Gene,
Yes, with new software etc, may improvements are possible. See my EMail to
K3BU for more info.
73,
Joe, W1JR
At 12:36 AM 1/14/2003 -0500, EUGENE SMAR wrote:
>Joe:
>
> 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
>consideration.
>
> 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 <W1JR@arrl.net>
>To: EUGENE SMAR <spelunk.sueno@prodigy.net>; TowerTalk
><Towertalk@contesting.com>
To: <towertalk@contesting.com>
>Date: Monday, January 13, 2003 8:54 PM
>Subject: Re: [Towertalk] 100M-long boom Yagi for 20M
>
>
> >Gene,
> >
> >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
> >Yagi.
> >
> >73,
> >
> >Joe, W1JR
> >
> >
> >At 12:09 AM 1/12/2003 -0500, EUGENE SMAR wrote:
> >>TT:
> >>
> >> 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
> >>Magazine.
> >>
> >> 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
> >>values.
> >>
> >> 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
> >>
> >>
> >>_______________________________________________
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> >
>
>_______________________________________________
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>See http://www.mscomputer.com
>
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>888-333-9041 for additional information.
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