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[TowerTalk] VHF/UHF Common Mode Choke

To: Towertalk <towertalk@contesting.com>
Subject: [TowerTalk] VHF/UHF Common Mode Choke
From: David Gilbert <xdavid@cis-broadband.com>
Date: Fri, 28 Jun 2019 11:50:19 -0700
List-post: <mailto:towertalk@contesting.com>

I've never been much interested in VHF/UHF, but with the current level of solar flux and the summer static I'm thinking of giving it a try using homebrew antennas based upon DK7ZB designs.  For 6m I'll probably use a coaxial sleeve as a common mode choke (unless somebody can suggest something better/simpler), but for 2m/70cm I'm planning to build a dual band yagi with a common feedline and I'm not sure a sleeve would work.  I guess it might, since 1/4 wave and 3/4 wave (432/144 = 3.00) accomplish pretty much the same thing, but I'd like some input from VHF/UHF hams who would know better than I.

And if a sleeve balun is indeed the way to go, what is the best way to fabricate one at UHF?  As W8JI points out, coax jackets aren't necessarily a low loss dielectric at UHF.

Thanks much for any suggestions.

73,
Dave   AB7E

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