Can't get RTK injection to work on Solo

I have the XXL base and a Solo RTK GPS. This was a new Solo. I took it out of the box, flew it once, then took out the Rev B GPS and replaced it with Drotek. I’ve updated the firmware, rebooted and saw the party lights. Went outside to a convenient location (call it A) connected to XXL using Mission Planner, clicked M8P autoconfig and M8P fw 130+, waited 10 minutes for valid signal at which point the Base, Glonass and GPS lights were all green, I went to Flight Data tab and saw the 3D dgps indicator and then I flew it. Seemed to work OK.
Next day I took it to a new location (call it B). Opened MP waited 10 minutes to get the new valid base coordinates, but this time the Solo could not get a GPS fix. After 2 hours of trying everything I could think of, I gave up.
Next day I went back to location A. Waited for a valid GPS base fix, but it kept showing location B in the map. Again I could not get GPS fix on Solo. Disconnecting the base from MP still no GPS fix and 0 satellites. I noticed that if I covered the GPS antenna on the Solo the satellite count went up to 7 or 8. Then if I took my had away it quickly went back to zero.
What can I be doing wrong?

Strange. Sounds like an issue with EMI noise.

Check the following:

  • latest ublox firmware installed on rover and base? (should be 1.3)

  • check the shielding and wiring of the gps in Solo. Best is to have the 3DR V2 shield installed. Also, the ferrite ring on the gps cable is mandatory.

XXL and Solo RTK Firmware:
Software version:
EXT CORE 3.01 (d080e3)
ROM BASE 2.01 (75331)

The ferrite ring is in place. I was using the OEM copper GPS shield, but I have the V2 shield and will try it. I am skeptical that this will make a difference.

The Mission Planner version is 1.3.48 and it looks different than what is shown in Drotek web site. I had to click on and M8P autoconfig and M8P fw 130+ to get the SurveyIn and Time settings. Is this correct?

I have rechecked all of the settings on XXL, installed the V2 shield, and visually inspected the installation. The XXL seems to work OK in U-Center and in Mission Planner RTK injection, but the Solo RTK GPS never finds any satellites (0) unless I cover it with my hand and then it goes up to 7 to 11 satellites but does not achieve a GPS lock. Also, when I disconnect the XXL and even if I shut down Mission Planner the Solo still does not acquire any satellites. I believe the expected behavior should be that the Solo should still acquire satellites but not get the 3D dgps fix. I have swapped back to the OEM Rev B GPS and all works fine. It seems like this Drotek RTK GPS may be faulty.