On Wed, 6 Apr 2005 23:19:21 -0400, "Tom Holden"
wrote:

"Tebojockey" wrote in message
.. .

Well, our Telefunken curtain arrays have a typical gain of 20-23 dB.

TeleSource has just installed two TCI (Technology for Communications
International) 611VS curtains at 270 and 305 degrees for the low band
(6-12 MHz) here on Tinian. 3db azimuthal beamwidth is variable between
20-36 degrees, and they are vertically slewable in 4x4 and 4x6 mode.
Gain is between 16.6 to 24.1 dBi, and tower height is about 470 feet.

I would daresay if a 3-5 degree beamwidth had ever been made, it is
probably experimental. The physical size makes it prohibitively
expensive as well as mechanically improbable.

Al in CNMI
IBB Station engineer (contract)

Al, impressive sounding array.

I think you mean the 3-5 degree HF array could only have been scale modelled
at much higher frequencies.

The largest dish antenna is the Arecibo radio telescope at 305 meter (1000')
diameter http://www.naic.edu/public/the_telescope.htm. That could give a 5
degree or better beamwidth above 13-15 MHz if it had a suitable antenna at
the focal point. I don't know what its lowest frequency of operation might
be but this page http://www.naic.edu/techinfo/prcz/prczinfo.htm indicates
that 13.36 - 13.41 MHz is protected for radio astronomy. It's possible that
its original use for radar back scatter studies of the Ionosphere under the
DoD may have had it transmitting near the 20 meter band! With 5 degree
beamwidth pointing straight up, it would take a lot of hops to make any
decent terrestrial DX!

Tom


Hey Tom,

Nice to hear from you. I agree with your observations, but the
problem with what you describe is the angle of incidence/angle of
reflection.

As you point out, the hops required would probably decimate the signal
before it reached the target area. Shortwave requires a calculation
of the takeoff angle (another term for incidence/reflection) so that
the optimal signal arrives in the target area.

If we could tilt Arecibo's antenna up on a 45 degree angle, it might
have possibilities! Do we have anough men and kegs of beer to give it
a whirl? LOL

73

Al in CNMI

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