[amsat-bb] Re: Help with crystal filter
kc6uqh at cox.net
Thu Nov 16 22:34:22 PST 2006
Suggest a FET follower, dual gate type, and a resistive 5 k load.
----- Original Message -----
From: "William Leijenaar" <pe1rah at yahoo.com>
To: <amsat-bb at amsat.org>
Sent: Thursday, November 16, 2006 12:13 AM
Subject: [amsat-bb] Help with crystal filter
> Hi AMSATs,
> For a (small) transponder design I am checking
> different kinds of filters. I need something small and
> cheap, and I tested some of the monolitical 10M30A
> crystal filters.
> The problem is that I can not get the ripple less than
> 2dB, where the specs say 0.5dB. I can see the 2 poles
> with a kind of bath-tube in the middle. I think the
> problem is the matching of the 5000 ohm impedance in
> the specs.
> In my design I used small 5mm transformers, that
> doesn't work at all. More tests with a "pigs nose"
> transformers work better, only not better than 2dB
> Maybe someone has experience with these monolitical
> crystal filters (especially the wideband 10M30A) ??
> I wonder how sensitive these filters are to an
> impedance miss-match, and how to get the optimum out
> of these filters ??
> Specs can E.g be found here:
> 73 de PE1RAH
> William Leijenaar
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