Jack Twilley wrote:

So who actually has the space and resources to set up an ideal
horizontal dipole on HF with the full length and height as specified
in all the formulas? Wouldn't it be cheaper and easier to set up a
vertical if you could install something that high off the ground?

The only thing I've seen personally that looks like it meets the ideal
is a small station tucked into the northeast cloverleaf of an exit off
Interstate 93 near Boston, MA, and the station appeared to be a marker
for Logan. Anyone have any personal, real-life experience with a
full-size, full-height HF dipole? Is it worth the cost?

Jack.
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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.

It seems to me that most of the professional vertical installations I
have seen are those which tend to require operation at multiple
frequencies with a single antenna - i.e. shipboard and military
installations, although there used to be quite a lot of verticals at
Coast Guard stations for the 2 MHz band.

Re. the installation at Logan; I would be inclined to believe that what
you are seeing is a top loaded "T" configuration for a Low Frequency
(200 - 400kHz) Non-Directional-Beacon.

Dave