Re: Re: Radio networking...

["Ian Lowe" <ian@xxxxxxx>]

The thing to bear in mind is... those fancy antennae are not that
expensive,
with www.fab-corp.com (for instance) supplying pretty high gain parabolics
for around 50 Dollars. (for reference, it cost us about £130 landed for a
pair of 21dbi parabolics from fab-corp)

These high gain antenna do more than boost your output power: they boost
your sensitivity enormously, and the trick to legal long range links seems
to be to use kit that allows you to drop the output power level to bring it
inside the limits (like the netgear APs), whilst using a very high gain
antenna to boost the receive sensitivity.

My own long range link was hampered both by SWMBO approval at the remote
end
and by a bloody big tower block protruding into the otherwise unobstructed
fresnel zone : but I found this link helpful..

http://wireless.gumph.org/articles/longrangelink.html

We had a 4Km test across a lake working trivially at 11Mbps, in fact, the
signal was so strong, that the receiver was saturated on the main beam, we
had to turn one of the antennae about 10 degrees off-beam to hit a side
lobe
instead..

If the legal issues are not so significant (if, for instance, your area is
very rural) I'd imagine that 1.9km with the right antennae, you could
happily punch through concrete walls  ;)

Ian.

----- Original Message -----
From: "james_dunn67" <james.dunn@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Tuesday, May 06, 2003 10:33 PM
Subject: [ukha_d] Re: Radio networking...


> Brian,
>
> Since it looks like you're doing this for a public body, you should
> be aware that you need to keep within 100mW (20dBm) EIRP (effective
> isotropic radiant power).
>
> To reach 2km with a good signal level, you are very likely going to
> break the UK maximum permited RF power levels unless you buy some
> very fancy high gain aerials.
>
> See:
>
> http://www.cisco.com/warp/public/102/wlan/faq-hardware-us-calc.xls
>
> For a good design reference.  (Don't forget to set the regulatory
> domain to ETSI)
>
> Other manufacturers may have slightly more sensitive radio kit than
> Cisco to improve the range but I doubt if they'll be significantly
> different.
>
> Sorry to be a spoil sport.
>
> Regards,
>
> James