need your advice on wireless

[David Bandel]

On 6/18/07, Vu Pham <vu at sivell.com> wrote:
> On Thu, 2007-06-14 at 08:34 -0500, David Bandel wrote:
> > On 6/14/07, Vu Pham <vu at sivell.com> wrote:
> > > I have built some wireless ( 802.11a/b/g) networks but they are all in
> > > house.
> > >
> > > Now I get involved into a project that requires me to cover a yard. The
> > > size of the yard is about 1500'x 1000'.
> >
> > Approx the size of a football stadium  This is easier than inside a
> > house -- should be no serious obstructions to block the signal. You
> > may need an 8dbi omni or small sector antenna to increase signal
> > coverage.   Just don't let water get into any antenna connectors.
> >
> > The biggest secret about wireless communication is not how much power
> > you put out (how loud you shout), but how good you can hear the signal
> > (how good your ears -- antennae -- are).  Most folks get this
> > backwards.
>
> David,
>
> I look at the spec of the high-gain omni antenna and it shows they have
> the beam width around 38 oV. This means the area right below the antenna
> has no coverage. Is it ok to have a smaller antenna below the high-gain
> one with different channel ( I am going to use 802.11g ) in order to
> cover that area ?
>

Won't be necessary.  The beam width you see is the 3db envelope.  That
means as you leave that vertical range, you'll still see signal, but
it will not be full strength.  As you move above or below, signal
strength drops off rapidly.  So if you have an antenna 15 miles away
at sea level and the omni is on a 3km high mountain, you might need to
tilt the omni.

However, anything within the ground plane of the antenna (below that
antenna out to a certain distance, that distance determined by the
height of the antenna above the ground) will receive good signal.

You should not need a second antenna.

Ciao,

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