07-07-2017, 09:58 PM
Thanks Doug,
Try to answer below in bold.....
Is the RX audio from the radio (via the interface) to the mic input on left, right or both inputs (mono) ??
Set to mono at present.
Does the indicated level look random like white noise or more constant like hum pickup ?
It's pretty constant. With no input on the microphone input the WSJT-X level still hovers. Tested two USB soundcards, both the same. On my Windows box, it may sit around 2-5dB (i.e. no input)
Is there a gain step setting available under Rasbian like there is under Windows - which allows extra gain (eg in 10dB steps) above and beyond the normal mixer slider control value ? I know my cheapex external USB sound interface has this option under Windows so it may just be that it is preset up around +30dB or so by default on yours too.
The stated level and action as above are with the "capture" microphone gain all the way down to 1. I can adjust this level and see the bar graph move up in WSJT-X.
Other thoughts have to do with input impedance of the USB sound interface. Low or high ? Interface output impedance - high or low ?
Using the same USB sound card as I was using successfully through Windows. Input impedance would be low I think, they drive pretty hard. They go into 500K pots on my interface from memory.
Test for you to conduct: What level does the WSJT software display with the USB sound device input(s) individually short-circuited to audio signal ground ? Right channel grounded ? Left channel grounded ? Both grounded ?
I'll test this and see. It should be zero.
Try to answer below in bold.....
Is the RX audio from the radio (via the interface) to the mic input on left, right or both inputs (mono) ??
Set to mono at present.
Does the indicated level look random like white noise or more constant like hum pickup ?
It's pretty constant. With no input on the microphone input the WSJT-X level still hovers. Tested two USB soundcards, both the same. On my Windows box, it may sit around 2-5dB (i.e. no input)
Is there a gain step setting available under Rasbian like there is under Windows - which allows extra gain (eg in 10dB steps) above and beyond the normal mixer slider control value ? I know my cheapex external USB sound interface has this option under Windows so it may just be that it is preset up around +30dB or so by default on yours too.
The stated level and action as above are with the "capture" microphone gain all the way down to 1. I can adjust this level and see the bar graph move up in WSJT-X.
Other thoughts have to do with input impedance of the USB sound interface. Low or high ? Interface output impedance - high or low ?
Using the same USB sound card as I was using successfully through Windows. Input impedance would be low I think, they drive pretty hard. They go into 500K pots on my interface from memory.
Test for you to conduct: What level does the WSJT software display with the USB sound device input(s) individually short-circuited to audio signal ground ? Right channel grounded ? Left channel grounded ? Both grounded ?
I'll test this and see. It should be zero.