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Re: [TowerTalk] 80m dipole with open-sleeve parasitic

To: jimlux@earthlink.net, towertalk@contesting.com
Subject: Re: [TowerTalk] 80m dipole with open-sleeve parasitic
From: "knormoyle@surfnetusa.com" <knormoyle@surfnetusa.com>
Date: Wed, 19 Jan 2011 14:50:12 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
<I'm going to look at the arrl articles Rick listed>

Jim asked "When you say open sleeve, do you basically mean something where the 
apparent diameter of the conductor is larger (e.g. like cage dipoles, 
bowties, biconicals, and to a lesser extent, fan dipoles)?"

I use "open sleeve" in terms of a second single, parallel parasitic dipole 
element, shorter than than the dipole 
driven element, and parallel to it, but not one cut for another band. In terms 
of whether you should call 
it "loading" ..I think not, since it's not physically in the driven element, 
like normal L we talk about for the 
driven element. I also don't think that the abstraction of saying it's an 
apparent larger diameter is right.

(next we'll argue about how a folded dipole with 6" separation "acts" ! :)

This definition of "open sleeve" is a reduction of the original dual parallel 
wires, or coax, incarnations, but 
commonly described with the same words.

Side note: I was reading Tom Schiller's (Force12) patents on open-sleeve feeds 
for 20/15/10 tribanders.
http://www.freepatentsonline.com/5995061.html

He calls his patent "No loss, multi-band, adaptable antenna"
The "no-loss" might get some eyebrow-raising :)

Curiously, he mentions 1.14x as an interesting minimum frequency delta for the 
parasitic element. Don't know how 
he came up with that.


"17. A low loss antenna comprising: 
a driven element resonant at a first frequency, not resonant at a second 
frequency, and not resonant at a third 
frequency; 

a first adjacent element adjacent to the driven element on a first side of the 
driven element, said first adjacent 
element spaced apart from the driven element and resonant at the second 
frequency, not resonant at the first 
frequency, and not resonant at the third frequency; and 

a second adjacent element adjacent to the driven element on a second side of 
the driven element, said second 
adjacent element spaced apart from the driven element and resonant at the third 
frequency, not resonant at the 
first frequency, and not resonant at the second frequency; and 

a common feed point located at the driven element for coupling to a feedline 
for feeding signal energy to the 
driven element; 

where the second frequency is at least 1.14 times the first frequency, the 
third frequency is at least 1.14 times 
the second frequency, and the third frequency is less than two and one-half 
times the first frequency."


and


"24. The low loss antenna as set forth in claim 17, wherein the electrical 
length of the first adjacent element is 
at least 14% greater than the electrical length of the second adjacent element."


Now the elements here are fatter, and shorter for a 20/15/10 tribander than 
what I'm talking about.. So maybe the 
losses aren't as interesting?
Or just part of a tradeoff

-kevin
ad6z



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