Look at: ftp://eznec.com/pub/
73'
Paul i1odp
The "Field Day Special" Antenna
The Field Day Special is a two-element wire beam with a unidirectional
pattern. It's similar to the "ZL" special, except that its elements are the
same length. This makes it easy to reverse the pattern by using two
feedlines, one at the center of each element. The original antenna was
described in June 1984 QST. An antenna like this can't directly be scaled
for other bands unless the size of the twinlead it's made from is scaled in
proportion. However, using the program available here, you can design your
own for the frequency band of interest. By changing the various dimensions,
you can trade gain/beamwidth, feedpoint impedance, and bandwidth.
Improvements in the program have been made since the article was published,
so an optimal design for 20 meters will have dimensions slightly different
than the ones shown in the article. The currents in the elements of one
design were measured and found to agree very closely with those predicted by
the program. Quite a number of these have been built by various people for
several bands, with universal reports of operation as predicted. I use a 20
meter version nearly every year for Field Day, and occasionally 15 and 40
meter versions as well. 20 and 15 meter Field Day Specials have been my
primary home QTH antennas for these bands for a number of years.Go to
ftp://eznec.com/pub/ Download FDSP~.EXE, then follow the directions under
"Downloadable Files", above. More information about the antenna, including
construction and feeding, is included in one of the expanded files. The
program is a DOS program and can be run from the Windows 95/98/NT DOS prompt
----- Original Message -----
From: "Jim Idelson" <k1ir@designet.com>
To: "TowerTalk Post" <towertalk@contesting.com>
Sent: Thursday, January 04, 2001 10:22 PM
Subject: [TowerTalk] Portable tribander design help?
> Hi all. Looks like I'll be in Europe during the ARRL CW DX contest. I'll
be bringing along my IC706 and doing a 100 watt effort for the contest. It
will be an all-band effort with heavy emphasis on running on the high bands.
I'd like to put up a briefcase-portable antenna with gain fixed on the US
for 20-10. Can anybody help out with a tribander design that uses thin wire
elements and a minimum number of traps? Something equivalent to an A3 or
other small tribander would be great! I have EZNEC . . . if you have a
simple tribander model, I'd be happy to start there.
>
> Jim K1IR
>
>
> --
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