<OT> How many Boxen?

[David A. Bandel]

On Wed, 29 May 2002 17:29:20 -0500
begin  Michael Hipp <MHipp at redmule.com> spewed forth:

> This might be the way to scatter recording webcams around the farm.
> 
> What kind of amp and high gain antennas are you using? Does antenna
> height matter as long as it is line-of-sight?

I'm using a 500mW amp over 100' of LMR-400 w/ a 8dbi omni, pointing at it
I'm using mostly 21 and 24dbi grids or 18dbi flat panels, but at the same
distances I've used 3dbi extenders and gotten good signal (ranges up to
about 3mi/5km).  With two 24dbi grids using 500mW amps you can transmit
and receive up to 30 mi (50km).  Here in Panama, the law allows for up to
4Watts at the antenna.  That would basically allow me to transmit between
any two points over flat terrain using 100' towers.  That's a long way.

antenna height:  OK, you're asking the right question.  An omni, while it
has a horizontal 360 degree fan, has a vertical fan of only about 22
degrees.  So an antenna 1 mile away would theoretically have to be within
100 feet vertically of a perfectly horizontal omni.  In practice, I have
yet to have vertical differences give me any great problem.  OTOH, my
antennae are deliberately over-kill.  And while you shouldn't be able (by
the book) to see the signal from an omni nearly directly below it, you
will.  Reasons: there are small lobes with vertical components, you have a
phenomenon called a ground plane, and you're just too bloody close not to
see a signal.  You'll have to look up the ground plane calculation, but
it's based on the height of the antenna to the ground.  The higher up, the
larger the ground plane.

Also remember, all this "25 degrees vertical, 45 degrees horizontal" is
designed so that you'll see a 5db signal within the cone.  But even 3db
could give you an acceptable signal (and that's well outside the cone).

Your biggest problem will be line-of-sight (LOS).  Even a tree branch with
leaves on it will pose a problems (although the signal will pass right
through clear glass).

Caution: most countries don't permit amp'd omnis.  Please check your
country's laws regarding frequencies, power output, and directionalness of
the signal beam (directionalness -- what the hell am I smoking? gotta be a
new word, I should trademark it).

Ciao,

David A. Bandel
-- 
Focus on the dream, not the competition.
		-- Nemesis Racing Team motto