Radio Type
AM: AM radio is radio broadcasting using amplitude modulation. This was the dominant system of radio in the first two thirds of the 20th century, and it remains important into the 21st.Because of the inferior sound quality of AM broadcasting, the medium lends itself particularly to talk radio, while music radio has in recent decades tended to be broadcast using FM.AM radio technology is simpler than other types of radio, such as FM radio and DAB. An AM receiver detects the power of the radio wave and amplifies changes in the power measurement to drive a speaker or earphones. The earliest crystal radio receivers used this principle. FM: FM radio is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation to provide high-fidelity broadcast radio sound.DAB Digital Audio Broadcast or DAB is a standard for digital radio broadcast developed by EUREKA as a research project for the European Union. (Project number EU147.) The technology was mainly developed in the 1980s, although the project started in the year 1987 and ended in 2000. Over 285 million people around the world can receive more than 550 different DAB services. The United Kingdom was the first country to receive a wide range of radio stations via DAB, with over 50 commercial and BBC services available in London in 2001.The DAB Forum represents more than 30 countries. The United States is not among them and uses IBOC to deliver digital radio.DAB uses the Eureka 147 protocol based on orthogonal frequency division modulation for transmitting digital data over a lossy radio channel.DAB broadcasts use the MP2 audio coding technique, a close relative of the popular MP3 format, which was also created as part of the EU147 project.DAB has the advantage that stations do not have be re-tuned as you move from area to area, such as in a car. Also, you can receive "radiotext" (in DAB terminology, Dynamic Label Segment, or DLS) from the station giving information such as song titles or traffic updates.Problems with the name Digital occurred with radios, as "digital" can be associated with a digital method of tuning, which is commonly found on analogue radios with LCD displays, rather than a digital signal. RDS: Radio Data System, or RDS, is a standard for sending small amounts of digital information using conventional FM radio broadcasts. The RDS system standardizes several types of information transmitted, including time and station identification. RDS is widely used in Europe, but less so in North America.Radio Broadcast Data System is the official name used for the U.S. version of RDS, though the "RDS" name seems to be at least as common in usage. The two standards are nearly identical, with only slight differences, mainly in which numbers are assigned to each of 31 musical and other program formats the RBDS system can identify. RBDS was approved by the NRSC, RDS by the EBU.
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