Dear LF Group,
I looked at the Droitwich signal using Spectrum Lab last night - the phase
modulated signal occupies a BW of about 80Hz centered on the carrier -
however, measuring the carrier level in 100Hz Bandwidth instead of 25Hz
made no difference to the fluctuations in carrier level, so that blew my
theory of yesterday out of the water...
However, I tried another experiment comparing the carrier level (from the
SPM-19 with 25Hz BW) with the demodulated audio from a separate receiver.
The attached jpeg shows that the carrier level (top trace) really does go
down as the modulation (bottom trace) increases, as discussed by others.
The variation is about 2-3dB between silence and full modulation.
So now the mystery is - why does G4JNT's W-J receiver show a constant level?
Cheers, Jim Moritz
73 de M0BMU 
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