The following chart shows the Quadrature Sampling Detector roll-off over the narrower
range 0 to 5kHz. You can see that at the CW operating frequency 700Hz, the attenuation is
insignificant; the roll-off of the QSD does not significantly improve the selectivity of the CW
filter, but it does improve the intermodulation characteristics of the receiver.
6.9 CW Filter response
This chart shows the measured response of the CW filter (combined with the other filtering
in the receiver chain). It was measured by tuning the receiver across a test signal. Note that
the center frequency, a little over 700Hz, could be altered by changing some component
values.
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