Thursday, September 02, 2010

How To Share Your WiFi With Your Neighbor

First .... An often overlooked point is to check your Terms of Service. Your ISP may forbid sharing, and there may be HEAVY penalties. Some ISP's are friendly to it. Check on it!

To reiterate the basics of the technology:

1) Line Of Sight (LOS) is an essential ingredient.

If you have a window in location #1 where you can put the AP and sit your client in the window at location #2, and they have clear line of sight and distance is reasonable, it can be done. Let this much be clear, 2.4 GHz is the same frequency your microwave oven uses, and there is a reason it heats up food so well. Water molecules absorb 2.4 GHz radio very nicely, which is why it get hot when you bombard it in the oven. If you have a bunch of trees in the way, they are full of water, and there is very little chance you are going to get a signal through many trees over a long distance. Getting LOS is essential, and if you need to go higher to get it then do it.

2) An amplifier is no substitute for a good antenna and LOS!

If we are at a party and you want to chat with me from across the room, is it a good idea to whip out your bullhorn? No, it's quite stupid. Now I can hear you but you still cannot hear me. WiFi is 2-way, it is not AM-radio. The next answer will be "let's all get bullhorns" but then we all go deaf. There is a smarter way. A cone held to your ear will let you hear better.

A good high-gain antenna will let you hear weak signals as well as you transmit, so it is in every way superior. Usually cheaper too. The best solution is often a directional antenna which will enhance transmit and received in a particular direction, with the side-benefit of rejecting interference sources in other directions. Try even the simple home-made antennas from

3) To connect two networks wirelessly or to extend wireless, the ideal solution is to get a REPEATER. Normally this has TWO radios so that no significant loss of throughput occurs. One can essentially make a repeater by using the coupling of two devices, an ethernet adaptor bridge(to capture) and wire it to an AP (to retx).

Let me attempt to explain the "obstruction in the way" :

You have a candle sitting in a windowsill. With clear LOS (Line of Sight) you can see this candle from a long distance on a dark night. You might need binoculars further away.

Now you put a house or a thick stand of trees in the way. You cannot see the candle anymore! I would point out that "amps" are no help since they boost maybe to 1 Watt. How bright is a 1-Watt light bulb? Not very. The problem is not insufficent power, it's that house in the way!

To put it quite simple the nature of WiFi is low-power and not very penetrating. Metals and any material with water in them (i.e. TREES) cut your range drastically.

The correct solution is to get clear LOS. Most people do this by putting an antenna on a mast up high enough to see over the obstruction. At least from altitude with a good directional antenna you have a better shot at it.

Alternatively you could put up a repeater station on the top of the obstruction.

Now if you have any personal experience .... good or bad .... feel free to share by leaving a comment.

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