pretty stable.

Moving to the APM2, I've still got the radio RX on the lower plate, and now the APM2 above it. However, if the RX is powered, then the GPS won't lock - it occasionally acquires 1 or 2 satellites but never makes it further.

I've tried to isolate it somewhat - powered the 2 devices separately (APM2 from USB, RX from a lipo+BEC) and removed all the interlinks - still see the same problem. I've covered the top plate with foil, then place the APM2 onto foam on the foil - and it was better until I hooked up the PWM connections. I've removed the RA01T telemetry TX and that makes no difference.

If I place the APM2 alongside the RX, its fine. ie. if I remove the top plate and place it alongside the bottom plate on my work bench - then indoors I see 5 or 6 satellites and get a 3D fix.

Is this just a 'noisy' DMSS receiver? Is anyone else seeing this? Is there a recommended layout of the electronics that I've missed?



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  • I have the same issue, even with no RX onboard, only 6 ESCs (Hobbywing Skywalker 20A) each min. 2" away from the APM2. As soon as I connect my ESCs I have no Lock. I am trying and searching for weeks. Some day it is working quite good, but only for one day.

  • Did anyone with this issue ever find a way to resolve it?  I haven't isolated the problem to my receiver yet, but once I get a chance I'll try to.  I do get a lock when powered by USB indoors in a room with windows in about 5min.  Outdoors, and powered by lipo, I'm the same as you guys: 1 sat, then 2 sats, then 1 sat, then 2 sats, then 0 sats.  Every once in a while, I'll get to 3, but only for a moment. Occasionally, I have gotten a lock outside during a flight, but it is very rare.  Would LOVE to get this issue fixed.

    Anyone got a fix?

  • I don't like the position of the GPS. You want it to be on a high point of a plane, with many planes this will

    be difficult. Also any attached cables sprout like a forest around it, providing a screen for a chunk of the sky.

    I'll be using my old GPS on a ribbon cable. It did not get too great reception with the stock cable it came with, but when I got an extended cable and placed it right on the top of the airframe, it was great. I can't do that with this board :(

  • If there is adjacent interference it can affect a receiver. Placing a possible interfering transmission away a few inches can help much.

    The rule is inverse distance square from seeing light or RF. Unless focused.

  • I've had a variety of receivers in the stack above my APM2 board and it does not seem to have affected getting GPS lock, although it varies hugely in the time it takes to lock.

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