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AO40.XLS and Receiver Bandwidth


I was playing with the AO40 Spreadsheet, and I noticed that the
Beacon S/N value is affected by the choice of receiver bandwidth.
This would make sense if you wanted to compare the signal level with
the total noise level, but that's not really what we want to do, right?
For the beacon, shouldn't the true receive bandwidth be determined not by
the receiver bandwidth, but by the bandwidth of the filters
in the demodulator (either hardware or DSP-based)?

I guess that the effective bandwidth of a 400-baud PSK demodulator is 1kHz
or so.  If you replace the 2500 Hz default value in the spreadsheet
with 1000 Hz, you get almost a 3 dB change in beacon S/N!

I noticed that if I switch my receiver from its 3 kHz to its 6 filter,
the quality of by beacon reception is not affected.  Also when I
switch filters, the spectrum display in AO40rcv does not show a change
in the SNR of the beacon itself;it simply shows more or less noise at
frequencies outside of the range of the beacon's bandwidth.


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