[Towertalk] grounding an elevated vertical

[jljarvis]

Seems to be a lot of people wading in with absolute authority
on what is an "it depends" topic.  What it depends upon is 
ground conductivity, for the most part.

There was significant quantitative work done on 1/4 wave verticals
with elevated radials, in the late 70's and early 80's.  This was
intended for AM broadcast use, but the experimental work was carried
out at 1.8 MHz by amateurs who are also consulting engineers.

To be sure, copper plating earth will improve the performance of a
vertical.  It's a question of marginal improvement in efficiency
versus expense.   120 buried radials are the broadcast norm.  But
16 radials will get you to 90% efficiency.  And 3 or 4 elevated radials
will do the same.  

Empirical data presented to the FCC showed that 4 radials, elevated @ 10'
were the equivalent of 120 buried radials, in terms of field strength.
If I recall the experiment, though, there were REMAINS of those 120 radials
still in the earth, and the ground conductivity was exceptionally good.  

No matter what you do...you're at the mercy of your ground conductivity.
If it stinks....rock and sand, like mine....you could improve it by installing
buried radials...but in truth, that isn't going to happen, here.  

Short form:  Put the antenna up as high as you can...get the radials as high
as you can.  Put at least one in each desired direction...the vertical angle
distribution of energy will tend to be higher where there is no radial....and
'normal' where there IS a radial.  The reason to get as high as possible is to
minimize the capacitative coupling with earth, in the near-field.  This will
reduce losses.   A 40m vertical, with the base 1/2 wave in the air...and radials
sloping downward @ 45 degrees or so is a killer.  Kind of hard to do that on 
80 or 160... My elevated radials are around 10' high.  

I would strongly recommend you get the radials above head height for the tallest
critter you expect to see.   A moose took mine out, last fall.

Jim Jarvis
N2EA