[Elecraft] EC! competition: Balanced auto ATU

[Jerry T Dowell]

Kirchoff's Laws say you are wrong, Don. See Al Roehm's article "Some
Additional Aspects of the Balun Problem" , on page 172 of "The ARRL Antenna
Compendium", Vol. 2, or the corresponding QST article. A single-ended LC
network will do just fine feeding a balanced line if the network itself is
fed with a good current balun. The currents on the balanced line will be
equal and opposite, thanks to Kirchoff (and Mother Nature).

Jerry,  AI6L

----- Original Message -----
From: Don Wilhelm <w3fpr@peoplepc.com>
To: Jonathan Taylor, K1RFD <K1RFD@k1rfd.com>; Elecraft
<elecraft@mailman.qth.net>
Sent: Friday, February 08, 2002 4:05 PM
Subject: Re: [Elecraft] EC! competition: Balanced auto ATU


> Gang,
>
> Putting the balun ahead of the tuner and floating the tuner will not
result
> in a balanced output!!!
> The result will be a balanced input to the tuner (due to the balun), but
> because the inherently unbalanced tuner design will not present the same
> impedance for each leg of the transmission line that follows it, the
balance
> will be upset right at the output of the tuner.
>
> Sorry folks, we just can't fool mother nature.  I realize that there have
> been several tuner designs that use this principle, and some report good
> balance, but I often wonder what the test conditions where when the
balance
> measurements were made.
>
> 73,
> Don Wilhelm  - Wake Forest, NC   W3FPR home page:
http://www.qsl.net/w3fpr/
>   QRP-L # 485   K2  SN 0020   mailto: w3fpr@arrl.net
>
> ----- Original Message -----
>
> > One technique is to put the balun *ahead* of the ATU, and "float" the
ATU.
> > That way, the balun always sees the same impedance, yet the output is
> > balanced.
> >