My eight years older brother was an MP over fifty years ago.I have every
right in the World to read alt.military.police news group and post there
any time I feel like it.I guess you have a problem with that too,eh?
cuhulin

George Ashley,and then my eight years older brother got in Helicopter
Maintnance.He was a Helicopter Mechanic at Vung Tau,Vietnam in 1964 (his
second Tour of Duty in Vietnam following a year in Germany) the same
year I was in Vietnam too,in 1964.YOU are the DUMBIST SON OF A
BITCH!!!!! IN THE WORLD!!!!
cuhulin

"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)

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
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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

"Dale Parfitt" wrote:

A rough esrtimate tells me an array of 4000-8000 1 wavelength dipoles
could achieve this.

Heh. I'd like to see the phasing harness!

Not likely. Such an array would be about twenty wavelengths wide (and still
have reasonable side lobes).
It is improbable that one could keep the required elements' current close
enough in phase to be able to realize a 2.5 degree beamwidth. Too
expensive. If used on a path that is longer than something like 10Mm, the
narrow beam will occasionally miss the target (unless one adds skewing,
which would be expensive in this case).
In other words, a SW broadcast system would not want such an antenna.
Less expensive and more reliable to buy a larger transmitter.

Why do you ask?

Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"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.

"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

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