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Re: [TowerTalk] Band Pass Filter Question

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Band Pass Filter Question
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Fri, 27 Nov 2020 14:31:15 -0800
List-post: <mailto:towertalk@contesting.com>
On 11/27/2020 2:00 PM, RVZ via TowerTalk wrote:
I realize it's best to install Band Pass Filters on both the transmitter and receiver.  But if only one or the other can be installed, can you tell me which of the two usually provides the best attenuation?

The most common bandpass filters are rated for 100-200W, PROVIDED that they are inserted at a point where they are inserted is well matched, for example between transceiver and tuner or transceiver and amp, so they will work on both TX and RX.

The major limitation of these filters is that they can't kill harmonics produced in a power amp -- that requires either stubs properly placed along the feedline or high power bandpass filters. Here's a survey I did my lab of the bandpass filters available to me in 2014. Near the end is a link to a page of links for individual measurements.

http://k9yc.com/BandpassFilterSurvey.pdf

This piece on stub placement also ran in NCJ. The second link is to slices for talks I gave at Visalia, Pacificon, and to several local clubs.
http://k9yc.com/LocatingStubs.pdf
http://k9yc.com/StubPlacement.pdf

73, Jim K9YC

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