Dwi Susilo

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Wireless Communications : Sea and Air Transceivers

The first wireless communications devices were radio telegraphs. A telegraph is a device that sends simple electrical pulses along copper wires or through the air as radio waves. The pulses were caused by contact between two metal surfaces, and receivers interpreted these electrical pulses as tones or beeps. A code of long and short signals was developed to represent the letters of the alphabet, and in this way coded messages could be sent between telegraphs. Radio telegraphs used radio waves rather than wire telegraph lines to send and receive messages. Radio telegraphs sent telegraph signals over long distances and were ideal for ship-to-shore communication. Bulky radio telegraphs were installed on ships as early as 1899 and were widely used by 1905. Maritime and aviation telecommunications systems now use high-frequency radios and satellites capable of transmitting speech and text, rather than wireless telegraphy, to send messages. Aircraft pilots use radios to communicate with air traffic controllers at airports and also to communicate with other pilots. Navigation beacons are equipped with transmitters that send automated signals to help ships and aircraft in distress determine their positions. While high-frequency radio can transmit signals over long distances, the quality of these signals can be diminished by bad weather or by electrical interference in the atmosphere, which is often caused by radiation from the Sun.