>This means they will almost always modify all readings
>substantially near the cutoff or stop frequencies. A filter
>that rejects the AM BCB will have a major effect on 160
>meters.
I was thnking more along the lines of a simple quarter wave open coaxial
stub as a filter or a simple
three pole Butterworth used in the center of the passband, not at the
edges. A few percent freq shift from the passband center should not vary
much from 50 ohms. Yes it will have an effect but it would also be
measureable (phase angle, loss, etc.) and a controlled variable. One
should be able to compensate for those effects and adjust the analyzer
readings accordingly. This assumes enough out of band filter rejection to
allow the analyzer to hear its own reflection versus all the other RFI in
the neighborhood. If someone was only looking for 10 or 20 db of "nearby"
out of band rejection, it might be worth investigating. My nearest local
strong emitter is 400 KHz away from 1.8MHz, so my situation is not as
adverse as others might have. Mike WA3TTS
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