"You should have connecred Rx from radio to Tx on EB and vice versa.
If you're upgrading ground module's firmware - you have also to connect air module to PC and upgrade it's firmware to the same version. And also check if both modules have the same…"

"Try to swap two black wires next to red one.
But first check baudrate."

"Try to swap Rx-Tx lines, check baudrate (57k)."

"Rob, first check uCenter with direct connection to GPS unit, if this will sufficient for you. Than you can use radio link to connect this unit remotely."

"I've tested it before, both with NMEA and proprietary uBlox binary protocol - all works fine if you'll set correct baud for radio link.
But the question was asked over a half year ago and I'm not sure if is still valid..."

"Simple but worth considering :-)
PS. Pls, "Martin", not "Marvin" ;-)"

"He can connect i.e. M8N GPS receiver via radio link to PC running uCenter and control position from ground."

"Well, EN website version highly recommended..."

"1. This category is for 3DR Radio (telemetry), not for Pixhawk.2. There's no "geniune" or "fake" PIXHAWK - it's open hardware: https://pixhawk.org/"

"I'm afraid that at least one of them is dameged."

"For the test phase:
- TxPower=20,
- ECC on
- Min freq 414000
- Max freq 454000
- # of Chan 20-30
- Duty cycle 100%

Try this (with antenna attached ONLY - high Tx power)"

"Yep, I know, that was a little piece of advertisement for good quality stuff ;-)"

"NET ID has default value and you're using to much channels (max is 20-30 for stable work).
But IMHO this is not the root for your problem. If you're able - check your pair with different modem to find defective."

"Show me you radio config (screen capture)."

"No, connect ground module to PC as usual. Then power up air module with APM unconnected and Rx-Tx shorted, so radiolink should loop your transmission."