A Guide to Working More DX by
Using Extremely Slow Morse

What is it all about?

Having been a CW enthusiast for 30 years, I pride myself on being able to dig very weak signals out of the noise. However, the technique described here allows perfect reception of signals which are completely inaudible!

First described by Peter Martinez, G3PLX, the technique involves using Digital Signal Processing (DSP) to integrate a stable carrier over several seconds (or even minutes) to give an effective bandwidth of a fraction of 1Hz. This can give your CW transmission the equivalent of a 20+dB power boost.

The result is displayed on a computer screen with a typical display bandwidth of a few tens of Hertz and shows Morse as lines which must be decoded by eye. The disadvantage is that it all takes a very long time with dots being between 2 and 10 seconds long.

Spectrogram

The system devised by G3PLX and developed between him and G4JNT is extremely effective but involved building a DSP board.

The breakthrough in the widespread use of this technique came when I discovered, thanks to an article in QST, a program called Spectrogram.

This was written by Richard Horne so that he could analyse bird song. However, one of its facilities used the same idea as the G3PLX program and - here's the good news - it required no external hardware and could be downloaded free from the Internet. The bad news was that it required a fast computer (fast 486 or a Pentium) and a Soundblaster compatible sound card. But if you have this kit already this is a really easy and cheap way to be able to work more DX.

This is the sort of display you get from Spectrogram. More can be found here.

Richard Horne has been intrigued by the use of his program for amateur radio use and has incorporated several facilities especially for us. He now has a special version just for LF enthusiasts.

Since the phrase 'extremely slow Morse' is a bit cumbersome, it is often abbreviated to QRSs (ie even slower than QRS).

Read Part 2: Getting Going