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[TowerTalk] Force 12 C-3 series.. antenna theory behindthem?

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Subject: [TowerTalk] Force 12 C-3 series.. antenna theory behindthem?
From: (Joe Reisert)
Date: Wed, 10 Mar 1999 19:38:58 -0500
Lou and George,

This type of multi-banding on dipoles etc.has been in the technical papers
for some time. It first appeared in the early 1980's on the Hygain Explorer
14 which patented the idea under the name of Roger Cox, WB0DGF. Later, it
was expanded upon by Gary Breed, K9AY, who also got a patent on same
explaining how to design a dipole with simple math. I believe he wrote it
up in the last ARRL Antenna Compendium. Gary is on the AntennaWare
reflector and has discussed it there too.

I discovered this technique independently in 1991 and designed a few dual
and triband Yagis including a WARC 30/17/12 tribander. I guess I didn't
realize what I had hi! Typically the lowest frequency is a full length
center fed dipole with coupled parasitic dipoles at the higher frequencies.
The parasitic dipoles are approximately a half wave long at the desired
higher frequency and typically spaced 3-10" from the driven dipole.

The new SkyHawk triband Yagi by Bencher uses this technique. It's a neat
trick albiet not very broad band unless multiple parasitic dipoles are used
at the same frequency.

I hope this gets you started. 

Joe, W1JR

At 12:00 AM 3/11/99 +0000, George Claussen wrote:
>At 01:24 PM 3/10/99 -0600, Lou Sica/ AC0X wrote:
>>Could anyone direct me to any references on the web or on hard copy that
>>discuss the theory behind the Force 12 C-3 antenna designs? In particular
>>how the 20m driven element "feeds" the other driven elements, and how the
>>antenna winds up being "resonant" on 18 and 24 Mhz even though it wasn't
>>particularly designed for that (I've even heard they'll tune on 6m). I've
>>read the short article on "Open Sleeve Antennas" from the ARRL Antenna Book,
>>but I'd like to learn some more.  >Thanks to all, (signed by Lou)
>Same here, concerning the theory. I would like to apply the principle
>to a multi-band dipole for 40 and 80 meters. I have applied my very very
>limited modeling skills to the problem, and thus far have come up empty.
>And, I really don't understand the ARRL writing on the subject. All notes
>(reading this L.B.?) on the subject will be most appreciated!
>73, George N7GC, Grayland, Washington

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