When I got satellite TV installed at my house a few years ago, I had a regular VHF/UHF antenna put in at the same time so that I could receive high-definition TV broadcasts. Over-the-air was the only game in town for HD back then. Now, with the major cable companies embracing high-def, and with satellite-TV services offering more and more high-def channels, HDTV is easier to come by. But satellite and cable can't reach everyone, and the only way a lot of people can get the high-def versions of the major networks is by using an old-fashioned TV antenna.

That's not necessarily bad, though. Once you've paid for the antenna, the programming's free. And as long as you can pull in a strong, clean signal, the picture and sound will be a stunning improvement over anything you've experienced on regular TV.

You'll have no trouble finding all kinds of antennas at big electronics retailers like RadioShack, Circuit City , and Best Buy. The key is to make sure you get the right one and set it up properly — which you can ensure by considering a few basic questions.

What kind of antenna do I need?
Most high-def channels are in the UHF band (Channels 14 through 83), and many of the rest are in the VHF high band (Channels 7 through 13). Even if, say, your local ABC station broadcasts regular TV on Channel 2 and lists its HDTV channel as 2-1, it might actually be transmitting it on something like Channel 44. (A good resource for finding out about local high-def channel assignments is antennaweb.org.)

Chances are good that a UHF antenna (about $50 to $85) will work fine if you only want to receive high-def. But if you want VHF, whether for HDTV or regular TV, or you want to use the antenna to pick up FM radio as well (the entire FM band is nestled between TV Channels 6 and 7), get a VHF/UHF/FM antenna (about $35 to $85).

An omnidirectional antenna, which is equally sensitive to signals from all directions, can work well if you live in a flat area that's relatively near the transmission towers for your local stations. But usually, you'll be much better off with a directional antenna aimed at the towers. And if you live near an airport, like I do, a directional antenna can help prevent signal reflections off low-flying planes from disrupting your reception (or at least minimize the problem).

To figure out an antenna's directionality, you need to know the spec for its front-to-back ratio, or the difference between its sensitivity in front and 180° behind. The higher the number in decibels (dB), the greater the directionality, or the more tightly it's focused in one direction. If you can receive HDTV broadcasts from more than one direction but can't go with an omnidirectional antenna, you'll have to get a directional antenna and use a remote-controlled motorized rotor to aim it.

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.

ANTENNA TYPES


Zenith’s ZHDTV1Z Silver Sensor is a directional indoor UHF antenna meant to be aimed directly at the HDTV signal.



Able to pick up an HDTV signal’s reflection off nearby buildings and other large obstructions as well as directly, Winegard’s very directional SquareShooter UHF/VHF antenna is designed for urban and suburban areas where multipath is a problem.



RadioShack’s VU-90XR attic/outdoor antenna can pick up UHF, VHF, and FM radio signals.