On Thu, 25 Sep 2003 22:17:35 +0800, "Richard Hosking"
wrote:

If you are working at low frequencies, I have seen an idea using a very long
wire (say 4-5 wavelengths) at a low height above ground (say about 6 feet).
The antenna can be directive in it's long axis. It can help to reduce QRM
from a particular direction. Of course you need a fair bit of room...

Richard, back in the '80s we set up several of these for the SES for
poin-to-point operation from Perth to Carnarvon and Port Hedland.
They offer a huge number of positives for p2p and point-to-area.

There is a CCIR publication "Handbook on High-Frequency Directional
Antennae" published in 1966 which is very good background for anyone
into this area.

More specifically, there is a very specialised report from the
Communications Research Centre in Ottawa titled "Beverage Antennas for
HF Communications, Direction Finding and Over-the horizon Radars" (CRC
Report #1282 - August 1976). This gives in vol2 all sorts of
parameters for HF beverage-type antennae. Gain, takeoff angle,
beamwidth, impedance etc as a function of ground type/condition, wire
length, wire height above ground etc. One VERY good read.

Both are decades old, but the laws of physics and iononspheric
behaviour are pretty stable ;-)