[amsat-bb] Re: Help with crystal filter

James Duffey JamesDuffey at comcast.net
Thu Nov 16 17:19:54 PST 2006

William - I have not used these filters, but you may want to contact  
ICM directly for help. I think many of the engineers there are hams and  
you may be able to get some help by sending an e-mail to them.

You might also try matching into the ends with a L or pi network. Also,  
measuring the response with a 5kOhm resistor termination should tell  
you whether or not the problem is improper termination. - Duffey
On Nov 16, 2006, at 1:13 AM, William Leijenaar wrote:


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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James Duffey KK6MC/5
Cedar Crest NM 87008

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