Sorry Mike, POOR CHOICE!
Open your balun (remove the cover) and look at how the two transformers are
wound.
Both transformers have their windings wound over the pair of stacked
toroids. This is bad.
Although it is indeed built to the highest build standards and can handle
high power, it will not work properly as a balun. It only works as a 4:1
transformer, which is not always good.
This balun will force a 3:1 current unbalance in each side of the antenna.
It does not work.
A better 4:1 balun is the Balun Designs 4115ocf.
View the picture of the insides of this Balun and see how the cores are
wrapped differently from the 4125.
In this case, each transformer has its own dedicated core, independent of
the other. THIS ONE WORKS.
The 4125 does it wrong.
Pictures:
http://www.balundesigns.com/servlet/the-75/OCF-balun-4-cln-1/Detail
Steve, G3TXQ has done some measurements which prove this.
Here is what he posted here earlier:
"If you wind a 4:1 Guanella balun as two identical 1:1 chokes on a common
core, you force the CM voltages across the two chokes to be the same because
they share the same flux. If we call the input voltage V, the balun then
drives the output terminals to +3V/2 and -V/2 with respect to ground. If you
had a perfectly balanced load that would force 3 times the current into one
leg compared to the other. Analysis here:
http://www.karinya.net/g3txq/temp/4%20to%201%20current%20balun.png
and here's the experimental demonstration on a 'scope using a perfectly
balanced 200 Ohm load:
http://www.karinya.net/g3txq/temp/bal1.jpg
http://www.karinya.net/g3txq/temp/bal2.jpg
Because of Sevick's pre-occupation with differential-mode performance he
never spotted that effect. In fact he made lots of DM measurements - DM
impedance, phase delays etc - but with a *floating* load; andas we all know,
if you have a floating load you don't need a balun to maintain current
balance :)
The simple fact is that a 4:1 Guanella balun wound as two 1:1 chokes on a
common core will force voltage and current *imbalance* with any non-floating
load; I don't call that "working" !
For a 4:1 Guanella balun to "work" properly and drive equal currents into
any load, the CM voltages of the two chokes must be able to take up
different values; they can't do that if they share the same magnetic
circuit.
73,
Steve G3TXQ'
---
73
Rick, DJ0IP
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Mike
Stricker
Sent: Saturday, July 27, 2013 7:48 PM
To: tentec@contesting.com
Subject: [TenTec] which balun?
Balun Designs 4125T
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