What is FM ?

This results in better signal quality than AM because environmental factors do not affect the frequency the way they affect amplitude, and the receiver ignores variations in amplitude as long as the signal remains above a minimum threshold.

This results in better signal quality than AM because environmental factors do not affect the frequency the way they affect amplitude, and the receiver ignores variations in amplitude as long as the signal remains above a minimum threshold.

Shortwave radio

Shortwave radio

Shortwave radio uses frequencies in the HF band, from about 1.7 MHz to 30 MHz, according to the National Association of Shortwave Broadcasters (NASB).

Within that range, the shortwave spectrum is divided into several segments, some of which are dedicated to regular broadcasting stations, such as the Voice of America, the British Broadcasting Corporation and the Voice of Russia.

Within that range, the shortwave spectrum is divided into several segments, some of which are dedicated to regular broadcasting stations, such as the Voice of America, the British Broadcasting Corporation and the Voice of Russia.

Throughout the world, there are hundreds of shortwave stations, according to the NASB. About 25 privately owned shortwave stations are licensed in the United States by the Federal Communications Commission.

Shortwave stations can be heard for thousands of miles because the signals bounce off the ionosphere and rebound back hundreds or thousands of miles from their point of origin, according to the NASB.

Shortwave stations can be heard for thousands of miles because the signals bounce off the ionosphere and rebound back hundreds or thousands of miles from their point of origin, according to the NASB.

FM stereo

As two-channel stereo music gained popularity, so did the demand for stereo radio broadcasting.

However, one-channel (monaural, or mono) radios were already in wide use and were likely to remain so for the foreseeable future. The problem, then, was to create a system that could produce stereo music but still be compatible with existing mono receivers.

However, one-channel (monaural, or mono) radios were already in wide use and were likely to remain so for the foreseeable future. The problem, then, was to create a system that could produce stereo music but still be compatible with existing mono receivers.

Higher frequencies

Higher frequencies

Higher frequencies

Outer space is teeming with radio sources. These include planets, stars, gas and dust clouds, galaxies, pulsars, and even black holes. These sources allow astronomers to learn about the motion and chemical composition of these sources as well as the processes that cause these emissions.

According to Robert Patterson, a professor of astronomy at Missouri State University, astronomers use large radio telescopes to map cold neutral hydrogen clouds in galaxies.

These clouds are of particular interest because they line up along the spiral arms of galaxies such as the Milky Way, allowing scientists to map the clouds' structure.

Specific radio frequencies corresponding to the resonant frequencies of common atoms and molecules have been reserved by the FCC for exclusive use by radio astronomers to prevent radio transmitters from interfering with observations by extremely sensitive radio telescopes. A list of these frequencies is available from the National Astronomy and Ionosphere Center website.

Specific radio frequencies corresponding to the resonant frequencies of common atoms and molecules have been reserved by the FCC for exclusive use by radio astronomers to prevent radio transmitters from interfering with observations by extremely sensitive radio telescopes. A list of these frequencies is available from the National Astronomy and Ionosphere Center website.

According to NASA, radio astronomers often combine several smaller telescopes, or receiving dishes, into an array in order to make a clearer, or higher-resolution, radio image. For example, the Very Large Array (VLA) radio telescope in New Mexico consists of 27 antennas arranged in a huge "Y" pattern up to 22 miles (36 km) across.

According to NASA, radio astronomers often combine several smaller telescopes, or receiving dishes, into an array in order to make a clearer, or higher-resolution, radio image. For example, the Very Large Array (VLA) radio telescope in New Mexico consists of 27 antennas arranged in a huge "Y" pattern up to 22 miles (36 km) across.

Radio telescopes can also detect quasars, which is short for quasi-stellar radio source.