Hi Andy,
Very interesting idea. Many years ago I did read somwhere an article about
horizontal dipoles used in the desert that were just laying on the sand.
But I cannot remember where I did read it nor what frequecies were involved.
Since the polarization will be horizontal the antenna should work better
the poorer the ground is. Assuming that even on the poorest ground the
'virtual mirror' will be only a fraction of the wavelength these antenna
will radiate at rather high angles compared to the 'traditional' antennas.
This fact and the horizontal polarization make me believe that it will be
no good for surface wave propagation (for that reason probably the
'commercials' never tried it), but it might be a good sky wave launcher.
Only way to find out if (and how) it works is to try it ...
73, Rik ON7YD
At 11:31 18/01/01 -0000, G4JNT wrote:
A new subject now .....
Someone must have already tried this, but how effective would a (say)
100m long dipole laid down a chalk hill be ?
Isn't limestone also the same material as chalk, Are there any CREG
members reading this who know about conductivity of rocks?
Chalk is a very poor conductor, even when wet. A 4m earthing rod
driven into the top of Portsdown Hill on the South coast of the UK in an
attempt to make an RF ground measured 120 ohms to mains Earth - attempt
abandoned in favour of a dipole !
There are plenty of chalk hills of this sort of height, and the amount
of wire needed - 500m perhaps - means the radiation resistance will rise
to an acceptable figure to reduce copper loss.
Andy G4JNT
|
