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nelson mandela bay's family lifestyle
author:
xandre van der berg
so this is how a radio works
issue:
7, spring 2008
Nelson Mandela Bay and the invention of radio is synonymous. Join people talk magazine as we explore this technology that was created more than 100 years ago and is still one of the most popular components of modern media. In 1896 a guy with the name of Guglielmo Marconi was granted the world's first patent for wireless telegraphy – the radio! Marconi experimented for two years and eventually made radio contact with Edward Jennings right here in Port Elizabeth. In 1899 Jennings erected the first local radio transmitter on the Donkin Reserve and achieved a record transmission distance of 12½ kilometers. A request was made to the Cape Parliament for research funding, but this request was rejected, the reason being “life is troublesome enough with ordinary telegrams. With wireless telegraphy it will be unbearable.” It seems resistance to change is about the only thing that never changes. . Persistence paid off, though. An agreement was reached to establish a signal station on Dassen Island with the intention of communicating with Robben Island or the mainland. In 1923 the first South African radio broadcast, for entertainment purposes, was of a music concert held in Johannesburg on 18 December. Five years later rugby fans sat glued to their sets, listening to the first rugby test match on radio, played by the Springboks. Perhaps life in 1928 and 2008 is not so different? But how does it work? A radio is sometimes called a receiver, because they receive signals from a distant radio station. The station is called the transmitter –it sends out the signal. These signals are called radio waves and are spread out from the station in the same way as ripples or waves spread out across water after a pebble is dropped in a pool. Today, most transmitters from which radio waves are sent, are some distance away from the studios where programs are prepared. The sound of a radio broadcast starts its journey at the microphone. In essence the microphone “translates” sounds into an electric current that could be “translated” back into sound. Radio waves travel at the same speed as light waves – about 300 000km per second. If we were able to see them, they would look pretty much like ocean waves. The only difference, these radio waves are made of electric current. There is no danger of “shocking” yourself – unless you're tuned to bad radio, but that is a different kind of shock. The current of these waves is much weaker than the electricity going through the wires in your house, simply because radio-waves travel very long distances and spread outward as they go. Like a microphone, the wires of a transmitter already have an electric current going through them – consistently sending out radio-waves. Adding the “sound carrying electric current” to these waves, changes the shape of the waves being sent and produces the voice or music that will be received. This is called modulation. Let me explain. Remember the pebble in the pool? When the pebble meets the water, waves spread out in circles. These waves are like the unmodulated signal of a radio transmitter. If you drop a second pebble, in the exact same spot of the first, before the waves of the first pebble die away, a second set of waves will be generated and these waves will mingle with the first set of waves, making the water more choppy. The second set of waves is the “modulation”. Modulated radio-waves have quite a distance to travel. Just like the puddle's waves, the transmitted signal becomes weaker over distance and as they reach your radio, they must be “made stronger” again, in order for you to hear the sound. The signal must be “amplified”, they say, by your radio's “amplifier.” Then your radio must “translate” the waves or current back into sound – this is done through the loudspeaker. In the loudspeaker the electric current travels on a coil of wire around a magnet. Around this coil there is a diaphragm – sort of a cone – usually made of thick paper. It is this cone that does the translation work, back into sound. The “sound-waves” that come out of the loudspeaker are the same shape as the “sound-waves' that went into the microphone and so you can hear something that is happening very far away. Luckily, just like the waves in the ocean, radio waves have different lengths. This is good, because if radio waves were all the same length, then we would only be able to have a single radio station. When you “tune” your radio you set it to choose a specific “wave-length” on which your favorite radio station transmits. The “call-sign” of a radio station refers to the “wave-length” the station uses for transmitting the electric current that carries its sound. And do not imagine for one moment “radio” is just about music or your favorite breakfast show. Radio has changed our existence creating appliances such as mobile phones, baby monitors and even wireless technology for your computer. And it is not only about sound anymore – even pictures and data is “translated” into electric current and sent on invisible waves. To think our city was part of this great discovery!
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