Radios are a very important part of our communication. For example it can be found in many places like…
in peoples hands (walkmans)
But when most people think of radios they might think of their favorite songs or music in general. But music isn't the only thing as you might already know but they have broadcasts with discussions, debates, advertisements and news.
Radios send us all this things by something called broadcasting. Broadcasting works by changing sound that comes from a studio into electromagnetic waves or radio waves. These radio waves travel to a control board. A technician is a person that works at the control board and they can change the sound by …
making it louder
making it softer
blending sounds together
After the radio waves go to the control board they go to a transmitter. A transmitter is a tower like device that strengthens the waves coming from the broadcast. this creates other radio waves called carrier waves. When the carrier waves are combined with the waves from the broadcast they form the radio signal that is sent. The transmitter can be located in the same room as the control board but the antenna could also locate it. The transmitter sends waves out into the air. You would most likely find an antenna in high, open areas away from buildings because it could possibly interfere with the radio waves.
Radio waves can travel at 186,000 mi. [299,792 km] per second. When the radio waves reach a radio receiver. The receiver changes the radio waves back into the original sound.
The longest waves in the electromagnetic spectrum (group of waves) are radio waves, and the shortest radio waves are called microwaves (not the kind in a kitchen). Microwaves are 0.04in. to 12 in. [1mm to 30cm] in length.
Microwaves are chosen over radio waves because…
they have better quality
send radio and television signals
they can send signals between Earth, spacecraft, and between satellites
The radio waves that are longer than microwaves are divided into 2 frequencies - VHF (very-high frequency) and UHF (ultra-high frequency). VHF waves are about 3.281 to 32.81ft [to 10m] length. UHF waves are about 0.3281 to 3.281fr (0.1 to 1m) in length.
The radio waves that are used in radio broadcasts, can be both microwaves and longer radio waves. These are transmitted in one of two ways: through amplification modulation or frequency modulation; also, known as AM or FM. In AM transmission, the strength of the carrier waves will vary as they adjust to match the waves coming out of the radio studio. However, the carrier waves are constant in FM transmission. The strength of the carrier waves are called amplitudes.
The antenna then sends out 2 different types of AM waves. The waves spread out horizontally and vertically. The horizontal waves are called ground waves, and the vertical waves are called sky waves. When the sky waves reach the ionosphere, they are then reflected back to earth. This allows the AM waves to be received over a wide range on area from the antenna. FM waves travel in the same way as the AM waves. But instead of being reflected back to earth, the sky waves pass through the atmosphere, into space. The AM ground waves can be received at larger distances than the FM horizontal waves. The main advantage of FM waves is that they are not affected by as much static as the AM waves. Electricity in the atmosphere causes static. Each radio station has an assigned channel (frequency). Which prevents stations from interfering with another stations broadcasts.
The first radio signals were sent in 1895, by an Italian inventor, Guglielmo Marconi. The signals traveled for more than 1 mile. Within a few years he was sending signals across the Atlantic Ocean, from England to New Foundland. In 1906, a Canadian physicist named Reginald A. Fessenden, was able to broadcast human speech. Then, Lee De Forest, an American inventor, produced radio show in 1910. In 1918, Edwin H. Armstrong developed the superheterodyne circuit. The first commercial radio station began broadcasting on August 20, 1920. That station, WWJ in Detroit also was able to broadcast the presidential election on November 2, 1920.
The digital radio is the newest in radio technology. It can produce truer sound that FM and it is not affected by static. Digital receivers are expensive, but digital radios are expected to replace the AM/FM radio, once it becomes less expensive. Today, there are over 9,700 privately owned radio stations in America. Each year sponsors spend billions on dollars on advertising. About 99 percent of American households own a radio. In America, the radio stations must follow the rules setup by the Federal Communications Commission (FCC).