Rick-
I have been reviewing some of the better posts, and I came across this
(below.)
If the "double hump" you refer to is in reference to the figure in the ARRL
antenna book, that is only achieved by decoupling the elements by putting
them at 90 deg apart. Read the "fine print" in the text.
The antenna book treatment of both the fan and the cage is disappointing. Do
you know of a "real" reference?
Bill--W4BSG
----- Original Message -----
From: "Rick Stealey" <rstealey@hotmail.com>
To: <towertalk@contesting.com>
Sent: Saturday, April 11, 2009 8:53 PM
Subject: Re: [TowerTalk] Cage dipole revisited.
>
> Today I did a little modeling with 4NEC2 on 80 meters. First a regular
> dipole showed a bandwidth of 200 KHz at the SWR=2:1 points.
> Then I decided to see how close to a real cage a pair of dipoles has to be
> to get the same benefit. So I added another dipole, fan style, to it and
> got 320 KHz bandwidth. I varied the length of the second dipole all over
> the place. I was modeling on 80 meters, and made the 2nd dipole small
> (like the length of a 40 m dipole) and could see SWR dips in the 80m and
> 40m bands when I did a frequency sweep. Then I lengthend the small dipole
> and watched the 2nd dip drop in frequency till it got close to the 80 m
> band and the bandwidth began increasing. But I was never able to get a
> "double hump" inside the 80m band as I had hoped.
> But 320 KHz bandwidth was easily obtained.
> Now the question is, how different is a pair of dipoles (with 10-20
> degrees angle between them)from a real cage dipole ? So to do this I
> modeled three dipoles, parallel to each other and separated a few feet
> apart. The bandwidth was the same as the fan, indicating to me that very
> likely a simple two dipole fan antenna (both elements can be the same
> length) will give good swr performance compared to a dipole and might be
> worth the effort. Sure would be simple to build compared to a cage
>
> Rick K2XT
>
>
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