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Microwave magic

15th August 2014

By: Terry Mackenzie-hoy

  

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When I was younger, we used to escort my father on many occasions to the airport in Johannesburg, then known as Jan Smuts Airport. The road was a single lane and it took about an hour to get to the airport from where we lived.

These days, even with traffic, it is not more than 40 minutes. On the road to the airport, on the left, was the antenna farm for the main radio transmission station for the airport. At the time (1960 to 1970), all airport communication to distant aircraft was by means of shortwave radio and, to cover the very long distances involved, the ground radio transmitters had to be connected through a whole number of very powerful radio antennas, or aerials, all located in a park, known as a ‘farm’.

The Jan Smuts antennas were all of different types, many very beautifully constructed: there were dipoles, fan dipoles, Zepps, two-element quads, Yagi and folded Yagi, all made of well-ordered wires and insulators strung together to create vast wire sculptures. We passed it often on the way to and from the airport.

Then, the other day, I passed the antenna farm – to see no wire antenna structures. They had all gone. In their place were a whole lot of small transmitter antennas, of the type you see on houses and which connect the local security firm to a house alarm. I realised what had happened; in this satellite era, it is now no longer necessary to communicate by means of shortwave radios – all you need is to bounce the signal to a satellite and there you are, sorted.

I feel sad – it is the passing of some wonderful engineering. The electrical engineers’ equivalent of the sadness mechanical engineers must have felt with the passing of the steam engine. No more fan dipoles, no more Yagis. Truth to tell, this replacement of information transmission media had been upon us for some time – we just did not see it. All over the country, we used to see telephone poles with up to 24 wires, transmitting telephone conversations from one place to another. Now you will notice that some telephone poles that used to have 24 wires on insulators have no more than four; all the voice and data traffic is carried by microwave dishes and fibre-optic cables – if it is not going through cellphones.

I call this the ‘move away from copper-based communication’. One could become sentimental about it but there is one huge advantage – there is so much less copper out there to steal.

Recently, in Cape Town, a whole lot of security guards who used to patrol the main train lines to prevent copper theft were dismissed over a pay dispute. As a result, they cut many signal cables in the Cape Town main line, bringing the train operations to a halt. Many thousands of employees were late for work and, naturally, with no security guards, theft of copper cables will start again.

The obvious solution to this will be the abandonment of the copper-wire signalling system for a global position system microwave-linked dish system. It will be expensive to replace equipment that is not yet obsolete but theft will reduce since there will be less to steal.

Ironically, when this happens, the marginal and unemployed will be in a worse condition than before. With nothing to steal, incomes will reduce, and if there is no need to guard against theft, employment of security guards will reduce. It is the same for all the copper-based communication systems – increased reliability of microwave and satellite communication means fewer maintenance staff. If noncopper-based systems are simple to install, there will be a reduction in the requirement for trained installation technicians.

Oddly, this country will be among the leaders in adopting sophisticated communication systems. In many other countries, theft of copper, strikes and vandalism are not as rampant as here. South Africa has more pressing reasons to change – other countries can change when copper-based communication equipment become obsolete and those trained in installation and maintenance reach retirement age. In South Africa, change has to happen to keep things running – job losses are inevitable. Which is a pity.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

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