Again, why a balun? StepIR should know better.
If there are RF currents on the braid of the
feedline you need to cut the braid, that is from
an RF point of view. That you do with forexample
ferrite beads, as you correctly point out below.
I would put them as close to the feedpoint as
possible, if that doesnt solve the problem I
would move them.
Why complicate things with unneeded stuff, keep
it correct and simple and it will pay of in the
long run.
Jim SM2EKM
----------------------------------------------------
Tom Champlin wrote:
Well, for instance, I just bought a Big SteppIR vertical. The company
recommends a balun in some cases. They said it was to keep the RF from
coming down the coax. They also sell this balun. Not being a purist, I often
like to use the term balun meaning an RF choke as well as a 1:1 matching
device. Balanced to unbalanced.
I normally just use a string of large ferrite beads at the feed point. I
haven't modeled this with EZNEC yet, but I would bet that the radials will
couple some RF to the coax shield, hence my question as to where to place
the beads, balun, or whatever one wants to call it.
Best regards,
Tom W0HH
----- Original Message -----
From: "Jan Erik Holm" <sm2ekm@telia.com>
To: <towertalk@contesting.com>
Sent: Thursday, December 18, 2003 10:45 PM
Subject: Re: [TowerTalk] Vertical balun
Why a balun?
73 Jim SM2EKM
--------------
Don Havlicek wrote:
Tom,
Good question!
I never used a balun on the 80m vertical, but might when I replace the
coax this Spring.
I'll be interested in reading the responses to your query.
Don
N8DE
Tom Champlin wrote:
The recent discussion of ground radials has been a big help for me.
There is just one other thing that bothers me. Most hams would
probably either run buried PVC to put the feed line in, which would of
necessity be parallel with the nearest buried radials. Even if
everything was above ground, my question would be the same. Assuming
it would be desirable to use some kind of balun on the coax before or
at the vertical feed point, possibly a W1JR toroid type, or some
ferrite beads. The object being to keep RF from running back to the
shack on the coax braid.
So, would one want to place this balun past the radial field but
before the feed line gets close to the house or right at the antenna,
or does it matter?
Tom W0HH
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_______________________________________________
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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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_______________________________________________
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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