WSPR on Rasbian - Raspberry Pi 3

[VK7HH]

Hi All,
So I've managed to install WSJT-X on a RPi3 running Raspbian Jessie.

Using a USB to serial adapter and a USB soundcard. I've managed to get audio coming out of the USB soundcard for transmitting, but having issues with the receive audio.

I've set the default to the USB soundcard and have only one capture device (USB). I've selected all the various options within WSJT-X, but none seem to be working.

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. 

I know my USB and audio interface are working from a Windows box. 

I can post screenshots if it helps. Am I missing something? I've checked in alsa configs that the sample rate is 48000Hz too. 

Anyone got any ideas?

[VK4ADC]

"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

[VK7HH]

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.

[VK7HH]

Fixed my issue...

For some reason the Pi didn't allow the soundcards left channel to operate, only right. I changed to a stereo plug with the right channel as my audio input.

There is still some inherent noise, so I switched off the radio and turned the volume down in WSPR-X until the reading was 0dB. I then switched the radio back on and adjusted the slider up to 30dB. It's been working fine and decoding stations on 10m over the weekend.

[VK4ADC]

Maybe I asked enough questions to make you contemplate the sound card connections 

[VK2ZIW]

I chose the Banana Pi as my "Pi of choice" because it has a SATA port and on that I have
a REAL SATA hard disk and on my other BPi, an SSD.

And for Linux flavour, Fedora is, by far the best with support for all types of ARM boards.
I've just built a BPi with a 2Tb disk and a Ubuntu linux 16.04. But, I can't upgrade the kernel.
And, it gave no way to support any other ARM boards. Also, I couldn't move the whole "root"
filesystem to the SATA disk.

Software
=======
I've had excellent success building MSHV for Meteor Scatter.
But WSJT-X is far too CPU hungry to run well.

I've been using the Banana Pi from it's early days, getting on three years now.
Yes I have a Raspberry Pi but only the 256Mb memory version. It's useless.
The SD cards wore out in days or weeks. That's why I say, "SATA disk or forget it".

As a super-low power Linux system with reasonable webserver performance, it can't be beaten.

For MMDVM, the Banana Pi, 128Gb SSD and Arduino DUE, total current drain 0.55A at 5V.
That's 2.5W!!

Alan VK2ZIW