Ralph Mowery wrote:
Over the years I have seen many patterns for horizontal dipoles and the
inverted V antennas,but do not recall seeing any V shaped patterns in the
books. That is a dipole that is supported on the ends, but sag in the
middle. I know the sag is needed to some extent because of the weight of
the wire and feedline, but what happens to the pattern if it is say 1/2
wavelength or 1/4 wavelengths at the ends and the sag in the middle is
changed. Maybe drop it a few feet, then 10, 15 and 20 feet for 80 meters.

I know that for maximum distance you usually want the high current portions
up high,but maybe it will be better as a close in or omnidirectional antenna
if the center is lowered somewhat.



In free space, there is not much difference in pattern between a dipole
that is perfectly horizontal and one that is drooped or sags (or for
that matter one that is bent horizontally). What changes is the
feedpoint impedance (72 ohms for perfectly flat, getting towards 50 ohms
with a 120 degree included angle).


The other thing that changes is the apparent height above ground. If
you model a drooped dipole and fiddle with the height to try and match
the vertical pattern for a perfectly flat dipole, you find that the
"effective center" of the drooped dipole is around 1/3 of the droop
distance. That is, if you had a dipole where the center were at 100ft,
and it drooped 30 feet on either end, the pattern is about the same as a
flat dipole at 90 ft.

The height above ground has a HUGE effect on the dipole pattern
(especially at low elevation angles) and probably dominates any small
changes.

After all, a perfect dipole has a gain of 2.15dBi and a infinitely short
dipole has a gain of 1.6dBi, and a drooped or sagging dipole pretty much
has to be somewhere in between.