From: mac@cis.ksu.edu (Myron A. Calhoun)
Newsgroups: rec.radio.amateur.misc
Subject: Field-expedient broad-band HF antenna (long)
Date: 17 Apr 1992 18:13:02 GMT
Organization: Kansas State University, Dept. of Computer Science
Distribution: world
NNTP-Posting-Host: depot.cis.ksu.edu

The March, 1992, issue of RF DESIGN magazine included an article
"A Field Expedient Broad Band HF Antenna" (pages 135-137) by
Bernard Feigenbaum, U.S. Army CECOM (908) 544-4532.  Although he
wrote about "the varied and demanding requirements peculiar to
expeditions and military tactical communications" instead of Field
Day, his solution for the military should work for Field Day, too!

He began by mentioning (and then discarding from further consideration)
the most obvious field-expedient antennas:  dipoles, sloping vees, and
long-wire beverage antennas; and then he described his solution.
Copied without permission, here are portions of the article:

   "The zig-zag sky-wave antenna has similar impedance and radiation
    pattern characteristics as the log periodic; but does not have
    the super gain quality because it is much smaller.  However, it
    has standard gain similar to a standard half wave antenna.  Its
    advantage is that it occupies less real estate than any of the
    other field expedient antennas.  It can be truly said that this
    is a field expedient, tactical, HF log periodic antenna and the
    principle behind its operation is the subject of a recent patent.

   ".... It combines transportability, electrical performance, easy
    assembly and low cost.  The new antenna makes log periodic
    characteristics available at a fraction of the cost of a full
    size LP antenna.  ....

   "The foregoing and other objectives are achieved in a preferred
    embodiment, both patented and copyrighted, wherein ten inter-
    connected, vertical, zig-zag, antenna sections are of a pre-
    determined increasing height.  The antenna is terminated by an
    appropriate resistance so as to maintain the characteristic
    impedance over the entire frequency range of interest.  A counter-
    poise is utilized to balance the antenna system.  Power is
    coupled to the shortest zig-zag section via a 9:1 broad band
    impedance matching transformer.  The currents that are induced
    on the antenna cause power to radiate at low elevation angles.

   "It is a peculiar feature in that, unlike the conventional log
    periodic antenna, the miniature HF antenna is a non-resonant log
    periodic directional antenna which achieves a single main beam by
    virtue of satisfying the Hanson-Woodyard condition; one of the
    few instances where it is practical to obtain more directivity
    from an array with reduced inter-element spacing.

   "The miniature log periodic antenna has constant impedance and
    radiation characteristics similar to a full size log periodic
    antenna....

   "The miniature antenna is also superior for transport.  ....
    can be erected by one man in 45 minutes in fair weather....

   "U.S. patent no. 4,733,243 was issued for this antenna on March
    22, 1988.  The antenna is available by means of Technology
    Transfer agreements between the U.S. Army and industry."

The small and not-to-scale sketch which accompanied the article looked
something like this (within the limitations of an ASCII drawing):
A sloping rope is used to suspend the wire "mountaintops"        /\
at the ever-increasing heights shown and the      /\            /||\
bottoms of the "valleys".            /\          /  \          / || \
                          /\        /  \        /    \        /  ||  \
                 /\      /  \      /    \      /      \      /   ||   \
          /\    /  \    /    \    /      \    /        \    /    ||    \
     /\  /  \  /    \  /      \  /        \  /          \  /     ||     \
  /\/  \/    \/      \/        \/          \/            \/      ||      \
 |                                                               ||       \
 |                                                               ||   400 | ohm
grounded                                                       mast  termination
                                                                      to ground

The "antenna" was raised one meter above the ground, but I can't tell
if this was the whole antenna or just one end.  Three counterpoises
were shown.

Since this antenna has been patented AND copyrighted, I'm hesitant to
copy any more details to a public net.  The patent should be available
from the U.S. Government for the usual fee.  I'd love to correspond
via "private" email with someone(s) who would repeat the NEC (?) 
simulations hinted at in the article.
--Myron.
-- 
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# Myron A. Calhoun, PhD EE; Associate Professor  (913) 539-4448 home
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