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Wide Area Wireless on a Shoestring Budget?
wkytechhead asks: "My father owns a greenhouse operation that covers a few dozen acres. He has a number of greenhouses some up to 1000' plus apart that he would like to network. Currently he is using a HomePNA based network via regular RJ12. He has decided that he would like to go at least partially wireless. Some consideration has been given to using the backbone with fiber convertors, but he would really like to do full wireless. I have checked into homemade and commercial 'Cantennas' but I am not sure if they are worth the money. How would my fellow geeks go about wirelessly networking a large outdoor area for as cheap as possible?"
You should check out these antennas from HyperLink Technologies. For outdoor applications these should work very well for you.
Some golf courses and other large areas use remote-DSL for such links. Maybe that would apply to him? Many cisco DSL modems can be operated in server mode, only downside is you must run RJ12 separately to each location.
Otherwise, run ethernet?
if you are going to go wireless, get some good APs and sector antennas, or alternately setup a bunch of repeater stations that use different channels to avoid interference.
--IronHelix
minidishes (commonly used in the UK for digital satellite television) can be easily adapted to use a WiFi signal boosters. They're highly directiuonal of course, but ranges of 2 or more kilometers LOS are not unknown. Plus, no boosting equipment is required, just a modification to the antenna.
For outdoors, I think your SOL, but for inside the greenhouses, investigate something called "leaxy coax." It's basically a coaxial cable with little to no shielding, and a couple of companies have recently made it usuable with 802.11b/g.
Wire cheap antennas to cows.
:)
Problem solved
http://www.seattlewireless.net/index.cgi/AntennaHo wTo
Is a WiFi antenna howto and I build the can-waveguide out of two tomato sauce cans with an N connector. It totaled to about 5 bucks worth of parts and works very well. The tuning for it though might be off and I hand redid with a sheet metal snipper.
Can't get much cheaper. http://www.faqs.org/rfcs/rfc1149.html
The first question you have to ask yourself is what you want to get out of the network. Do you want full roaming capabilities, or do you want localized points of presence in every greenhouse? Are you wanting to implement VoIP? Network aware control and monitoring systems?
If you are looking for a setup like what I had (points of presence in every greenhouse), all you need are some cheap(ish) base stations for the endpoints, and a kick ass 24dB omnidirectional antenna for the master base station at the head office. Build small networks at each pop and bango. If you want roaming in a few areas, throw in a small consumer wireless base stations and hook it up to the pop.
If, however, you are looking at using the network for business critical voice services or control and monitoring systems, then you had better look seriously at fiber (fiber ring preferably). You never know when some bird lays a massive shit on the antenna. Wireless is simply not as reliable as wired.
Feed the need: Digitaladdiction.net
Use a link budget calculator. (The link is one I just found with google).
Basically, you need a certain signal to noise ratio for a digital radio connection to work at all at its lowest speed. Increased signal to noise ratios get you more speed and some margin of reliability.
Signal decreases with the square of the distance. If you double the distance you'll have one quarter the signal, or 6db less (decibels are logarithmic - 3db is a ratio of 2, 10db is a ratio of 10). So, everything else being equal, you'd need 6db more gain on the antenna at either end to get the same results.
For your particular scenario you'd probably be fine with just a couple cantennas or other moderate-gain antennas.
One thing to watch out for when shooting through trees is that they may not have leaves now but they will in a few months!