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Wireless Networking Equipment

The first thing you need to do when deciding what kind of equipment you need for this stuff, is what is the purpose of your wireless networking.  Are you trying to link up 2 places?  Trying to make a hot spot?  Trying to link up multiple buildings that are a long ways away?


There are 2 types of antennas. . .  omni-directional and directional.  Omni-directional antennas have 360 coverage [or almost].  Directional antennas only go one direction, and have varying beam widths and areas they cover.  Why would you use a directional antenna over an omni?  Paths of signals only covering a smaller beam width are less susceptible to noise, and tend to go really far.  Also, directional antennas are usually cheaper.  Basically, if your signal needs to go to more than one place, you should have an omni directional antenna.  If you're going the directional route, buy or build a yagi.  [Rediculously directional]

The next factor in choosing an antenna, is how much gain do you need?  Gain is measured in Decibles [dB].  Your signal doubles in strength every 3 dB, so if you're putting out 32mW and you have a 6 dB gain antenna, you will be outputting 128mW.  Likewise, if you have a cable that attenuates 3 dB after an initial output of 32mW, you will be outputting 16mW at the end of the cable.  So how much gain do you really need?  There are many things that affect a signal, so it's hard to say.  From past experiences, I can tell you that 15 dB gain antennas on both sides carry a 1 megabit link about 8 miles.  However, this is with a clear line of site, perfect environmental conditions, and perfect ground topology.  Also note that both of these antennas are omni-directional.  I've heard a few places that a couple Pringles cans with 12dB gain, and initial power for 32mW can get 11megabit at over 10 miles away.  Your best bet is to get the highest gain you can, but there is rarely a need for anything greater than 16 or 18 dB.  Anything past that, and you start running into safety issues [2.4 GHz waves are used to cook your food in microwaves, and they will melt your eyes with long term exposure], and problems with cards not being able to push that much power. 


Need a PCMCIA card?  Get an Orinoco Gold.  Best you can buy, well worth the price, and they have a nifty external antenna connector on them already.

Need a PCI or ISA card?  Don't ask me, I haven't used any, but what I'd do is get one of those PCI to PCMCIA adaptor thingys, and plug an Orinoco Gold into it. 

AP's and Bridges?  The Linksys WET11 Ethernet Bridge is excellent.  It's also extremely fast.  As for access points, I'd probably also recommend linksys, unless you are an ISP or something, and have some money to throw around.  I haven't tried Cisco's stuff, but I see no point in it.  You'd just be buying a name with them.  3Com's equipment is also nice, and is usually affordable.

Cables, Connectors, and Other Doo-hickies

First off, you'll probably need a pigtail.  this is nothing but a short little adapter cable that plugs into your 802.11 card, or other device, and has an N type connector on the other end.  [It doesn't have to be type N, but that's the standard, so you might as well use it].  Next thing you need is a chunk of coax.  Get LMR-400 if you can.  Note, that it sometimes goes under other names.  You'll need N connectors on both ends of that coax.  Yes, you can put your own on, but sometimes it's just easier to buy a 20' section of it with the ends already on.  Keep in mind when getting coax. . . .  the shorter the cable run, the less signal loss you have.  Don't use more than you have to. 

After Setup

A few things you need to do after you get done hooking this all up.  If this stuff is outside, go to the hardware store, and invest in a roll of this rubber tape stuff made by 3m.  [Some places don't have it, but it's worth looking around for.  Normal electrical tape is not the best for waterproofing]  It's expensive, but worth it.  Wrap the stuff around all the connections that are out in the elements.  If water were to get into your connection, it'd be really really really hard on your radio, which could eventually fry the thing.

As for antenna pointing, pointing it right at the other antenna isn't always best.  Sometimes aiming right off the side depending on the radiation pattern might help your signal.  Experiment, change only one direction at a time and see if it gets any better. 

Another classic problem, is lack of a secure mounting device.  Don't attach a 50' pole to your chimney with the only braces being at the very bottom of the pole, 6" apart.  Any physicist or a person with common sense will be able to tell you that it'll fall over.  If it's on a big pole or tower, use guide wires, attached to something sturdy on the ground.  Make sure the antenna itself is very secure.  You'd be surprised how much wind can knock your setup out of alignment.  You wouldn't want to climb that tower in the middle of winter, would you?

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Musatcha is pronounced moo-SA-cha.  I have no idea where it originated.
Copyright 1998-2005, Brad Isbell []