Experiments with Computer Assisted CW

I have been experimenting with computer Morse decode software, both with an aim of helping me on air and also for use in demonstration. I will be helping at a Scout camp in a week’s time and could set up an amateur station there.

This lunch time I experimented with CW Skimmer on Windows and XDeMorse on Linux. Both seemed to have potential. I tested CW Skimmer on air and XDeMorse using G4Fon.

I was pleased that I could hear the characters better than either program. My CW learning journey is coming on. I just need to turn this into recognising words reliably! Both programs have potential. CW Skimmer gave issues, but I’d like to try XDeMorse on air!

CW Skimmer

CW Skimmer was run on a Thinkpad laptop. Audio was fed from the KX3’s IQ output through an old Zoom H1 acting as USB interface. Sample rate was 48kS/s.

CW Skimmer copying a signal

CW skimmer was able to copy reasonably well. Where it failed, I was able to copy the missing characters and work out what was sent. Unfortunately I was not able to get either the IQ Audio option working (failed to load Object error) or the CAT control working. As soon as I connected the CAT cable I saw a lot of interference, whether through the Zoom or the CAT USB I don’t know?

Interference with CAT interface connected

I had great difficulty finding the signal that the radio was receiving in CW Skimmer’s display. Maybe I’d have been better using it in “3k Radio” mode so that it shows only the audio from the radio. It will take some work to understand how to use the interface to navigate the huge input bandwidth it is processing.


XDeMorse copying a signal from the G4Fon software

I experimented with XDeMorse on the old Acer Aspire One. This is an Intel Atom single core machine, now quite old. It runs Lubuntu and the TucNak logging program. I had to download and install XDeMorse latest from Debian because the version shipped with Lubuntu will not start.

Copy was impressive, even when signal strength and noise strength were set the same. The only things that really upset it were:

  • Enabling both Straight Key and Random Weighting at the same time.
  • Enabling the QRM function which mixes in a lot of random Morse background noise.

XDeMorse works with the receive audio from the radio, rather than the wide IQ signal. This does mean that making sure it is copying what the radio is listening to is easy. I’d use the KX3’s filters to isolate the sone signal of interest. I could also try it with the MTR3B which has a fixed filter.

CPU load was surprisingly low according to the top program, though the machine did start to become warm and battery life estimate dropped while it was running. I look forward to trying this program on air. The Aspire One is a lot more portable than the Thinkpad and a bit less nickable on Scout camp.

1 thought on “Experiments with Computer Assisted CW

  1. I wonder if part of the problem was that the KX3 receives on lower sideband. Although I’d told CW Skimmer the side tone frequency was 700Hz, I needed to tell it to look at -700Hz.

    I couldn’t work out what the control in the top right did.

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