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Re: [TowerTalk] VHF/UHF Common Mode Choke

To: towertalk@contesting.com
Subject: Re: [TowerTalk] VHF/UHF Common Mode Choke
From: David Gilbert <xdavid@cis-broadband.com>
Date: Fri, 28 Jun 2019 19:28:28 -0700
List-post: <mailto:towertalk@contesting.com>

Can you please explain how a T-Match eliminates the need for a choke?  Fundamentally a T-Match itself is a balanced network, and unless you purposely unbalance it I don't see how it eliminates unwanted common-mode current.

And if you do purposely unbalance it in an attempt to eliminate unwanted common-mode current, how do you conveniently determine when you have done so?  You'd have to measure RF current on the outside of the shield at multiple points on the feedline while hoping you weren't contributing to detuning with your body.

Somebody smarter than me needs to explain all that before I buy it.

Dave   AB7E



On 6/28/2019 3:58 PM, Dave Sublette wrote:
Using a T-match eliminates the need for a choke, for the most part.  I have
T-matches on everything from 2M to 70 CM.

Dave, K4TO


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