[Elecraft] Home made Sigma-GT5 & KRC2 or SGC?

[Alan WB6ZQZ]

Vertical dipoles can easily have more than 90% radiation efficiency. 
Locating them above ground reduces their ground losses somewhat as compared 
to ground mounted verticals with a few conventional buried radials. They 
have a smaller footprint and are suitable for use for many who do not have 
enough room for conventional radial systems. Even systems with fairly large 
numbers of radials do not exhibit significant gain over the vertical 
dipole, eg less than 1 db in modelling studies by W4RNL.

Mounting vertical dipoles too high above ground causes loss of power into 
(generally) undesirable high angle lobes. So there is a tradeoff between 
ground loss and lobe loss.

Vertical dipoles at the edge of seawater produce tremendous low angle 
signals - exceeding all but the most extreme beam/tower combinations. This 
can probably be replicated by a few miles of copper groundplane around the 
vertical. Reports of comprehensive tests of this kind have not been 
substantiated.

-- Alan WB6ZQZ


From: Earl W Cunningham <k6se@juno.com>
Date: Sun, 21 Mar 2004 10:40:20 -0800

Mike, K5PU wrote:

"I am becoming a big fan of vertical dipoles because they are small
footprint, don't require radials...."
==========
The myth about half-wave verticals not needing radials has been around
for quite some time.

The radiation resistance of a half-wave vertical is still only 72 ohms
and unless the antenna is quite high above ground, it is still subject to
the same ground losses as any vertical unless a good ground radial system
is beneath it.