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Re: [TowerTalk] Auto tuners, Baluns and open wire feeders

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Auto tuners, Baluns and open wire feeders
From: Michael Tope <W4EF@ca.rr.com>
Date: Wed, 18 Jul 2018 09:22:08 -0700
List-post: <mailto:towertalk@contesting.com>
On 7/17/2018 1:19 PM, Wes Stewart wrote:
The man wants a simple, single wire antenna.  How the heck is choking at the input end of a short length of open wire significantly better that doing it at the feedpoint?

I know you and Dean are buddies, but don't get me started about him.  Since he's using his software which has been shown to be in error in the past, "Introducing an Improved Version of Transmission Line for Windows Software"  QST, Jun 2014, p.39, I wouldn't make bank on the conclusions.  Plus he continues the fallacy that a balun on the input of a tuner is better than one on the output.  Shown to be wrong by W7EL, W8JI, W9CF among others. ARRL's publication of such an unbalanced tuner and pretending it's balanced is a disservice to the community.

Wes,

If you look at the referenced article ("Don't Blow Up Your Balun"), the point that N6BV makes is that the differential mode loss can be greatly reduced when you put the balun/choke in front of the tuner instead of after it. The point that W9CF, et al made is that putting the balun/choke ahead of the tuner doesn't lessen the common-mode stress (nor does it improve the common mode attenuation). Thus, if the balun/choke is catching fire due to differential mode heating when it is placed after the tuner, moving it in front of the tuner may help. On the other hand, if it is catching fire due to common-mode stress, moving it won't help.

73, Mike W4EF.........

I agree with your recommendation of fan dipoles, but that is beyond the scope of the OP's desires.

Wes  N7WS

On 7/17/2018 11:32 AM, Jim Brown wrote:
On 7/17/2018 11:00 AM, Wes Stewart wrote:
If your open wire is short, why bother? Replace it with low loss coax, put a decent common-mode choke at the feedpoint and tune it.  Sometimes the effort to use open wire simply isn't worth it.

Caution on this. See JUN 2015 - QST (PG. 30) "Don't Blow Up Your Balun"
by Dean Straw, N6BV

Dean's work clearly shows why it simply is not practical to choke a non-resonant antenna. And, because receive noise is such a major issue for most of us, it's why I don't recommend antennas like this. The random wire and off-center fed wires were great ideas for 30 years ago, but terrible ideas today.

Fan dipoles are a FAR better choice.

73, Jim K9YC

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