[Elecraft] Vertical antennas

[Darwin, Keith]

Good info Steve,

I wonder a couple of things though.  First, why 8 degrees for the
takeoff angle?  That puts it low enough that you're into the ground
effect suck-out zone fairly heavily.  I'd have though something like 25
degrees would be a more representative angle for typical communications
use.

Also, what is the effect on the Force 12 antenna if it is between 1 foot
and 28 feet off the ground?  What if it is 15 feet off the ground (i.e.
on my garage roof)?

- Keith N1AS -
- K2 5411.ssb.100 -

-----Original Message-----
From: Stephen W. Kercel

The discussion of verticals has inspired me to do a bit of EZNEC
modeling. I plotted the azimuthal pattern at an 8 degree takeoff angle
for several different 80 meter configurations. In all 3 cases, I've
assumed average ground.

The first case is the classical full size vertical, with a quarter wave
monopole element and 128 quarter wave radials. *snip* the pattern is an
omni pattern with a signal strength at 8 degrees takeoff angle of -2.72
dBi.

The second case is the Force 12 vertical dipole, with no radials. ...
bottom of the antenna elevated 28 feet above the ground. ... The signal
at 8 degrees takeoff angle is an omni pattern at -3.09 dBi. ... an
undetectable quarter dB worse than the ideal full size quarter wave
configuration.

How important is the mounting height? It matters. For the same
configuration except with the bottom 1 foot above the ground, the signal
strength at 8 degrees takeoff angle is -5.8 dBi. This is a quite
noticeable >3db degradation from the full featured quarter wave
configuration.