"Buck" wrote in message
news
On Wed, 28 Feb 2007 12:39:36 -0800, "Comcast newsgroups"
wrote:

Hello all,

I have a mono-band 20-meter vertical currently mounted only about
12 feet up (less than a quarter wave). There are 4 radials and it tunes
very well - very low VSWR across entire band, with decent signal reports.

Question: If I were to rent a cherry picker, I could mount the thing on
the end of the peak of my house, at about 40 feet up. That would put the
bottom of the radials at greater than 1/4 wave.

But would I notice any difference? If so, would it be potentially
dramaticly
better, or just 'technically' better? It would be a major project to do,
so
I'm
trying to decide if it would be worth it or not.

Thanks,

Dave WB7AWK



I don't know the minimum height above ground (in wave lengths) that
make the improvement in an antenna. However, Steppir antennas says
that an antenna on the ground needs 120 radials just to match one in
the air with two radials. I would like to know where the noticable
benefit of raising an antenna above the ground actually takes place
and where is the maximum benefit.

I know that the higher the better, but rather than that kind of
benefit, I am wondering from a ground standpoint where the benefits
start and where the point of diminishing returns begins.

Good luck with your antenna.


--
73 for now
Buck
N4PGW

I decided to run EZNEC on a 20 m vertical with 4 radials sloping 45 degrees.
Here is what I got:

HEIGHT GAIN V-ANGLE

15 ft 0.1dbi 19 deg
32 0.54 14 deg
40 1.25 47
0.51 12
100 3.31 8


The 40 foot height has a double lobe, but the gain at 12 degrees is more
than the 15 foot gain at 19 degrees. Now I know why the DL I worked on 20,
with a vertical on the roof of a 24 story apartment building sounded so
good.

Tam/WB2TT