Understanding Microwave Radio Signals

2007-06-06 Word Count: 520 Category: Communications

A micro wave radio system sends signals through the atmosphere between towers spaced about twenty to thirty miles apart, amplifies the signals and retransmits them at each repeater station until they reach their destination. Microwave radio operates at high frequency end of the radio spectrum. The signals follow a straight line path and the relaying antennas must be within sight of each other. One of the principles problems affecting microwave signals is the variation caused by the changes in the atmosphere. Moisture and temperature conditions can make the radio beam bend, resulting in fading.
The primary advantage of microwave radio's that it can carry thousands of voice channels without physically connected cables between points of communication, thus avoiding the need for continuous right of way between points. Further radio is better able to span water, mountains, heavily wooded terrain that poses barriers to cable installation. Most long distance links today are coaxial cable or microwave radio.
The tall towers with large horns or dish antennas that can be seen in the country are repeater system for radio link systems. These systems are popular for carrying large quantities of data and voice traffic because they do not require right of way acquisition between towers, they just require the purchase or lease of only a small area of ground for installation of each tower. Because of their very high operating frequencies they can carry large quantities of information per radio systems. Because the wavelength of the transmitted signals is short, an antenna of reasonable size focuses the transmitted signals into a beam. This capability provides much greater signal strength at the receiver without increasing transmitter power.
Radio link systems are subject to transmission impairments that limit the distance between repeater points and cause other problems. The microwave signals are attenuated by solid objects including the earth, and the higher frequencies are attenuated by rain, snow, fog and dust, reflected from flat conductive surfaces like water, metal surfaces, diffracted around solid objects, refracted by the atmosphere so the beam may travel beyond the distance and be picked up by an antenna that is not supposed to receive it.
In spite of these problems, radio link systems are highly successful and carry a substantial part of all telephones, data and television traffic. The microwave range of radio frequencies is allocated for various purposes by international treaty. Most common carrier radio link systems carry analog signals principally frequency modulated.
There are a few systems however that carries digital signals. Terrestrial radio link systems are point to point that is the signal is transmitted in a beam from a source microwave antenna across the earth's surface to the antenna at which it is aimed. The width of the beam varies between one degree to five degrees depending on the transmission frequency and antenna size. As a result the transmission is highly directional which is desirable if the information is intended for only one destination, such as for a telephone conversation. For many applications however the information has multiple destinations, as for television broadcasts, which makes satellite radio link system more practical and desirable.

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Tymon Hytem has worked in the electronics feild for the past 15 years. He enjoys helping people decide on electronic gadgets from telephones to XM Radio and choosing the perfect XM Satellite Radio system for their needs.