The ripple increases when the source or load impedance is incorrect. There is usually a termination capcitance so a transformer often doesn't work by itself.
73,
John KD6OZH
----- Original Message ----- From: "William Leijenaar" pe1rah@yahoo.com To: amsat-bb@amsat.org Sent: Thursday, November 16, 2006 08:13 UTC 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 ripple.
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: http://www.icmfg.com/107mhzfilters.html
73 de PE1RAH William Leijenaar
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