On Fri, 14 May 2004 20:44:40 -0400, Dave Holford
wrote:

Interesting question. I have seen the dipoles used for HF communications
with transatlantic air traffic from Gander, or at least one site which
IIRC was the receiver site. Since this, and similar installations around
the world, need reliable communications at a number of frequencies to
provide coverage over a wide area and while they may have a kilowatt or
so for transmit; on receive they are working with a station whose
transmitter is unlikely to exceed 400W PEP and whose antenna is at best
a poor compromise since the days of aircraft wire antennas are long
gone.

I don't know about other sites, but Gander certainly used to have a
number of just plain old dipoles; and I have seen other simple dipoles
at several other airports and airline installations so one would expect
a fair amount of operational data to have been gathered over the years.

I worked at a station in Alaska that had a big antenna farm. The
station was designed to communicate with aircraft over distances from
zero to thousands of miles. We had very few limitations over what we
could do or build with unlimited space, and had two rhombic's for
communicating with two flights that took the same track every day.
Communication was mostly CW five letter group encryption. The
transmitters and receivers were separated by 20 miles or so.

The operators could choose which transmitter/antenna combination gave
them the best performance. The dipoles seemed to be the preferred
antenna. The rhombic's (the king of HF antennas) were seldom used,
probably because of the radiation pattern. The antenna is the most
unpredictable part of any installation.

I was the guy that tried to neutralize the big triodes, so you know
that was a while ago. (1950's). The globe was about the size of a
volleyball.

Ron, W1WBV