[TowerTalk] Vertical balun

[Pete Smith]

At 07:41 AM 12/19/03 +0100, SM2EKM wrote:
>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.


I think it was W8JI who pointed out that effective placement of bead chokes 
on feedlines can be somewhat mysterious unless you can somehow sniff out 
the current on the shield, so Jim's advice strikes me as right on.  It's 
also not unreasonable to think about putting more than one on a feedline -- 
for example one might put one right at the feedpoint, and one at the point 
where the coax enters the house.  I would also check the towertalk and 
topband reflector archives for his very sound advice on what mix of ferrite 
to use for this purpose, because he says the wrong ferrite in a 
transmitting application can generate a lot of heat with QRO power, 
possibly even destroying itself.


73, Pete N4ZR
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