[TowerTalk] 80-m. Inverted Vee vs. Dipole Performance, RLVZ <=

[Rob Atkinson]

You're never going to get the dx low angle you want with any inverted
V or horizontal wire antenna on 80 meters if you are limited to 50
foot supports such as the tower you have.

The problem with inverted Vees is most hams do not elevate them
adequately.   The overall performance height of an inverted V is the
average between the feedpoint height and the height of the ends.  If
the apex is 50 feet high and the ends are 15 feet high you have the
same thing as a dipole flat top 32.5 feet high.  Hams like the
inverted V because it usually needs one major support and is okay for
casual operating.   But if the ends, where voltage maxima are, are too
close to ground (15 feet is too close) you loose signal to ground via
close coupling to earth off the ends.

Hams get good performance on 80 m. with inverted Vees (not necessarily
good DX but at least high efficiency) if they can get the feedpoint up
at about 120 feet, and tie the ends to 30 foot phone poles about 150
to 200 feet distant on each side.  This results in a long span of rope
for the antenna wire is only about 70 feet of the distance, making a
wide V angle (almost a flat-top) and keeping the average height of the
whole thing high.

Few hams can pull that off, so it is better to have a flat top dipole
with two or three supports keeping it at high average height as much
as possible (as close to 1/4 wave high as possible) to minimize ground
loss, but in your case since DX is your primary objective, your best
bet is to use the tower to hang a wire off the side and make an
inverted L with about 50 feet vertical and 30 feet horizontal, tuned
with a capacitor at the feedpoint, and several 1/4 w. radials on the
ground.

What about a vertical dipole?  The problem there (and why you are
better off with a base fed 1/4 w. vertical monopole in the form of the
L), is that vertical dipoles have half the charge density for a fixed
power level because it is spread over a lenth twice as long.

That solves your tx situation but on the low bands these make for not
very good rx antennas so for dx you will probably have to use
something separate for receiving, such as a beverage, flag, pennant,
or small tuned loop.

73

rob
K5UJ