07-07-2017, 09:28 PM
"The bar graph on WSJT-X sits as if there is audio there hovering between 40-60dB, but there is no input on the microphone (I've disconnected it). If I mute it from the audio controls (red button) then it disappears down to zero. "
Is the RX audio from the radio (via the interface) to the mic input on left, right or both inputs (mono) ??
Does the indicated level look random like white noise or more constant like hum pickup ?
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.
Other thoughts have to do with input impedance of the USB sound interface. Low or high ? Interface output impedance - high or low ?
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 ?
Apologies for all the questions but they might help shine the light in the right place.
73 Doug VK4ADC
Is the RX audio from the radio (via the interface) to the mic input on left, right or both inputs (mono) ??
Does the indicated level look random like white noise or more constant like hum pickup ?
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.
Other thoughts have to do with input impedance of the USB sound interface. Low or high ? Interface output impedance - high or low ?
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 ?
Apologies for all the questions but they might help shine the light in the right place.
73 Doug VK4ADC
Doug VK4ADC @ QG62LG51
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.