Filter tested on analyzer

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From: John Welch (jjw@seastar.org)
Date: Mon Mar 14 1994 - 01:24:17 EST


        I put the filter on a spectrum analyzer and recorded some
numbers. As designed it was supposed to have 2.2kHz bandwidth and
0.1db of ripple. It's a 5-pole Chebychev, designed from the 1982
article in QST. I did no tuning, and used the closest standard value
capacitors to what was calculated. I did add the series caps
indicated in the article, to make the shape more closely match the
calculated values.
        Results are: 2.4kHz bandwidth, 4.8db ripple, at the lower
edge it falls off 25db in 600 hertz and at the upper edge it falls off
28.7db in 500 hertz. Insertion loss is 3db.
        It's not good enough to remove the unwanted sideband, but it's
not too bad all in all, for a 5-pole filter. The ripple is a little
high, but probably acceptable for home-built no-tune stuff. I imagine
I could get the ripple down and maybe the skirts improved by tuning
each section, but that's a bit more masochistic than I want to be for
a simple project. I might do it for my own 8-pole SSB filter, just to
see how hard it is (and how good it sounds).
        73 y'all, hope this inspires more building...

-- 
John Welch, N9JZW


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