[Top] [All Lists]

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

To: <>
Subject: [Towertalk] 100M-long boom Yagi for 20M
From: (Joe Reisert)
Date: Mon, 13 Jan 2003 20:33:09 -0500

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.  They
>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 K6BLG.
>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 material,
>according to the authors.  One tower supports what looks like a wide-spaced
>three-element 20M Yagi - Refl/DE/Dir 1 of the array.  Each of the remaining
>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: 14.150
>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 by
>Prof Gentei Sato of Sophia University, Tokyo.  The article recalls his quest
>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 of
>the Allies' effective use of the Yagi antenna in RADAR.  Up until then, the
>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 of
>background on an invention that we TT'ians almost take for granted - the
>venerable Yagi-Uda antenna.
>73 de
>Gene Smar  AD3F
>AN Wireless Self Supporting Towers at discounted prices,
>Wireless Weather Stations now $349.95. Call Toll Free,
>888-333-9041 for additional information.
>Towertalk mailing list

<Prev in Thread] Current Thread [Next in Thread>