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[TowerTalk] KT34 & Shunt Feeding

To: "topband@contesting.com" <topband@contesting.com>
Subject: [TowerTalk] KT34 & Shunt Feeding
From: Phil - KB9CRY <kb9cry@comcast.net>
Date: Sun, 28 Mar 2004 08:23:56 -0600
List-post: <mailto:towertalk@contesting.com>
I've got to drop my KT34XA to upgrade the element to boom adapters (one of the original KLM version has become loose and will be upgraded with the DX Engr. type) and while it's down I want to perform other mods (it's already been upgraded with the M2 upgrades). Anyway, this antenna is on top of a 72 ft. Trylon self supporting tower, which two years ago, I began shunt feeding on 160M. That has worked like a champ but I'm concerned that the high voltages have been messing something up with the antenna. Since the last year or so, I've noticed that the antenna seems dead on 10 & 15M. I've verified it's an antenna problem by switching in the backup radio. Front to back and SWRs on those bands are still OK but it just doesn't hear well; everything seems attentuated. 20M seems OK. So, I have a few questions for the group:

1. The original KLM 4:1 balun is a voltage type, correct? I'd like to change this out to a current type. I know some folks who are using the Radio Works replacement with good success.
Can I make my own out of ferrite cores and using an impedance matching system (dual 50 & 75 ohm coax)?
Exactly what type & material cores should be used?
To what frequency is the matching system sized for since it's a multi band antenna?


2. Can my attentuation problem be caused by the high voltages of the shunt feed messing up the balun?
When I did my annual inpection up top last summer, I did not notice any damage to coax, the element to boom insulators, etc.


3. The KLM has elements which are insulated from the boom. I've read previously that one can place an impedance jumper (?) between the element and boom to prevent high voltage arcing at the insulators. Please tell me exactly what to do here.

Any other suggestion would be appreciated. Tnx in advance, Phil KB9CRY

_______________________________________________

See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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