I work PSK31 and to be honest I have never noticed drift to be a problem. The one respect in which I wonder whether the BFO stability mod may be some help is that I set my narrow CW filters up to be centered on 800Hz, same as the audio filter, and next time I use them they seem to have shifted the passband several tens of Hz one way or the other. -- Julian, G4ILO. (K2 #392) Homepage: http://www.qsl.net/g4ilo