GMSK block, again

I’m playing with the GMSK demodulator block.

I have a signal at 24KHz, which I down-shift to DC, using a
freq_xlating_fir_filter. The signal is 200baud
MSK, so the filter bandwidth I set to 400Hz, then into the GMSK block,
arranging for there to
be two samples per symbol. This seems to be producing a nice stream
of 1s and 0s at 200bps.

Since the bits are encrypted coming from the source, I have no way of
knowing whether they’re the
“right” bits or not, so I want to confirm that my setup is correct for
the GMSK block. I think it
needs basebanded data, with the input spectrum arranged around DC, and
by default, it uses
2 samples per symbol.

Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium