For a lot of us (I have seen this discussed before) the 3 db points
are fairly useless as a real predictor of performance. The 6 and 60 db
points do a much better job, telling where the skirts start, and where
they are diving.
I will never forget my disappointment in the Collins 500 kHz CW
mechanical filter (3 db) for my MP. I just assumed.....
Best thing is to get a sweep of the passband. Funny how those are so
hard to get for filters unless you're getting them from INRAD's
webpage. They have the Collins curves as well. You can compare curves
and see yourself. Interesting browsing.
You can see from the curves whether the skirts are still going strong
and diving past 60 db or whether they're dying and on the way to
having a poor ultimate rejection.
73, Guy
----- Original Message -----
From: "W3FPR - Don Wilhelm" <[EMAIL PROTECTED]>
To: "Bob Tellefsen" <[EMAIL PROTECTED]>; "Deni"
<[EMAIL PROTECTED]>; <elecraft@mailman.qth.net>
Sent: Saturday, November 13, 2004 1:18 PM
Subject: Re: [Elecraft] Talking filter Bandwidths
Bob and all,
The proper point is the 'halfway' point - half the power is -3 dB
(10 log 0.5) but half the voltage is -6 dB (20 log 0.5).
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