Max Power wrote in message
...
Has anyone ever designed a SW transmission system using curtain arrays
that
has a beamwidth of 2.5 to 5 degrees?
Most standard curtain arrays [HR 4/4/1 to 12/6/1] have 15 to 30 degrees of
beamwidth.

Talk about the curtain array... that brings to mind a somewhat recent class
I took, that of all students attending, there was the daughter of a VOA
engineer responsible for rebuilding a number of stations; she was in my
study group and what a nitwit!

I played dumb and never let on I knew anything about shortwave broadcast
stations or the pecuilar circumstances and delicate political situation
regarding one of her father's constructions.

RG

"Max Power" wrote in message
...
Has anyone ever designed a SW transmission system using curtain arrays
that has a beamwidth of 2.5 to 5 degrees?
Most standard curtain arrays [HR 4/4/1 to 12/6/1] have 15 to 30 degrees of
beamwidth.

It's gonna be big! A 3 meter diameter dish at 4 GHz has a beanwidth of 1.75
degrees. Scale that to 4 MHz and it will need a diameter of 3 kilometers.
For 5 degree beamwidth, probably about 1 kilometer diameter for 4 MHz, and
400 meter diameter at 10 MHz. An array will have similar dimensions for
similar results.

Tom

"Tom Holden" wrote in message
.. .
"Max Power" wrote in message
...
Has anyone ever designed a SW transmission system using curtain arrays
that has a beamwidth of 2.5 to 5 degrees?
Most standard curtain arrays [HR 4/4/1 to 12/6/1] have 15 to 30 degrees
of
beamwidth.

It's gonna be big! A 3 meter diameter dish at 4 GHz has a beanwidth of
1.75
degrees. Scale that to 4 MHz and it will need a diameter of 3 kilometers.
For 5 degree beamwidth, probably about 1 kilometer diameter for 4 MHz, and
400 meter diameter at 10 MHz. An array will have similar dimensions for
similar results.

Tom

An excellent analogy Tom. Narrower beamwidths come about as a result of
increased gain. Increased gain comes from larger arrays.
Those kinds of beamwidths are practical at microwave freqs, not HF.
The gain of the 1M dish (2.5 degree conical beamwidth) at 4 GHz is around
40dBi. A rough esrtimate tells me an array of 4000-8000 1 wavelength dipoles
could achieve this.
Then again, I could be wrong.
Dale W4OP

On Wed, 06 Apr 2005 02:52:41 GMT, "Dale Parfitt"
wrote:


"Tom Holden" wrote in message
. ..
"Max Power" wrote in message
...
Has anyone ever designed a SW transmission system using curtain arrays
that has a beamwidth of 2.5 to 5 degrees?
Most standard curtain arrays [HR 4/4/1 to 12/6/1] have 15 to 30 degrees
of
beamwidth.

It's gonna be big! A 3 meter diameter dish at 4 GHz has a beanwidth of
1.75
degrees. Scale that to 4 MHz and it will need a diameter of 3 kilometers.
For 5 degree beamwidth, probably about 1 kilometer diameter for 4 MHz, and
400 meter diameter at 10 MHz. An array will have similar dimensions for
similar results.

Tom

An excellent analogy Tom. Narrower beamwidths come about as a result of
increased gain. Increased gain comes from larger arrays.
Those kinds of beamwidths are practical at microwave freqs, not HF.
The gain of the 1M dish (2.5 degree conical beamwidth) at 4 GHz is around
40dBi. A rough esrtimate tells me an array of 4000-8000 1 wavelength dipoles
could achieve this.
Then again, I could be wrong.
Dale W4OP


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)

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I sort of know a guy in Hattiesburg,Mississippi.He is about 73 years old
and he was at Kagnew Station in Africa. www.kagnewstation.com He
worked in decyphering radio signals at Kagnew Station,U.S.Army.I bet
they had a really good radio and antenna setup there.
cuhulin

"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

Tom Holden wrote:

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

Has anyone here ever seen a real curtain antenna while standing
underneath? I visited the old VOA plant in Mason, Ohio "Bethany" in the
late '60s and got the full tour with my high school's ham radio club.
Today its just another golf course for Cincinnati.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

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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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)

I wonder if shortwave broadcast antennas have been used for
signals/communications intelligence?

RG

On Thu, 07 Apr 2005 15:19:29 GMT, "RadioGuy"
wrote:

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)

I wonder if shortwave broadcast antennas have been used for
signals/communications intelligence?

RG


Back in the old days of the ASA, we had a General Dynamics FLR-9
antenna at most field stations. It was about 2km in diameter with
vertical antennas for every degree.

In germany, late at night, we would roll the old R-390A up on
mediumwave and listen to ball games from New York.

You can see a picture of one on the home page at www.usafsa.org which
is Field Station Augsburg's home page.

ASA Lives!

Al in CNMI

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