Muted Acknowledgements

My computer mutes received sound that immediately follows transmitted sound, specifically the AX.25 UA acknowledgement packet that’s received immediately after transmitting SABM or DISC. I can mitigate this by setting the receive audio level < 70%, in ‘Control Panel > All Control Panel Items > Sound > Recording > Digirig > Properties > Levels.’

I listened to the received audio by ticking ‘Sound > Recording > Digirig > Properties > Listen > Listen to this device.’ When the Level is set to 69%, I hear the audio ramp up from very quiet to full loudness as an acknowledgement is received. Direwolf can usually read this signal. But at higher Level settings, the muting is more pronounced and Direwolf doesn’t read the UA packet. At the same time, I hear the received packet at full loudness through the radio speaker.

I’m using Direwolf version 1.7 on Windows 11 Home on a cheap laptop (Chuwi HeroBook Pro). Windows is configured to treat the Digirig input and output as Default Communication Devices, and to Do nothing (in Sound > Communications) when it detects communication activity.

I see the same problem on Windows 8.1, although at a different Level of received audio. I don’t see this problem with a DRA-65 instead of a Digirig.

Can you recommend another way to prevent this problem? Decreasing the receive audio level works for me, but it might be impractical for others.

I did not want your question to go unanswered too long. Do you have Properties → Custom → AGC unset for the Digirig?

If it is unset and you have the problem you describe, your problem is too subtle for me!

73 Constrainted

Yes, AGC is unset (not ticked).

Thanks for getting back. My Digirigs’ ( 3 units) receive audio level is stable across fldigi, soundmodem, multipsk, and Vara FM. I have not used other USB soundcards, so I cannot compare.

I am evaluating the Digirig as a headset soundcard, and again, audio levels are stable.

Maybe someone else will comment.

73 Constrainted

@Kilo I should have mentioned the guide, Troubleshooting Digital Modes – digirig which can help you isolate each issue in turn.

73 Constrainted

Gosh that was my first thought too. This sounds like an aggressive AGC issue somewhere.

If AGC is turned to off or fast on your transceiver itself, does it behave differently?

My Icom IC-2730A transceiver has no AGC, as far as I know. Also, I don’t see the problem with a DRA-65 instead of a Digirig. Also, I hear the received packet at full loudness from the radio speaker, at the same time I hear the partially muted packet from the computer.

I see the same problem on Ubuntu 22.04.3 (using ALSA), although at a different level of received audio. So, I think the problem lies in the Digirig, not the computer.

I guess the different levels on different hosts result from differences in their mapping from percentage to Digirig’s level number. On Ubuntu, I see:

$ amixer -c 1 sset Mic 80%
Simple mixer control 'Mic',0
  Capabilities: pvolume pvolume-joined cvolume cvolume-joined pswitch pswitch-joined cswitch cswitch-joined
  Playback channels: Mono
  Capture channels: Mono
  Limits: Playback 0 - 127 Capture 0 - 16
  Mono: Playback 102 [80%] [19.12dB] [on] Capture 13 [81%] [19.34dB] [on]

I guess 70% on Windows 11 maps to the same Digirig level 102. I don’t know how to verify that.

I do not know amixer well, and I haven’t run linux in a while. Why does device mic (microphone) have playback settings at all?

73 Constrainted

They serve the same purpose as Windows’ control panel ‘Sound > Recording > device > Properties > Levels’. For example, if the microphone is too sensitive or it’s hearing very loud sound, this setting enables the user to reduce the sound to a manageable level. It’s useful for software modems, which may fail to read very loud received sound.

Do you have the receive audio level set to a high value (like 90% or 100%)?

For any of my Digirigs on Windows 11, Microphone USB is set to 0% for Vara FM, Vara HF, fldigi, multipsk and set to 20 for soundmodem. I hope that helps.

73 Constrainted

On my linux devices, I type:

Sudo alsamixer

Then I start off by selecting the digirig and setting everything to zero db and muting AGC. “MM” above ACG is mute. Then I exit and type:

Sudo alsactl store

Depending on what youre doing, you can come back to alsamixer and adjust levels later, but the alsamixer Auto Gain Control should remain off.