To test the SDR (DVB-T dongle)
sudo apt install rtl-sdr
sudo systemctl stop piaware dump1090-fa
rtl_test -t
If SDR (dvbt dongle) is good, the last command above should give following output:
Found 1 device(s):
0: Realtek, RTL2832U, SN: 00000000
Using device 0: Generic RTL2832U
Found Rafael Micro R820T tuner
Supported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
[R82XX] PLL not locked!
Sampling at 2048000 S/s.
No E4000 tuner found, aborting