I suspect such an antenna is HRS 12 / 6 / 1 or possibly HRS 18 / 6 / 1,
using horizontally placed dipoles as is typical with HRS antennas.

See:
CBC.am/HR.htm
-- for a guide to HR antenna types.

I understand that in Siberia that there is such an HF curtain array that
has
26dbi gain.
I guess is operates 9 mhz ... 21 mhz bands, but information on former
USSR
curtain array antennas in Siberia is quite limited as GOSTELCOM (the
Russian
Telecom PTT) that runs these sites is mum on the technology.

However, the necessary size and beam width characteristics can be
calculated
fairly directly.


The most amazing thing is that there are MW transmission sites in Russia
with 26 dbi gain -- and designed for skywave reception.


If you start with one halfwave dipole, you get 2.14 dBi gain.

If you double the number of these antennas, with suitable spacing
to ensure their capture areas don't overlap, you can increase the gain
by a maximum of 3 dB, with 2.5 being a common case due to losses in
the system.

If we are shooting for 26 dBi, you need 26 - 2.14 = 23.86 dB gain

Doing this would require putting up 243 of these dipole antennas.


If instead, you used an array of yagi antennas, each with 8 dBi gain
(fairly large, but probably possible), you would 'only' need 63 of them.


mikehack wrote:
With enough radiators arranged in the right order, 26 dbi gain is easily
obtained -- and the need for extremely high power transmitters is
reduced.
Directional gain antenna systems make modern broadcasting possible...


Antennas with that much gain are not particularly useful for
broadcasting,
since the beamwidth is so narrow. Lining up a row of vertical halfwave
dipoles
would get a pattern in elevation similar to a single dipole, and would get
all
the gain by squeezing the azimuthal beamwidth down to a degree or two.

My calculations show that 26 dBi has a symmetrical beamwidth pattern
of about 10 degrees. Any increase in beamwidth (such as arrays of side
by side antennas would have) would require a reduction in the azimuthal
beamwidth.

There are folks who are really good at this -- however, if you want
their
services, you probably would have to pay them.


So, Mike, what are these postings about? They didn't seem to be a
response
to postings in the newsgroup where I found them.