Topband: Directional Receive Antennas

[Doug Waller]

> If grounds are a problem, I might suggest an array of two flags or
> pennants. It works about as well as a 550 foot beverage, takes up a lot
> less real estate, and doesn't require any grounds at all.
> Larry - W7IUV

Very interesting Larry.  Using my 5 hours of modeling experience with EZNEC
Demo, I had found a 3 element vertical array with the standard cardioid
azimuth pattern, but it showed a much lower elevation pattern than the Flag.
Not willing to accept that there is no way to narrow the cardioid, using
short phased vertical wires spaced about 20-30 feet apart, total antenna
length, I kept thinking.

Using simple vertical wires as elements had its shortcomings, but what about
replacing those elements with something which inherently received poorly off
the sides.  Immediately the small receiving loop came to mind, with its deep
side nulls and general side rejection.  I modeled two square loops separated
by 20 feet, and in line with each other.  The resulting azimuth pattern
rivals the 4 square, but it still exhibited the tall elevation pattern of
the Flag, even when the loop's horizontal wires were shortened & its
vertical wires lengthened.  With an 84 degree, 3db beamwidth & 40 db F/B at
20 degrees, however,  I believe this antenna could be the next step forward.

I am told that when real transmission lines are added & the model is put
into the real world, the good patterns on paper are degenerated & that
wildly swinging reactances kill most ideas.  But I am more convinced now
than ever, that a low noise receive antenna solution is right around the
corner for those of us confined to small real estate.  A really directional,
rotatable receive antenna could not only be the answer to hearing very weak
DX signals, but could reduce or eliminate QRM as well.  Gentlemen, start
your innovation engines!

73/ DX, om Doug / NX4D