Alex NS6Y wrote:
And #2, how well do audio filters, or even audio DSP like SGC sells, for
narrowing things down for listening to CW?
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IF, and that can be a big IF sometimes, all the signals getting through the
2.5kHz IF filter do not overload anything between the IF filter and an
added
audio filter, and the circuits between the two do not generate detectable
intermodulation products i.e.crud, the audio filter will help in two ways.
(1) Prevent you hearing the signals blocked by the filter. (2) Improve the
'sensitivity' of the receiver because its noise floor is reduced. How much
the noise floor is reduced depends in this case on the ratio IF Bandwidth /
Audio Filter bandwidth, so a 250Hz Audio filter should reduce the noise
floor by a factor of 10, or by 10dbm. This is an approximate but very close
figure, the actual amount depends on the 'shape' of the response of both
filters.
73,
Geoff
GM4ESD
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