Re: #audio #audio

Basil Gunn


Trying to understand differences between the two units you are

Things to try for more data points.
1. swap RPi SD cards
2. swap DRAWS hat

One unit has a power-down switch?

What radio (make, model) are you using?

You set the lowest level (PTM_P1) for the DAC PowerTune control (DAC
Playback PT) which drops the LO Drive output voltage down to 330mv
P-P. What happens if you use PTM_P2?

See comment below.

David Lowry <> writes:

An RPi3 plus an older draws hat is running with nwdr14 and adc gain
set to 0 dB. Audio knob from the radio is set to give an average level
of 50 in received direwolf packets.

An RPi4 plus the new draws hat with all else equal, I have to either
crank the audio knob up a quarter turn or leave it and adjust adc gain
to +7 dB in alsamixer to get the same average level 50 in direwolf.

Both sets of hardware were updated through piwiz and git pull on the
n7nix dir.

direwolf is decoding equally well in either case so this may be a
non-issue from a practical perspective. But should this be a concern?
If not, I’ll happily move on.

Thanks for any insight. I will not be able to respond with any
requested console output until this evening. There are some snd_card_*
differences between the boards from showudrc if that could be

BTW, thank you Basil for your scripts. My students studied fm side
band theory and ultimately used measure_deviate along with gnu radio
and rtf-sdr to put it into practice. The project was well received.
Thanks and happy to hear that you found the script useful. Appreciate
the feedback.
/Basil n7nix

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