Any one have an idea of how broadbanded a "ZL Special" is? We're going to
put one together for field day and wonder what 40 meter freq to cut it for.
If it's generally narrow band, we'll have to make a choice between the CW
and phone portions of the band. If it's wide, maybe we can get away with
something in between.

Phil, KB2HQ

Try the "Field Day Special" instead. Go to http://www.eznec.com/miscpage.htm
for the software for designing one. They can be easily made to rvs the
pattern with the flick of a switch.


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. 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.




"Phil" wrote in message
...
Any one have an idea of how broadbanded a "ZL Special" is? We're going to
put one together for field day and wonder what 40 meter freq to cut it
for.
If it's generally narrow band, we'll have to make a choice between the CW
and phone portions of the band. If it's wide, maybe we can get away with
something in between.

Phil, KB2HQ