Amateur Radio Digial Mode FT-8 Decoding (RX Only – Receive Only) Using My Homebrew LMR SDR 1.1!

| August 12, 2026 | Amateur Radio (Ham Radio) | No Comments

Live stream here: https://www.youtube.com/live/e-oxuh7dJwI

Amateur Radio Digial Mode FT-8 Decoding (RX Only – Receive Only) Using LMR SDR 1.1! Using VB-Audio Virtual Cable (free download) to send FT-8 audio received in LMR SDR 1.1 to WSJT-X (free download). Configuration was quite simple, thanks to Gemini! Enjoy the wonderful continous decoding in 15m band. Using full wave 40m loop antenna. Planning to try RX on other bands later. Did not need time Sync software installation in Windows 10. Checking FT-8 signals on each band helps us to know which band is open to which region in real time. It is quite useful to see change in propagation from our region over a period of time. Enabled PSK Reporter spotting so that those transmitting will be able to know that their signals are reaching this location, though I will not be calling them back! But they can know the signal report from my setup automatically uploaded to PSK reporter.

Configuration Procedure

Here is the streamlined, receive-only setup:

  1. Send Audio from PowerSDR: Routing the receiver audio to the virtual cable.
    Open PowerSDR and configure the Virtual Audio Cable (VAC) to pipe the received audio out to Windows.
  2. Go to Setup > Audio > VAC.
  3. Check the Enable VAC box.
  4. In the Output dropdown, select CABLE Input (VB-Audio Virtual Cable).
  5. On the main PowerSDR interface, set your operating mode to DIGU (Digital Upper Sideband).
  6. Set your filter bandwidth to 3.0 kHz or wider so you don’t cut off any FT8 signals at the edges of the passband. Choose USB mode.
  7. Receive Audio in WSJT-X: Setting up the decoder.
    Open WSJT-X and tell it to listen to the virtual cable, bypassing any radio control commands.
  8. Go to File > Settings > Radio.
  9. Set the Rig dropdown to None.
  10. Switch to the Audio tab.
  11. In the Input dropdown, select CABLE Output (VB-Audio Virtual Cable). (You can leave the Output blank or set it to your default speakers, as you won’t be transmitting).
  12. Click OK.
  13. Tune and Adjust Levels: Optimizing for maximum decodes.
    Because WSJT-X isn’t controlling the radio, you will manually tune PowerSDR to the standard FT8 frequencies (for example, 14.074 MHz for the 20m band). All you have to do is type in the frequency by selecting VFO-A.
  14. Tune PowerSDR to an FT8 frequency. You should hear the signals (or see them on the PowerSDR waterfall).
  15. In WSJT-X, use the band dropdown menu (above the frequency display) to select the band you are listening to. This doesn’t change the radio, but it ensures WSJT-X records the correct band for its internal display.
  16. Look at the vertical audio level meter on the bottom left of WSJT-X. Adjust the main AF Gain (volume) in PowerSDR until that meter reads in the green, ideally between 60 dB and 70 dB on an empty part of the waterfall. Alternate option is to reduce VAC1 gain to about -8 or -12 dB. That will vary on each band. If signal is in red instead of green, audio clipping may occur, deterring good decode.

Once the audio level is set and your computer clock is synced to the exact second, the WSJT-X waterfall will populate and decodes will appear every 15 seconds. I did not install any synchronization software. Somehow, my Windows 10 seems to be synchronizing the clock well using my WiFi high speed internet.