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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