[Antennas] Half-Square Question

[Robert Lay]

Dear Ron,

I went through that too hurriedly and messed myself up. As good as
it sounded at the time, you are quite correct - the flat top portion has to
be 1/2 wavelength.

Let's take it from there and see how it goes.

Again, the flat top portion is a so-called phasing section. By the time the
signal gets to the far vertical portion, it has been delayed by 1/2
wavelength or 180 degrees. That should be that same as if I had simply
applied the same signal to two verticals that are 1/2 wavelength apart but
the two signals that I am generating are exactly 180 deg out of phase with
one another.

The classic 2 vertical, directional antenna is described in the ARRL Antenna
Book on page 4-10 of the 17th Edition, as follows:

Two or more vertical antennas spaced 1/2 wavelength apart can be operated as
a single antenna system to obtain additional gain and a directional pattern.
...snip... In the broadside configuration, the two verticals are fed in
phase, producing a figure-eight pattern that is broadside to the plane of
the verticals. In an end-fire arrangement, the two verticals are fed out of
phase, and a figure-eight pattern is obtained that is in line with the two
antennas, Fig 19. However, an end-fire pair of verticals can be fed 90 deg
out of phase and spaced 1/4  wavelength apart, and the resulting pattern
will be unidirectional.

So, I erred in my previous description. The antenna that I described with
only 1/4 wavelength flat top would produce a cardioid or unidirectional
pattern. The true half-square antenna should produce the
end-fire pattern, as stated in the reference.

Bob Lay (W9DMK) in Dahlgren, VA
http://www.qsl.net/w9dmk