This is just a quick How-To post about something I discovered today thanks to @bugobliterator.
If you ever find yourself wondering if your GPS is being affected by external EMI (as my aerial photography copter is) UBlox’s U-center has a “MON”, “SPAN” message that acts as a spectrum analyser. Once you know how to do it, it’s not too hard to get working although if you’re using a DroneCAN GPS it requires setting up serial-over-dronecan which requires the Python DroneCAN GUI tool to (setup is here Passing Serial over DroneCAN — Copter documentation)
For me I find when I power on my custom carrier board, little spikes appear which probably explains why its GPS signal quality is unreliable.
Of course this is not a good as getting a proper spectrum analyser like the Tektronic RSA306 or the more budget friendly RF Explorer but it’s simple and free.
For here3/4’s and possibly other dronecan GPS, you could try this workflow from mission planner to get the passthrough set up. Ignore the part about updating the firmware, this should get you connected to U-Center through mission planner
If you have a serial gps, this will do the same thing, open a tcp listen socket on port 500 for you to connect. MAVlinks supports serial passthrough at the protocol level for any device, but this button defaults to passing the gps serial port.
Tridge and Huibean have given me some additional information to handle situations where the vehicle is not available via a USB cable (e.g. the vehicle is in a remote location or has no USB port) and only available via UDP and you know its IP address
To connect using the python DroneCanGUI Tool where the vehicle is at a known IP address, set the “Select CAN interface” field to the IP:port of the vehicle and press OK
