Re: Re: [amsat-bb] 2 m filters

[<nx7u@xxxxxxx>]

Piero,
I think the best way to homebrew such a VHF or UHF filter is to use helical resonators.  The nice thing about helical resonators is that you have a large amount of control on the physical size of the filter.
The DCI filters Stan mentions use them.
They are fairly straightforward to homebrew.  Easier-to-get references are:
June 1976 QST, p. 11
http://mywebpages.comcast.net/tonne/helical.html
->which has a very good program you can download that does all the mathematical work for you

A hard-to-find reference is:
Zverev, Handbook of Filter Design, chapter 9 (if I recall correctly).

Good Luck!

> 
> From: Stan <stan@capecod.com>
> Date: 2002/10/16 Wed AM 08:58:17 EDT
> To: Piero Calvi <pcalvi@yahoo.com>
> CC: amsat-bb@AMSAT.Org
> Subject: Re: [amsat-bb] 2 m filters
> 
> Hello Piero,
> 
> These are not home brew, but they work very well and are
> cost effective.
> 
> http://www.dci.ca
> 
> Very tight bandpass, and low insertion loss in band.
> 
> I use on 6M, 2M and 222 MHz
> 
> Stan, WA1ECF   FN41sr  Cape Cod
> 
> 
> 
> 
> Piero Calvi wrote:
> > 
> > I am looking for resources on the Web for homebuilding
> > a 144-146 passband filter (I suffer from bad
> > intermodulation from FM broadcast). Can anybody help?
> > Thanks and 73. Piero HB9DSU
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