View Single Post
  #6   Report Post  
Old September 11th 08, 04:05 AM posted to rec.radio.amateur.antenna
[email protected] jimp@specsol.spam.sux.com is offline
external usenet poster
 
First recorded activity by RadioBanter: Jun 2006
Posts: 1,898
Default Light,Lazers and HF

Art Unwin wrote:
On Sep 10, 8:45?pm, wrote:
Art Unwin wrote:
What is the main factor that prevents HF radiation from focussing
for extra gain?


Money.

If you can afford to build a 20m parabola about 2,000 feet in diameter
and the place to mount it, you'll get lots of gain.

--
Jim Pennino

Remove .spam.sux to reply.


Then are you saying it is the antenna size that is the main factor?.


Of course.

Everyone knows the gain of a parabola is directly proportional to
the size in wavelengths, or:

G=10*log k(pi*D/L)^2

Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas,
D is the diameter, and L is the wavelength (wavelength and diameter
in the same units.

So a 2,000 foot parabola on 20m would have just about 58db gain.

--
Jim Pennino

Remove .spam.sux to reply.