Hüseyin FIRAT WHY RADIO STATIONS MUST STAY ON FM Radio waves are broadcast in a number of bands which contain each a range of frequencies and have different ways of travelling from point to point through the Earth's atmosphere. FM and AM broadcast frequencies operate in different ways and have very different characteristics. Generally, FM broadcast is used on radio stations. There are three reasons for the radio stations must stay on FM. These are: high sound quality, low transmitter power and low susceptibility to slight changes in amplitude. The first cause of prefered FM is high sound and music quality [3][5]. FM allows for a stereo signal, which is also essential to quality music broadcasting [4]. Also, bandwidth on FM is too many, so music quality is too clear and net [2]. It has a greater dynamic range, and it can handle sounds of higher and lower frequencies [4]. This is why music, with its much greater frequency range than the human voice, sounds better on FM radio [4]. The other cause of prefered FM is its transmitter power is low [2][4][5]. FM broadcasting is a low-power, low cost technology [4]. This is because FM waves can travel far even when transmitted by a low-power transmitter [2][4]. FM signal transmission can be done with low-power transmitter –often 250- watt transmitter [4]. The last cause of prefered FM is its low susceptibility to slight changes in amplitude. Most forms of electrical noise are naturally AM, and a FM receiver will not respond to AM signals [1][3]. FM receivers also exhibit a characteristic known as the capture effect. If two or more FM signals are on the same frequency, the FM receiver will respond to the strongest of the signals and ignore the rest [3]. You should note that FM waves can only travel as ground waves, and, therefore, the distance you can receive an FM signal from is limit by your (our, more specifically, your radio's) ability to "see" the radio transmitter tower. Once the tower is below your horizon, you lose the station. In our country, FM modulation is used on ground systems, AM modulation is used on air systems [6].
REFERENCES [1] Basic Electricity And Electronics, Delton T. HORN
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