TopBand: RF analyser

[Peter Chadwick]

>The only problem with filters is that they usually need something close
to
>their design termination impedance to have their frequency-responses
stay
>as-designed.  A highly reactive load or one with an impedance far away
>from the filter's expectations will upset it greatly.  

The mismatch has more effect on the passband than on the stopband -
usually gives horrendous ripples in the passband with increased loss as
the mismatch gets worse. However, really mismatching a crystal filter
can give a Gaussian top for about the first 6dB, stopping ringing. But
you then end up with about 20dB of insertion loss.

73

Peter G3RZP
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