Re: LF: Linear amplifiers , MSK, and 500kHz

[DL4YHF@aol.com]

Greetings all,

I tried writing an MSK decoder, re-using parts of the PSK31/PSK08 decoder, but like Bill didn't get it working properly. Furthermore, at that time I was happy with the performance of PSK08 (and even PSK02) as implemented in Spectrum Lab - most of all because the maximum output power of my "almost-linear" PA was limited to 80 Watts so efficiency was not an issue (but this may change soon...).

To anyone trying an implementation of an MSK decoder: Forget the simple approaches using Squaring- and Costas Loops - it takes more than this. Producing an MSK signal, on the other hand, is simple if you treat it as frequency shift keying with a modulation index of 0.5 .  The bandwidth efficiency (if we had an optimum decoder) would be 1.9 (bit/sec per Hertz), almost the same as for QPSK. But, as so often, real-world problems seem to have prevented MSK being used as narrow-band amateur radio mode.

Best regards,
Wolf DL4YHF.