I'm pleased to report that we got Uwe's BPSK transmission
working, after some advice from Markus.
The problem was that a phase correcting feedback loop was
sampling the signal after the modulator, not before. It was
therefore doing quite a good job of undoing the phase shift
Uwe made another transmission on Sunday of 12 characters with 10
second symbols and this decoded very easily here in Todmorden,
range 762 km.
I didn't know that Uwe was going to transmit so was doing some
maintenance at the time. The receiver was switched off for
nearly 30 minutes of the 150 minute transmission, and the GPS
timing system wasn't restored to correct operation until after
the transmission ended. Over 60 minutes of the reception did
not have reliable timing.
Despite all the missing symbols, Uwe delivers such a strong
signal that the Eb/N0 averaged +2dB which made it a very easy
decode. Expectation based on carrier measurements was at
least +2.0 dB.
The S/N at the rx output was -74 dB in 2500 Hz.