> It seems the 
> 198kHz carrier has some kind of cyclical drift in phase which occurs over a 
> period of a minute or two

Actually, for your communication purposes, do you need a stable frequency?

If Tx and Rx both lock to BBC Radio 4 or MSF or whatever, it doesn't matter if 
it drifts. Both amateur Tx and Rx drift together, so you can still have a very 
narrow-band filter.

You could call it LOWFUSS - LOW Frequency Unintended Spread Spectrum ;-)


73,
Chris G4OKW

-----------------------
Dr Chris Trayner
School of Electronic & Electrical Engineering,
The University of Leeds,
Leeds LS2 9JT, United Kingdom
Tel: +44 113 34 32053
Fax: +44 113 34 32032