Vic: You are right. The URL for the "brief" version of W7EL's paper is
<http://eznec.com/misc/ibalbrf.txt>
and a more detailed version is at
<http://eznec.com/misc/ibalun.txt>.
It's not clear to me why one would want to hang on to a balun in a
balanced tuner. A simple L-C network on the input is very effective
(or a movable link). Someone just posted that their best bet was a
homebrewed transmatch, and I agree with this. A balanced homebrewed
transmatch is a simple project. To be sure, it can be made very
complex if one wants, but that is really unnecessary. I have used my
Italian homebrew with great success for decades. I call it my Italian
tuner because it looks like a plate of spaghetti, but boy does it work.
best wishes,
dave belsley, w1euy
On May 13, 2005, at 11:13 AM, Vic Rosenthal wrote:
David Honey wrote:
A true balanced tuner has the balun at the input where, once the ATU
is propery adjusted, will always be at 1:1 and hence no reactive
elements.
This is not correct. As you suggest, placing the balun at the input
of an unbalanced tuner is an attempt to solve the problem posed by
operating a balun in the output of the tuner, where the impedance is
uncontrolled. However, W7EL (I can't find the reference just now) has
shown that this method is actually no better than the balun in the
output!
A true balanced tuner does not have a balun at all. For example, the
Johnson matchboxes make the unbalanced to balanced transition by using
an unbalanced link coupled to a symmetrical parallel-tuned tank
circuit that is connected to the feedline. There are several true
balanced tuners available: MFJ makes one, and I've seen others. Just
Google 'balanced tuner'.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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