Andy et all:

Initially I'll try the transmission on 138.83  (DCF139 ??) which hopefully
uses coherent FSK so the mark tone always returns to the same phase after
its burst of data

Bill de Carle, VE2IQ made some recordings of DCF39 some time ago and he
found the signal was breaking up on phase shifts continuously.  It will be
interesting to find out if they are phase stable on your side of the
Atlantic.

Larry
VA3LK