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[Towertalk] 100M-long boom Yagi for 20M

To: <>
Subject: [Towertalk] 100M-long boom Yagi for 20M
Date: Tue, 14 Jan 2003 00:36:23 -0500

     Thanks for the note.  You're right regarding K6STI's influence on this
project.  The original article has a footnote that states: quote The authors
thank B. Beezley for the full NEC final analytical calibration, which was
within 0.1 dB of the MININEC results. unquote.  Within the article itself
the authors refer to their use of quote Recently-available MININEC-based
multiple optimization software unquote, which is also referred to in another
footnote as being sourced by Brian.

     On the poor F/B, etc., the authors state quote The elements are
arranged for a considered balance among forward gain, sidelobe level,
impedance level, and bandwidth, ... with ... emphasis on forward gain.
unquote.  I'm inferring here that F/B was secondary in their design

     The overall tenor of the article is look what you can do these days
with some good software to handle the electrical and mechanical design of
REALLY BIG Yagis.  With my little SS tower at 64 feet, I was impressed!

73 de
Gene Smar  AD3F

-----Original Message-----
From: Joe Reisert <>
To: EUGENE SMAR <>; TowerTalk
To: <>
Date: Monday, January 13, 2003 8:54 PM
Subject: Re: [Towertalk] 100M-long boom Yagi for 20M

>According to Brian Beezley, K6STI, this long Yagi antenna was designed and
>optimized with his YO (Yagi Optimizer) software. In fact, the program has
>the "W6TSW" antenna in the demonstration file. I took a quick look and
>wasn't too impressed with the poor (16.59 dB) front to back ratio and the
>high (14 dB down) side lobes at about +/-40 degrees from the main beam.
>Also, the pattern rapidly deteriorated off the design frequency.
>Next, from California, Europe only subtends a very narrow azimuth angle
>(compared to the East Coast) so the narrow half power beam width is
>probably acceptable from W6-land,
>I have built some VHF designs that can be scaled to 20 meters that will
>match the beamwidth and meet or exceed that gain on a shorter boom with a
>much cleaner, broadband pattern and match directly to 50 Ohms!
>That being said, it sure was a novel idea and a way to configure a long HF
>Joe, W1JR
>At 12:09 AM 1/12/2003 -0500, EUGENE  SMAR wrote:
>>      I was going through some old mags in the basement today and found a
>>couple of articles of interest (I hope) to TowerTalk related to Yagis.
>>are both from the June 1991 issue of IEEE's Antennas and Propagation
>>      The first, A Modern Giant Yagi, was written by W6TSW, W6VPH and
>>It describes their work on a 13-element, 100-meter long boom (!) Yagi for
>>20M.  The Yagi was constructed on six colinear towers on a hilltop in
>>Southern California.  The top guy set of each tower is dielectric
>>according to the authors.  One tower supports what looks like a
>>three-element 20M Yagi - Refl/DE/Dir 1 of the array.  Each of the
>>five towers supports a wide-spaced 2-element Yagi (Dirs 2-11).  The photos
>>show all of the booms pointing in the same direction.  The plane of the 13
>>elements (tower height) is said to be 25M AGL.
>>      Specs are:  fixed azimuth of 15 degrees east of true North (don't
>>start!), covering selected portions of Europe and Asia; design freq:
>>MHz; predicted directivity: 15.8 dBi freespace/21.5 over low conductivity
>>ground; 3 dB beamwidth: 15 degrees either side of boresight.  Each element
>>is built with heavy wall Al tubing, starting with 32mm diameter, stepped
>>twice, and ending with 19mm at the element tips.  Each of the six,
>>75mm-diameter boom segments measures 9M long.  On-air reports of this
>>behemoth vs a wide-spaced 5-el Yagi support the calculated performance
>>      The second article is A Secret Story About the Yagi Antenna, written
>>Prof Gentei Sato of Sophia University, Tokyo.  The article recalls his
>>to locate Newmann's Note, a set of papers reportedly recovered from a
>>burning trash pile after Japan's conquest of the British fortress in
>>Singapore in February, 1942.  It was from these notes, written by British
>>POW Newmann (variously identified in the article as Private, Corporal or
>>Master Sergeant) that Japanese engineers and military staff first learned
>>the Allies' effective use of the Yagi antenna in RADAR.  Up until then,
>>Yagi-Uda antenna, invented in Japan in 1926, had been used by the Japanese
>>in only two radio links to connect two off-shore points to the mainland.
>>The author comments that he himself learned during a visit to the
>>Smithsonian Institution in DC the the two atomic bombs that devastated two
>>of his country's cities included Yagi antennas as part of the
>>altimeter/detonation circuit.
>>      I found both of these articles to be a fascinating and colorful bit
>>background on an invention that we TT'ians almost take for granted - the
>>venerable Yagi-Uda antenna.
>>73 de
>>Gene Smar  AD3F
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