On Sun, 24 Feb 2008 15:15:34 +0100, "Francesco L."
wrote:

Hi Francesco,

On the ground, or elevated?

Both cases please. I did a reasearch on arrl antenna book, low band dxing
and newsgroups and got a bit confused, so I need more tips. There are too
many options, I mean: at a certain height above the ground, atop the roof,
on the ground and so on, so I'm trying to collect as much info as possible
in order to get the overall picture.
Thanks


If you are calling 'low band' those frequencies below the AM broadcast
band, any antenna you use will be of compromise size (less than 1/4
wave tall, less than 1/4 wave ground radials and less than 1/2 wave
high.) A full length dipole is probably a challenge.

That being said, I operate mobile HF mostly. The car body is
generally a poor, but raised ground plane. On 40 and up,
communications are competitive enough to make contacts and communicate
during normal open band hours (give or take SW Broadcast stations.)
Because of power restrictions, 60 Meters works well mobile as
competition is restricted to ERP 50 watts as radiated from a dipole
antenna. 75/80 Meters is tough due to band conditions and antenna
size in wavelengths and the number of high power stations on the air.

Your ground plane antenna whether on the ground or in the air will
likely be very short. Even though its height and the length of the
ground radials (raised or on the ground) will be longer, think of the
effect of the mobile. Even though it has a shortened ground radial
system, it does work. If you can match the antenna, you can probably
work with it.

My experience is that the better the ground and the longer the
vertical element (within limitations), the better the antenna works. I
doubt there is much data reflecting various lengths of shortened
ground radials as there could be too many variations. However, there
is a manufacturer who has a vertical trap-multiband antenna that uses
one tuned ground radial for each band made up of helical wire and/or a
loading coil.

If you can't make a full 1/4 wave vertical, then do your best to make
it as tall as possible, as many, and as long radials as you can, or
make the antenna as high as you can with four radials as long as you
can, maybe loaded by helical or loading coil windings.

I hope this helps
Buck
N4PGW

--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."