[TowerTalk] Balun design

n8ug@juno.com n8ug@juno.com
Thu, 15 Jul 1999 09:01:38 -0400


Hi Brian
What you have described is indeed a 1:1 "balun", in that it, as a choke,
imparts a high impedance to "3rd path" Rf current on the outside of the
feedline. It is not as efficient, however, as the W2DU type, introduced
by Walt Maxwell in the early 80's, which consists of 50 beads on the same
type of teflon coax and has enjoyed proven success for years.
As Walt suggested at one time, a choke balun made in the fashion you've
described only with 12 turns would do reasonably well at 14 through 30,
less than adequate at 7, and perform only marginally well at 4MHz. He
explained that it is difficult to get a sufficient number of turns on a
toroid to supply sufficient blockage to "I3" to do the job across the
whole HF band.
Walt's choke balun, as described above, is only about a foot long in a
beam model, low profile and, above all, it works! 
This doesn't speak well for what you have in hand, I realize, but it's
"the facts," as you requested!
Good luck with the project,
73,
Press Jones, N8UG, The Wireman, Inc., Landrum, SC, 29356
Sales (800)727-WIRE(9473) or  orders@thewireman.com
Tech help (864)895-4195 or  n8ug@thewireman.com
http://www.thewireman.com  and the WIRELINE news 
and bargain page.  Our 22nd year!


On Thu, 15 Jul 1999 12:04:44 +0000 alsopb <alsopb@gloryroad.net> writes:
>
>Guys,
>
>I have sitting on my desk a commercial bauln which
>is a 1:1 design.
>
>The "design" consists of about 6 turns of about
>pencil diameter coax wound on a toroid.
>
>I'm more used to designs with multiple windings or
>bead baulns.
>
>I'm interested in using this to feed my 402CD 40
>meter beam (50 ohms at
>the antenna feed)
>
>Questions:
>
>Is this a valid "bauln" design?
>
>Does it really transform unbalanced to balanced?  
>I'm convinced from past experience that best beam
>performance occurs when the feed is truly
>balanced.  
>
>Is it just a shrinkage (because of the toriod
>permitivity) the 12 turn coax design which guys
>seem to have both success and failure with?
>
>Has anybody used similar designs on their 402CD?
>
>73 de Brian/K3KO
>
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