A digital terrestrial receiver is a general term that includes digital radio receivers and receiving radio signals from land-based transmitters. Radio signals are electromagnetic (EM) waves that carry information and make wireless communications possible. A digital terrestrial receiver is tuned in to one frequency, the number of cycles per second of the radio carrier, at one time. When many transmitters are sending EM waves, the digital terrestrial receiver is able to distinguish by tuning in on the right frequency, which is called selectivity of the receiver.
Digital terrestrial receivers are able to reproduce information from a very weak signal. This is called sensitivity, which is measured usually in microvolts, or millionths of a volt. For instance, a digital terrestrial receiver can be confirmed as capable of receiving 0.25 microvolts under specific signal quality criteria. Improving the receiver antenna system can enhance the quality of reception. A better quality antenna or remounting the antenna on a higher location will usually improve signal reception quality.
Besides having good sensitivity and selectivity, the digital terrestrial receiver, which is sometimes referred to as a digital tuner, needs to have good audio reproduction quality. This is usually measured as levels of noise or distortion. A good quality of sound reproduction will have low noise and low distortion.
Digital terrestrial receivers are capable of various modulation types, which is how the carrier wave is modified to “carry” the information, such as news and music. Amplitude modulation (AM) changes the average intensity of the carrier wave in proportion to the information. Before digital terrestrial receivers were used, analog receivers had a high level of AM reception. One problem with AM, however, is that digital terrestrial receivers also receive most electrical noise.
Frequency modulation (FM) is also another way to pack a carrier with information. By changing the instantaneous frequency of the carrier in proportion to the information, FM has successfully made high fidelity and low-noise reproduction possible in both analog and digital terrestrial receivers. FM has been widely used in broadcast high fidelity and audio for analog television (TV). Before digital technology was available, FM stereo transmission and reception were already possible. There are tons of features available with digital technology and tools, including programmable channels and recording to various digital music formats, such as Moving Picture Experts Group-3 (MPEG-3) and Windows Media Audio (WMA).