Nope. It's a motorized rotating antenna. It's usually mounted on an antenna mast with tripod in the back of my pickup truck, or in various mutations that vary with size of the antenna and frequency. I used it for ham radio transmitter hunts and such, but haven't done much with it for many years. If you have a perfect signal source, no reflections, and no VSWR, rotating the antenna will display the exact antenna pattern on the oscilloscope screen. It's almost like radar. It works best when moving as the real signal shows up as a steady lobe on the pattern, while the reflections come and go at random. I intentionally did not describe my 2.4Ghz version because it's not finished, what I have doesn't work quite right, and I have illusions of selling it as a product. That will bring a new dimension to war driving.
Ballet experience is helpful. Actually, it's a common technique also used in ham radio transmitter hunts. Some of the local experts are amazing. Some wrap their radios in aluminium foil, exposing only a small part of the antenna, to reduce the sensitivity when close. Lots of other tricks. The problem with doing it using an 802.11b/g system is that the signal strength meter is often slothish and insufficiently granular. There is software that will give a much better RSSI reading, with good response time. Netstumbler will also do it if you increase the polling rate. The Lucent client manager also works well.
Well, it should work, but I've never tried it with a USB dongle. In a hallway, you will have many reflections which will probably obscure the direct signal. It works outdoors, but I've never tried it indoors. I don't think it will work.
Yes, in the coffee cup. It's described at the bottom of the page. SMA connector with 4mm of brass rod. A simple 1/4 wave feed. The coax is apparently not attached.
It's apparently not a construction article. I could grind out the numbers for the horn if you'd like. I just wanted to illustrate what a properly designed horn antenna looks like and how big a 16dBi gain horn would really look like. Basically, the horn aperature width controls the gain. The transition angle controls the bandwidth (smoother transitions or tapered horns have a wider bandwidth). The stub tuning screws tune for minimum VSWR. For ham radio satellite work, the bandwidth required is very small. Therefore, a rather abrupt transition angle will work just fine. For 802.11 bandwidths, the horn will be much longer.
Yep. Note that the W1GHZ waveguide feed articles are primarily intended to illuminate a dish antenna.
This can get messy fast. Basically, the gain of both the horn and the coffee can is mostly (not totally) dependent upon the aperature diameter. Equal size "mouths" of these antennas should have roughly equal amounts of gain. However, the horn has a much neater coax transition while the coffee can of equal diameter would spray RF all over the place from wall reflections.
Incidentally, selection of materials is important. The only reason the coffee can works is that the surface is tin coated. Skin effect causes all the RF to stay on the surface of the coffee can. Tin is non-magnetic so it's a tolerable RF conductor. However, a stove pipe is a different story. It's usually painted, not plated. The RF conducting surface is yucky magnetic steel, which is not so good a conductor. I'm amazed that it works at all. One of my friends was making 150Mhz cavity resonators out of stove pipe and found the skin effect losses to be substantial.
Gain is the sum of many factors and is difficult to generalize for a type of antenna. In this case, the coffee can waveguide feeds were designed to illuminate a dish antenna. The gain of the entire system is calculated (err... computed) in detail as a system, not just the feed. The gain provided by the dish part is usually much more than that of the feed horn. Therefore, small errors in the feed can be ignored as the overall gain is set almost entirely by the dish diameter. In other words, the gain of the coffee can is not an important consideration. It has a big effect on overall dish efficiency (overspray, under-illumination, vswr), but that is part of the dish gain, not the feed.