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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
I would find the central point and place broadcast point there and at the end of that one range place 2 at the other points to max. range and give full coverage. Nice idea. I am working on something like that for my wine cellar.
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.
This is our amateur radio repeater that uses VoIP to link to other repeaters around the world. The link is 802.11b
Here is the AP that provides access.
Nothing special to do a 1000' link. Just a parabolic grid antenna on the client side.
Here are some parabolic grid antennas.
--fatboy
Cantennas are the wrong way to go, as their propagation pattern approximates linear, like the yagi designs. What you want is an omni, sometimes called marine, antenna that will spread signal in a plane. If you're in a greenhouse, I'm assuming you don't want strong signal going up or down, but horizontal in the plane of people walking around. Here's an example of one I grabbed from Google: radiolabs omni antenna For about another $30 you can pick up pigtails on eBay that let you attach these to the usual netgear/buffalo/d-link/linksys/etc. accesspoints. You can place them for effective 10Mbit coverage about one for every 2 acres assuming clean line of sight to the antennas and no major obstacles. Note that vegetation would definitely impact signal propagation in the 5.4ghz band.
http://tinyurl.com/4ny52
Yeah. The FCC typically just responds to complaints. As long as you don't paint a picture of Janet Jackson's nipple on the antenna you should be fine.
blog
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
You'd be suprised the kind complaint they respond to. My house used to have a very large antenna for TV(35 foot I think) because we were on the dark side of a mountain and couldn't recieve a signal from NYC. We also had a special motorized/pointable CB antenna. The guy next door, instead looking at the mountain and thinking, "hey the only reason they can a signal is because they have a giant antenna" thinks "hey they are plotting against me, and blocking my signal"
The FCC actually came and did tests, said that was silly and went home.
=1000101
Or you can search froogle for them
"2.4 ghz parabolic antenna"
Lowest price is around 33$ for a 15dbi gain. 50$ is about right for a 24dbi gain. Though a parabolic is only going to be truly handy for sight to sight. They do have low cost omni directional antennas. This is difficult to advise without knowing the layout.
ie, possibly sight to sight parabolic for the backbone link and then omni's distributed throughout.
If you are really worried about distance, just dig up a router that can be tweaked for a bit more output power.
Now, if completely unsure of what your needs are, here is a handy calculator to help you figure your distance needs out.
http://www.signull.com/fsc.php
For the uninformed, cable loss is going to be calculated by the amount of signal loss expected when using some portion of cable from the transciever to the antenna. It should be expressed quite clearly on type of cable you are going to be using.
There are also some common models output numbers listed there as well.
That really sums up everything. It should be quite cost effective to implement a few antennas and a cheap 802.11b setup.
"You should always go to other people's funerals; otherwise, they won't come to yours." -- Yogi Berra
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!
A lot of those wireless cable antenna are actually in the 2.5ghz range.
Still, they will work just fine, with some gain loss...
Here is a smaller article on the matter... to adapt one. (kinda helpful if you really really don't know what you are doing)
http://www.qsl.net/n9zia/wireless/page04.html
"You should always go to other people's funerals; otherwise, they won't come to yours." -- Yogi Berra
A friend pointed the site out to me about a week before it hit slashdot, so by the time the original story broke here, I had built one.
Long story short. They work really well. I've pwned every wireless access point within a 3Km radius of my house. Free Internet anyone? :-)
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