Mic levels on FreeDV

classic Classic list List threaded Threaded
3 messages Options
Reply | Threaded
Open this post in threaded view
|

Mic levels on FreeDV

Graemej
Hello Jim and Group,

There is a big disparity between the audio level for best SSB operation and FreeDV operation. For SSB running the levels at -3 dB seems to give best audio but hopelessly overdrives FreeDV. Turning the mic level so the Peal Microphone Audio Level on the Config/TxAudio screen is at around -30dBm seems to be the best level i.e. 30 dB above my audio noise floor of -63 dB.

Is it possible to set audio levels so that the same mic level of -3dB is the correct level for both SSB and FreeDV so I can avoid having to set up each time I change modes?

I also notice that the RF level is much less than the Digital RF level which I run at 60% of full power. The digital modes are pretty close to this figure but FreeDV is only about half this.

Thanks for FreeDV Jim I am really enjoying it and David Rowe is following my activities on Quisk as I often work VK using this mode.

73, Graeme ZL2APV
Reply | Threaded
Open this post in threaded view
|

Re: Mic levels on FreeDV

ahlstromjc
Administrator
Hello Graeme,

The level of -3 dB you use for SSB should be fine for FreeDV too.  The mic processing increases the gain to get full amplitude of audio samples, for example, 2**15 -1 for 16-bit samples.  Then FreeDV or any other software should be prepared to accept full range samples.  I haven't used FreeDV for a while, but it used to work.  Please try listening to Tx audio with the Record feature while in FreeDV mode and see if the audio sounds OK.  Also, am I correct that you are using Linux and HiQSDR?

Jim
N2ADR
Reply | Threaded
Open this post in threaded view
|

Re: Mic levels on FreeDV

Graemej
Hello Jim,

Sorry yes it is Linux Mint 18.2 with HiQSDR. Confirming that at the receiving I get reports of overdriving the audio when using the normal level of -3 dB at the config/TX Audio with their trace severely thickened and furry on the graphic display. Reducing my audio to -30 dB cleans up the received audio with no loss of level at their end so it would appear to me that the level provided by Quisk to the codec is too high at the standard microphone level. This does seem to be a new development as I got very good audio reports initially and could have changed as much as 6 months ago. A variable on the initial reports is that I had a computer hardware failure and replaced it with a complete software rebuild 2 weeks ago.

Regarding issue 2 which is that the RF level from Quisk is less on FreeDV than other digital modes. This was the case from day 1 and there have been no changes.

I am not sure if any other users are using FreeDV but if so it would be helpful if they can confirm the same issues or not which would narrow the problem to Quisk or finger trouble at my end.

I know you are busy with filters etc. Jim so don't worry about rushing the fix as I can work around the problem and have not yet narrowed it down with absolute certainty to Quisk.

73, Graeme zl2apv