OTHER TECH

Indoor or outdoor?TV broadcasts rely on line-of-sight transmission, which means you have to be able to draw a straight line through the air from the antenna to the source of the signal. (Usually, the signal comes from the transmission tower, but sometimes a strong reflection off a hill or building will do the trick.) If the tower is below the horizon or blocked by hills or large buildings, you won't be able to receive anything. As a general rule, the higher the antenna, the better the reception. So most of the time, you'll be way better off installing a rooftop or attic antenna than having something on top of your TV. But if you live in a city or a nearby suburb, a good indoor antenna designed mainly for UHF reception might work fine.

How big does the antenna need to be? The farther you live from the stations, the more "gain" your antenna will need in orer to deliver a strong enough signal to an HDTV tuner. Antenna gain tends to be related to size - bigger is better. But UHF signals have higher frequencies than VHF, which means shorter wavelengths, so you don't need as big an antenna for UHF.

A great resource for figuring out what antenna type, directionality, and gain are best for your area is antennaweb.org. I've found that its color-coded suggestions are sometimes optimistic, so when you buy, consider going a step up in gain and directionality. The site also shows where the broadcast towers are located relative to your house.

Will an antenna amplifier make a difference? Mounting a low-noise amplifier, or booster, at the antenna is often useful even in the suburbs, and it might be essential if you live in a fringe area. If your situation doesn't allow for an antenna big enough to provide adequate gain on its own, you'll definitely need an amp. That's why indoor HDTV antennas usually have them built in. Antenna amplifiers from companies like Channel Master and Winegard typically cost between $50 and $80.

What about cabling? VHF antennas usually have 75-ohm outputs designed for shielded coaxial cable, while UHF antennas sometimes have 300-ohm outputs for unshielded twin-lead cable. But since HDTV tuners usually have only 75-ohm coaxial inputs, you should use a simple balun transformer (available at RadioShack) to convert any 300-ohm connection to 75-ohm at the antenna.

For short runs, like from an indoor antenna near the TV, just about any old piece of coax will do. But signal loss and interference can become a problem with longer runs - that's why you'll want to use high-quality cable with a foil shield as well as a braided one. You'll typically have less signal loss with RG-6 (especially at high UHF frequencies) than with the thinner RG-59, but performance can vary within these categories. So a really good RG-59 might do a better job than a mediocre RG-6. Fortunately, you can find product specs for high-frequency loss on the Web sites of major cable manufacturers like Belden (belden.com) and Canare (www.canare.com). The less attenuation per foot or meter at a given frequency, the better.

Should I install the antenna myself? If you're handy (and brave), there's no reason you can't install a rooftop antenna yourself. But outdoor antennas have to be properly grounded, and pulling coax through walls can be a challenge if you don't have the right tools or training. In other words, most of us are better off letting a professional do it.

A knowledgeable installer can also help with antenna selection. The key word here is "knowledgeable." (After the guys who put up my antenna left, I discovered that they had aimed it in the wrong direction!) He should know at least as much about selecting an HDTV antenna as you do. If not - if he recommends a VHF antenna, for example - find somebody else.