[TowerTalk] Balun Question

[Steve Hunt]

Kevin,

I assume by "coax baluns" that you mean air-cored baluns. Air-cored 
baluns have a number of disadvantages:

* They are "high-Q" and exhibit a high common-mode impedance over only a 
relatively narrow bandwidth
* Their common-mode impedance is almost entirely Reactive (rather than 
Resistive); in situations where the common-mode path impedance is 
Reactive but of opposite sign, the addition of the balun can actually 
INCREASE common-mode current.

An effective 1:1 Current balun should have a high common-mode impedance 
which is predominantly Resistive over the frequency range of interest. I 
have a chart on my web site which shows the relative performance of 
several types of 1:1 balun:
http://www.karinya.net/g3txq/chokes/

As you can see, baluns wound on "lossy" ferrite mixes such as #43 or #31 
do best, and toroidal forms tend to make best use of the available 
ferrite material.

73,
Steve G3TXQ




Cycle-24 wrote:
> Hello tower talk experts.  I have been using air wound 1:1 coax baluns for
> years with great success on our antennas.  They are reliable and have never
> failed in the heat of a contest.  However, I've recently discovered
> commercially available, very impressive looking, 1:1 baluns made out of
> ferrite cores enclosed in small weather proof boxes.  The builder claims
> that his baluns are better than using ferrite rods, beads, or air wound
> baluns, but does not give any specifics as to why.
>
> What do people use out there for 1:1 baluns on their dipole or Yagi
> antennas? Is there any real difference between using cores, beads, or air
> wound coaxial baluns?
>
> Thanks,
>
> Kevin N5DX
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