Are you now claiming that the thousands of bead choke baluns in use for
decades at HF and 6M dont work?
I suspect that those who have been happy with the results in mimizing
feedline radiation would heartily disagree....
Carl
KM1H
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <topband@contesting.com>
Sent: Tuesday, May 21, 2013 11:58 AM
Subject: Re: Topband: Thanks!
On 5/18/2013 10:35 AM, Charlie Cunningham wrote:
If you get the larger beads/tubes thatwill fit over RG-213 etc. you can
make excellent 1:1 current baluns by slipping them over the cable before
putting the connector on.
These are not "excellent" 1:1 current baluns below about 75 MHz. Below
that range, they are a lousy common mode choke, because they are
inductive. Inductive chokes resonate with a line that is capacitive, so
they actually increase the current. A line shorter than a quarter wave is
capacitive; so is a line between a half wave and 3/4 wave. And so on.
That's why we want a choke that is highly resistive -- the resistive
component always reduces common mode current, which is the objective of a
common mode choke (the so-called "current balun.")
There's an extensive discussion of this in my RFI tutorial, and also in
the Coax Chokes power point (which is a pdf). On my website.
k9yc.com/publish.htm
73, Jim K9YC
All good topband ops know how to put up a beverage at night.
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All good topband ops know how to put up a beverage at night.
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Topband Reflector
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