Quoting Roy Dean via AMSAT-BB who wrote on Sun 2020-10-11 at 11:52:
Does anybody have experience with this combination? I've been having issues with my dedicated FoxTelem Raspberry Pi station, so I've taken it down in favor of my APRS SatGate (which uses an RTL-SDR instead of the FCDPP) - and decided to use the FCDPP for my Rx in my normal everyday shack operations. However I can't seem to connect to the dongle at all with GQRX. GQRX is doing something, but there is no waterfall and no audio.
I'm somewhat concerned that the issue with my FoxTelem station was with the dongle itself, as I seem to remember successfully connecting to the dongle with GQRX in the past. I've tried the dongle on two separate pcs running Ubuntu 18.04 with no luck.
The sampling part of the funcube dongle is an audio device from the view of Linux. This means the audio subsystem will 'grab' it and make it available to applications.
Run (may need to be installed) pavucontrol, go to the Configuration tab, find the funcube dongle that will show as 'FUNcuble Dongle' there and switch the 'Profile' to 'Off'.
Now try again with qgrx.
Changes you make with pavucontrol are saved automatically.
Koos PE4KH