"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