[TowerTalk] elevated radials vertical

[Tom Rauch]

> One of the new Generals in town has purchased a 30ft 
> pushup mast, the 4 band
> Hustler trap vertical (around 21.5 ft) and wants someone 
> to install this for
> him with the mast bolted to a side of his house. Hustler 
> shows elevating the
> antenna similar to what he wants to do (actually he wants 
> someone else to do
> the work), with 2 radials for each of the 4 bands.

The goal of any antenna manufacturer is to sell antennas. 
That's the payback they get for the work and investment they 
do.
It is unlikely anyone selling an antenna is going to give 
the minuses, and ALL antennas have minuses, anywhere equal 
weight with the pluses.

The only possible way to know if an antenna is really 
working is to A B compare the antenna against a known good 
antenna AT THE SAME LOCATION in many blind tests, or to 
carefully measure things at a good clear test site. A good 
marketing person will make the installation seem very simple 
for everyone because most people won't know if the antenna 
is 10dB down from something else.

You can see what happens with antennas having marginal 
grounds, and even FOUR elevated radials far above earth are 
a marginal ground so far as terminating the shield, by 
looking at this page:

http://www.w8ji.com/verticals_and_baluns.htm

You can see with four perfectly symmetrical radials in a 
perfect environment there is still nearly as much current 
flowing over the shield (for some cable lengths) as there is 
in the radials!! That current is about 20% of the current in 
the antenna!

The closer to earth and the fewer the radials the worse this 
problem becomes.

This doesn't mean the fellow won't "get out", and he might 
be happy with the system...but we shouldn't believe the myth 
that a couple radials makes a perfect ground. That's a big 
ole tall tale.

> I've tried to get him to ground mount the vertical close 
> to the center of
> the backyard and put his radial system in the ground a few 
> inches. He
> doesn't think that is a very good idea.

It's a complex picture Mike. He will gain signal level on 
higher bands by getting the antenna up out of the clutter in 
a yard, he will lose signal level on all bands...especially 
low bands....by not having enough radials. He will also have 
some feedline radiation, maybe even major feedline 
radiation,  unless he gets rid of the common mode current on 
the feedline.

There is always guesswork when deciding what compromise is 
the lesser of two evils. One guess is as good as another. 
Out here in the open I don't worry about ground mounting, I 
just use enough radials. There isn't any clutter. In the 
city I would probably  roof mount if possible and lay as 
many radials as possible on the roof, or better yet use a 
dipole.

73 Tom