Pichawk 3DR GPS lock issue. Powered by USB gets instant lock, powered by battery never locks

I have a GPS Lock issue.

I have a Pixhawk and 3DR GPS/Compass. Also have power module. I get almost instant GPS lock when I power the Pixhawk through USB cable. However, when I power off battery, I can't get a lock. The workaround I found is to first get a lock from USB, then plug in the battery...

Anyone else have this issue? Can anyone help point me in the right direction re: potential causes / fixes?

I tested pixhawk voltage out with a voltmeter and I get 4.8v from USB and 5.2v from battery. I put aluminum foil on the bottom the the 3DR Compass/GPS Module. GPS/Compass sits on a 6-inch mount.


  • Tarot 680pro
  • Multistar 4006-720KV
  • Turnigy Plush ESC (40a)
  • 3DR Compass / GPS
  • 3DR Telemetry
  • 5.8ghz Fatshark 600mw vTx
  • ***3 channel video switch *** (plugged into RC 10);
  • minimosd (3DR)
  • 2 4S 8000 Multistar Batteries in parallel
  • Feiyu Tech 3-axis Gimbal
  • GoPro


  • Running 3.3.1
  • ACC Calibrated
  • Compass Calibrated
  • Radio Calibrated
  • Compass Mot performed
  • Props and Motors on correctly
  • Autotune (Pitch/Roll)
  • ESCs calibrated, 1 ESC has the power wire which is plugged into the servo rail for back-up power. All others have ground and signal wires
  • ESCs mounted under the motors on the arms.
  • Rx mounted on the arm away from telemetry
  • I am powering the 3-channel video switch off the servo rail
  • I am powering the gimbal using a 12v BEC (split off before the power module)
  • I am powering the vTx off off a separate battery and running it through a LC filter (1A 3S)
  • I also made shielded cable for all of my FPV cables (vtx to osd, gopro to 3-channel switch, FPV camera to 3-channel switch)
  • low vibrations

Thanks for everyone's help.

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