A tuner selects which radio frequency is desired and is commonly incorporated with a receiver, which accepts the AM/FM radio signals. You can think of it as a radio without speakers or an amplifier; a separate source component.

Because most tuners are integrated into receivers, people often use the two words interchangeably. (This can get confusing, because amplifiers are sometimes called receivers, too. See " receivers/amplifiers.")

Why buy a receiver without a built-in tuner? Often a separate tuner will have more features than the tuner included with the receiver. Plus, the electronics of a receiver can, if poorly constructed, cause interference with the radio or other sources. A separate tuner avoids potential interference problems. In addition, more care goes into designing and building separate components. This quality can make the difference between crystal clear reception and static.

Digital Radio

Construction on the road to digital radio began in April, 1997, when the FCC auctioned broadcast spectrum licenses for satellite-delivered digital audio radio service (S-DARS) to two providers, CD Radio and XM Satellite Radio. The services promise to deliver CD-quality AM and FM radio reception nationwide but initially only to car radios.

The two competing S-DAR subscription services deliver 50 digital radio channels via silver-dollar-sized disc antennas that attach to the rear window of a car, and to an inexpensive radio card that plugs into a cassette or CD slot in a car's head unit.

Features

Different tuners use varying technologies in their receivers such as quartz, digital and phase-locked loop (PLL) tuning. There are subtle differences in tuning technologies, but all do a fine job of tuning in and locking in signals.

The most common way to choose a station is with manual tuning--the large knob you turn until you hear a station clearly. Most tuners have a digital display--turn the knob clockwise, the numbers in the display go up; turn it counter clockwise, the numbers go down.

As an alternative, many manufacturers offer electronic tuners, which scan the frequencies and stop only on those on which they can receive a signal. If you like the station, press another button, and the station is added to memory and can be recalled simply by pushing that button. This is called a station preset. Many tuners are differentiated by the number of AM and FM station presets that can be programmed.

Some manufacturers find this method time consuming and offer a keypad for you to input directly the frequency of the stations yourself. Some tuners include a remote control, which allows you to do this from your seat.

Smart Radio

The most common tuners are simple AM/FM models. But many tuners are equipped with Radio Broadcast Data System (RBDS or RDS). RDS is often called "smart radio" for its special features. For instance, you can search for radio stations by 25 different program types (such as top 40, country, college, jazz, talk, sports or news).

Radio stations can send special text messages to appear on the display (station call letters, song titles, artists and lyrics, phone numbers for ticket offers and request lines, and advertisements).

Instead of the eight-character display used in automobiles, home RDS radios can offer a 64-character display to transmit stock quotes, sports scores, weather reports and other information. Many smart radios can turn on automatically to alert you of a public emergency.

Additional features in RDS radios for cars are discussed on the mobile audio web pages.

AM Stereo

AM stereo is a step-up feature in some tuners. Standard AM signals are in mono, and sound emanating from both speakers is a mono signal split in half.

AM radio stations must install stereo equipment to render their signal stereo, and you need a component receiver designed to receive and translate AM stereo/AMAX signals.

When you tune in participating stations, you'll notice improved reception and reduced noise and distortion.

Antennas

FM broadcasts are susceptible to many forms of interference that can ruin reception. An antenna, no matter where it is located, locks in weaker radio signals and reduces background noise.

Unless you are located a long distance from broadcast stations, an indoor antenna may suit your needs. The old-style dipole antenna (one type is commonly known as rabbit ears) has given way to disc, wedge and obelisk-shaped antennas that improve reception and are not as conspicuous. Some indoor antennas are only six inches high. These new antennas can either be passive or powered antennas that are effective at pulling in and holding distant or weak stations.