[Elecraft] Balanced tuners

[David A.Belsley]

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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