Re: [OT] [Possibly] WiFi WLAN update..

["andylaurence" <andy@xxxxxxx>]

> >>That's 13,920 metres away
> >
> >Word of warning: a wireeless link over this distance *will* be
illegal.
> 
> err.. you sure?

Yup, 100mW EIRP will only get you about 2km at best.  Unless
you're
using circulators to increase receive gain whilst not increasing
transmit gain, you'll get no more than that whilst being legal.

> I really, honestly, don't understans the maths involved any more,
but I was
> under the impression that using a CE marked, UK sold WiFi Card,
the
radiated
> power should be within the legal limit using an antenna of up to
21db Gain.

I think it's about 15dB, but I'm not sure.  Anyway, each wireless
card
is different - 30mW, 50mW or 100mW AFAIK.

> It's one of the reasons I chose 19dbi antennas, max power whilst
> staying legal..

At that distance you will have to break the law.  Mind you, they
will
only take action if there is a complaint.  Also, I believe they
just
remove your wireless card, although I cannot confirm either of the
above.

> > When you say you have LOS, do you mean you can see
> > eachother, or you have radio LOS?  The two are mutually
exclusive.
> 
> I don't know about that Andy! I know that RF LOS and Visual LOS
are
> not the same thing, but they are not mutually exclusive!

Sorry, a bit too much exaggeration there!  I was just trying to
emphasise the point that visual LOS does not imply radio LOS, although
the inverse is true.

> I have some concerns about a) some trees at about 500m from me, and b)
a
> tower block at about 2 degrees off line and 6km out, which *may*
protrude
> into the fresnel zone. If the trees are a problem, they are on old
> commercial ground *cough* chainsaw *cough* the tower block is more of
a
> problem, but I think it's far enough out of line..

You'll need a new chainsaw blade for the tower ;-)

I think it'll be a suck it 'n' see job :-/

> >For perfect signal quality, you need clear space in an elliptical
area
> >between the two aerials.
> 
> Agreed, but we have a bit of gain to play with. not to mention
that
whilst
> 11Mbps would be nice, for sharing a 1Mb DSL connecion (the
ulterior
motive
> here) we really don't need that much. I would be happy to get a
2Mb
Direct
> Sequence connection going.

OK, but each obstruction will lower the maximum gain.

> >You'll need some good gain on the antennae to get that
distance,
> 
> hence, buying a commercially manfactured antenna rather than trying
some
> Pringles can hilarity. ;)

Good call!

> >but it's not impossible by any means.
> 
> Well, given Lucent are selling 25Km capable bridging gear, 14km
should be a
> walk in the park :D

Indeed it should be.

> >Is your plan to hook up two 24dB antennae and hope for the
best?
> 
> Well, we have spent quite a bit of time driving around with
Orinoco
+ Laptop
> plotting WLANs, to ensure we don't stomp over someone, getting GPS
fixes on
> almost everything taller than six storeys and trying to see if it
will fly..
> 
> but ultimately, yes.. it's a question of fire it up and see. :D

Cool, keep us posted....

> >Community (wireless) networking for Bristol
> >http://consume.andylaurence.co.uk
> 
> As an aside Andy, are you guys using all short local hops in
> Bristol, or are there any big links involved there?

At the moment?  Nothing is more than local hops.  The problem
with
Bristol is the hilly nature of the area.  My brother lives 450m
away,
but due to a hill, there's no way we could connect.  If I find
someone
who is within range of a node, then I'll do my best to connect them. 
I have a possible node on the side of a hill which overlooks much of
central and east Bristol.  Unfortunately, I know of nopeople in
central or east Bristol :-/

There's going to be an article in .net magazine soon which I hope will
drum up more support from those people not so technically minded. 
Before then, I hope to have the standard hardware up and running.

Andy



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