[FADCA] 802.11g Experment

[Doug Christ]

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/KN4YT