[FADCA] 802.11g Experment

[Chuck Hast]

On 12/6/05, Doug Christ <kn4yt at yahoo.com> wrote:
> I, along with our county IT person, have been conducting some 802.11g
> experiments here in DeSoto County. The driving force behind the experiment
> is internet connectivity or lack there of after a major disaster. Hurricane
> Charley left most of our county without commercial power for up to two
> weeks. With no power, most end offices or other telephone devices that do
> not have long term power back ups in place die. In other words, you loose
> dial tone and data networks.
>
> My EOC is right across the street from the main central office that services
> DeSoto County. We never lost telephone service and our T-1 lines remained on
> the air. We assumed that with the proper equipment, we could shoot a signal
> back to the EOC from field locations and provide email and internet to
> mobile command sights.
>
> I do have a license for the 4.9 GHz public safety spectrum but the equipment
> is very expensive. Our IT person, Leonard, discovered that you can install a
> different firmware into a Linksys wireless router, that you can configure
> the router into gateways and repeaters. The firmware we use is
> Talisman/Basic 1.1 which is Linux based. For security, we have set the
> router for MAC address verification, we turned off the SID broadcast and
> require a password for access.
>
> 2.4 GHz requires line of sight so I needed to install an outside antenna. I
> installed a 15 DB gain vertical on top of my EOC. The antenna is
> approximately 80 feet off the ground and provides a decent line of sight for
> many blocks around. I installed an antenna adapter to convert the TNC
> connecter to a N connector and installed  polyphaser lightening protection.
> I only used about 25 feet of low loss coax as I have a equipment room
> located in the top of the building near the base of my tower.
>
> Results were surprising. We can connect to the router using the wireless
> connection built into a laptop for about four blocks as long as you could
> see the building..In certain cases, we could stretch the connection to about
> 1/2 a mile. If you set a wireless router up as a gateway, in other words,
> connect your computer to the router and use it as your RF source, range
> doubles if not triples using the standard rubber duckies that come with the
> router. The farthest we have connected using the gateway approach is 4 1/2
> miles. We drove out to the landfill and parked on top of the hill which is
> approximately 65 feet high. This puts us above the tree line and we have a
> clear line of sight back to my office. It worked great and I believe the
> connection speed was 11 MB.
>
> I cannot help but wonder if we can use these routers for a  high-speed
> backbone for our network. Heck, why not local access as well? You mount the
> dish on the tower, install the router in a weather proof container and run
> the power to the unit up the cat 5 cable. Some of the web pages I have read,
> claim ranges of 30 miles when used with a parabolic dish.

Doug, this has been one of the reasons that I have been pushing us all
to move our switches to Linux, in this respect we have been a bit busy on
other things, but a combination of a bit of ham scrounging and ingenuity
and we can use these things to build those high speed links and accesses
as you can see from your testing, you do not have to limit your operations to
just a few tens or hundreds of feet from the site, you can with a bit of work on
both ends go quit a distance, and the "digi" needed to extend that distance
is not that expensive a device either, or for that much a full fledged switch.


--
Chuck Hast
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going
out and having to identify your bits and pieces in the midst of torn
and twisted metal."