[CS-FSLUG] Bigger antenna

[Bradly McConnell]

On 3/4/06, Nathan T. <celerate at gmail.com> wrote:

> Why is the length of the antenna half the wavelength? How does
> shortening or lengthening it affect it? Does the length of the antenna
> allow the router to pick up computers further away or does that
> require those computers to have better antennas?
>
Antennae will typically be either 1/2 wave length, or 1/4 wave length
with a ground plane.  This has to do with the electrical properties of
a conductor (such as the antenna).  I can pass along a document that
details (quite in depth antenna theory and wave propagation.)

> I've heard of wireless amplifiers, obviously they increase the range
> of the router, but if a computer was further away, would that also
> increase the router's ability to pick up on that signal?

If it is simply an amplifier, then you will be subject to the
limitation of the distant end, whereas the "amplifier" is actually a
repeater, it will work for both the router and the client.

> How many computers, or traffic do you think my router, a 4-port +
> 802.11a/b/g D-Link DI-524 could handle?

In theory, you are really only limited by the IPs and subnet mask
used, but be aware that the wireless connectivity will not be a
dedicated 11 or 54 Mbps (minus protocol overhead) to each of the
client side devices.  It only takes one slow device to bring the
network to a crawl.

> Is there some kind of regulation that would limit the size of the
> antenna I can use? Obviously I'm not talking about a 60 foot antenna
> here, more likely something no bigger than 5 metres high on the roof
> of a house, maybe even smaller if I can get reasonable range .

Again, you are constrained by the actual properties of the waves
produced by the equipment - a bigger antenna does not result in a
bigger signal or better reception.  The antenna has to match the
frequency being used.

> How about regulations on how much power I can use in the antenna
> without requiring any kind of licenses or permits (in Canada)?

For the above two items, I would dig around an find out if there is an
agency/ministry equivalent to our Federal Communication Commission in
the US.

> Obviously you know I'm going to be messing around with this stuff
> sooner or later. But not for a few years yet. I'm now thinking of
> getting into some networking related technical courses after high
> school and then I'll have my fun.

What is the actual goal of this kind of project?  Residential wireless
equipment isn't really designed for these kind of situations, but
there is plenty of commercial gear, but it gets very expensive very
quickly.

For what it's worth - I am not a HAM radio type, but I do deal with RF
communications for long haul, LOS, and SATCOM applications.  Let me
know if you (or anyone else on the list for that matter) wants a copy
of the reference mentioned above.

Brad