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[TowerTalk] rf choke or balun?

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Subject: [TowerTalk] rf choke or balun?
From: (
Date: Mon Jun 2 12:27:59 2003
In a message dated 6/2/03 8:59:01 AM Pacific Daylight Time, 

> What am I missing here--I don't understand the difference between a "balun"
>  (at least a 1:1 balun) and a "choke."  Possibly K9MI is referring to a 4:1
>  (or something else other than 1:1) balun?
>  Aren't they in fact the very same thing?  If they each were in a "black
>  box," would they not both appear the same? 

    A balun is a balanced (antenna) -to- unbalanced (coax) transformer 
typically wound on some sort of ferrite core. The newer versions are the 
type". There are a couple of good books on the subject.

    An RF choke is a air wound coil at the antenna end of a coax run. It 
'chokes' RF from going down the coax shield but does nothing for the 
balanced-to-unbalanced feedline/antenna situation. 

    An important purpose of these devices is to keep the outside of the coax 
shield from radiating - an important consideration for RFI problems. 

Steve     K7LXC
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