Wednesday, July 27, 2022

QDX with Fldigi on Ubuntu 22.04

The QDX works brilliantly with WSJT-X but I have struggled to get it working with Fldigi on Linux.

I'm pleased to report that I just had an Olivia 8/250 contact over a distance of 732km with VK2BLQ using Fldigi on Ubuntu 22.04.

Thanks to KJ7LVZ for the tip to install Pulse Audio Volume Control (from the Ubuntu App Store). That let me adjust and monitor send and receive audio levels.

In Fldigi I set the audio devices both to "pulse".

In the QDX settings I set the audio cycles to 1 (down from 480) as suggested by G3SPL. The larger number of samples is fine for slow changing modes like WSPR or FT8 but not good for fast modes like Olivia. Also I increased the receive gain to 75, up from 60 (I think), so I could see something on the waterfall in Fldigi.

Here's the Pulse Audio Volume Control window:

While I'm here, I've been using `screen /dev/ttyACM0` to configure the QDX but it's difficult to send ^Q as that's used for XON/XOFF. The trick is to type ^AQ. Hans, it might be good if there was another key to exit a menu than ^Q as I think many serial terminals might use ^Q for flow control.

1 comment:

Unknown said...

Hi Peter,

As you said in this post, the screen app uses ctrl-s/ctrl-q by default, so it swallows ctrl-q which you need for the QDX. You can use the -fn param to turn off flow control, which allows you to use ctrl-q as expected by the QDX. Try:
screen -fn /dev/ttyACM0