[SEDXC] FW: Band Pass Filters

[AE4CW]

For Field Day this year we put together stub-based band rejection filters
that worked quite well.  We were looking for all the rejection we could get
for the least expense/work.  Based on the nice work in W2VJN's book on
Managing Interstation Interference we put together cascaded stubs that
rejected 40 and 15M while passing 20 and 10M.  Another set passed 40 and 15M
while rejecting 20 and 10M.  Both sets provided better than 40 dB of
rejection.  This is probably more than you need for QRP and a single stub
might work just fine as Tom indicates.  The cascaded versions are a bit
fussy to construct , and a VNA is almost a necessity to get them right, but
I think the single stubs could be done with a simple antenna analyzer.  In
any case, W2VJN's book is a good read.

---
Chuck, AE4CW 


-----Original Message-----
From: sedxc-bounces at contesting.com [mailto:sedxc-bounces at contesting.com] On
Behalf Of Tom W8JI
Sent: Monday, October 24, 2011 5:38 PM
To: Jack Nelson; sedxc at contesting.com
Subject: Re: [SEDXC] Band Pass Filters

> Now and then, I like to leave the 7600/9500/stacked StepIRs, and take 
> the popup and do a little QRP to the Field. I generally have someone 
> with me and we throw up a couple W3EDPs into some trees and try to 
> operate on two bands.

Radios have a lot to do with it. Filters really just make up for radio
shortfalls, no matter what radios we have.  What radios do you use? How far
apart are the antennas?

Depending on the radios, antenna spacing, and bands, even a little 1/4 wave
shorted stub on each radio might work.

73 Tom 

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