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Re: [TowerTalk] One of our own...

To: towertalk@contesting.com
Subject: Re: [TowerTalk] One of our own...
From: Bob K6UJ <k6uj@pacbell.net>
Date: Wed, 25 May 2016 16:38:59 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Dave,

Wow, forget to take your medication ?

Bob
K6UJ


On 5/25/16 12:20 PM, David Gilbert wrote:

It's ridiculous to say that a loop is always better than a dipole, especially when your only evidence is one anecdotal example. There are some solid theoretical reasons why a dipole might easily perform better than a loop when the supporting structures for each are at the same height. You can choose to be oblivious to those if you want, but the kind of statement you just made is what made ham radio the petri dish for unscientific speculation and bias in decades past. I thought we had mostly progressed beyond that, but apparently not.

To be specific in your case, that narrow bandwidth for the dipole could have meant that it was very efficient ... i.e., high Q ... although a 15 KHz bandwidth is unusually narrow and suggests that you had something else going on. If you understood antennas you would have known that and investigated further instead of just taking it down. Maybe you weren't using a balun and had feedline interactions, or maybe your feedline length just happened to be a problem for that particular setup. Could have been something else as well, but it doesn't make a dipole inherently a bad idea just because there was something wrong with yours.

Your loop likely has significantly higher losses since the bottom portion is so close to the ground, and especially since a significant portion of the polarization would be horizontal (tilted and bottom corner feed). The higher losses would indeed make it tune more broadly and would make it quieter, but it wouldn't make it a "better" antenna if you were trying to actually radiate a stronger signal.

Dave   AB7E



On 5/25/2016 9:01 AM, Courtney Judd wrote:

hey Steve, yes, I did enjoy the article about verticals/beach, very educational! BUT, in the same issue of QST another article "If you can hang a full-size vertical loop, then hang a dipole" really made me roll my eyes. While I have never done any modeling, 50 plus years of playing with various antennas leaves me with the opposite conclusion. A loop is ALWAYS better than a dipole in my experience. I wanted to spend some time on 160 some years back so I strung up a dipole at 110 ft with the resonant point at 1840.00.... worked great.... all kinds of dx.... BUT the 2:1 swr points were only 7.5 kz up and down... even with a tuner the antenna preformed poorly beyond that. It was just un-satisfactory so i pulled it down and replaced it with the 160 antenna I still use today. A full wave loop fed at a lower corner, top at the same 110 ft point. I did have to tilt it 15 deg from the vertical to get it in the property lines but it works like a bandit. It is quiet and broad banded: 2:1 is 1800 to 1890 and works well over the whole frequency! I would NEVER replace it with a dipole. Well, thats my 2 cents and I am sticking to it! lol, 73's Cort K4WI
K7LXC--- via TowerTalk <mailto:towertalk@contesting.com>
Wednesday, May 25, 2016 10:32 AM
Howdy, TowerTalkians --

One of our esteemed members, Grant, KZ1W, has had an article published
in the new QST called "Verticals On The Beach - Some Modeling Results".
It's a well thought out article with actual on-the-air performance compared
to predicted modeling results. A real practical article for anyone
interested in vertical performance.

Cheers,
Steve K7LXC
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