11 June 2009

CW vs PSK vs FeldHell

You might have read of my recent interest in machine generated modes (or "digital modes"). Lately I have filled my logbook with tens of PSK31/PSK63 contacts and one FeldHell. All on 30m with 2.5W power output into the horizontal base-loaded monopole antenna.

One night I could not get any contact in PSK31, so I got bored and moved to the CW part of 30m, where I collected 3 QSOs. All their sigs were 599 on my meter, including that UK HAM that was running 5W.

So, CW wins over MGMs? I did an Internet search and found references to a work of Tony K2MO (search it yourself). Besides his measurements, he published a minimum Signal-To-Noise ratio for error-free copy, where CW 20WPM scores -13dB, PSK31 -10dB, PSK63 and FeldHell -7dB.

The lower SNR, the more noise is accepted for error-free copy. So, CW@20wpm is more robust than PSK31. Given the 3dB difference, I need to double the power when doing PSK31 to obtain the same CW SNR. One more double for FeldHell.

So: CW 2.5W, PSK31 5W, FeldHell 10W.

In theory of course.