[SunRescue] Suburban Wireless?

[James Sharp]

> Some acces points advertise up to 250 meter range, but with the standard
> antennae you are lucky to get 100 meters,and more like 50 with obstructions.
> It's illegal to amplify the signal beyond a certain point, where it could
> "cause undue interference" which basically means scrambling your neighbors
> cordless phones etc... etc... so your best bet here is good antennae design.

They're certified under FCC part 15, which means a) It cannot cause
interference and b) Must accept any interference.  But yes, good antenna
design is definitely a must.  You can overcome a lot of the problems
caused by lack of transmitter/receiver horsepower with antenna gain.


> With proper antennae selection, good connections, and a good low loss feed
> line I figure you could put up a good Omni-directional rig with 1/4 - 1/2
> mile range even through the 80 ft trees and other hazards.

Unless you're going to put the access point within a few feet of the
antenna, you'll need to end up using some rather expensive hardline to
make the run.  Even good quality Belden 9913 has atrocious loss at 2.4Ghz.

>
> The best way I can think of is to have each house with their own access
> point in the attic, with as short a feed line as possible running to an
> external antennae. Then put each of the access points on the same WLAN with
> the same encryption yadda yadda
>
> It is possible to have the system inside the roof but 2.4 ghz signals are
> SEVERLY attenuated by common houshold building materials so it would reduce
> your range a lot.
>
> As to antennae design I'd go for either a standard vertical, or maybe a
> circularly polarized (hoop, cylinder, or box shaped) antennae.
>
> I've never tried using a circularly polarized rig with very high frequencies
> before so I'm not sure if there would be a benefit to them or not, but at
> lower frequencies they can give you a radiation pattern that reduces
> environmental signal attenuation.

Loop-shaped (unless they're a helix) antennas aren't circularly polarized.
They're horizontal or vertical depending on the orientation of the feed
point.  Here you could use an 18-20 element loop yagi, which would end up
being maybe 2-3 feet long and have 12-18db of gain (I forget the actual
numbers).

Use the yagi at the remote node sides, and then use a coaxial collinear
antenna at the central point...they provide excellent omnidirectional
gain.

Adding circular polarization would only make building decent omni-antennas
difficult at best...and really wouldn't gain you anything.  CP really only
gains you anything (IMHO) when you shoot through the ionosphere and have
to deal with Faraday Rotation.