[Elecraft] HF Verticals?

[k6se@juno.com]

Stuart, K5KVH wrote:

"IF a quarter wave type, it HAS to have SOMETHING to replace the other
missing half of the antenna.  The near half wave verticals can do that,
without added radials, or ground screen in near field below.  The quarter
wave must have help be it radials, elevated or ground, or a plane or
screen."
==========
While I agree with the rest of Stuart's post, I must take exception with
his statement about 1/2-wave verticals (either dipoles or end-fed) and
elevated radials.

One of the most common misconceptions is that a low 1/2-wave vertical
does not need radials.  If a good radial system is not placed on the
ground below this antenna, the same amount of energy heats up (is lost
in) the ground just as much as it would with a 1/4-wave vertical.  The
only way around the ground loss problem is to make the center of the
vertical at least 1/2-wave above ground, and preferably much higher.

The same is true about a 1/4-wave vertical with elevated radials (unless
there are as many radials as there would be if the vertical was
ground-mounted).  Many hams on 160m use only 4 elevated radials 10 feet
high or less, thinking it will work as good as an on-ground system with
60 radials.  10 feet is less than 0.02 wavelength on 160m, so those 4
radials act the same as if they were on the ground or buried, therefore
the same ground losses apply for the "elevated" system, so the ham using
a low, elevated radial system is disappointed in the results compared to
those who use extensive ground radial sustems under their verticals. 
Although the antenna will work, most of the power is lost in the ground. 
This has been proven by far-field field strength measurements by others
who have investigated on-ground versus elevated radial systems.

For a 4-radial elevated system to be any good, it must be *at least*
1/4-wave high.  Even at that height the antenna efficiency suffers due to
ground loss.

Ground screens have also been investigated.  While they are ok if they
extend away from the base of the vertical as far as an extensive radial
system would, the radials are still better (and far less expensive).

73, de Earl, K6SE