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Old May 16th 05, 01:29 PM
Reg Edwards
 
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I should have mentioned, the Manchester-Leeds Number 1 Coaxial Cable
had an impedance of 75 ohms. The impedance at which, for a given
price of copper, in those far-off days, had the lowest attenuation per
mile. 75 ohms has stuck as the Standard..

The distance between Manchester (then the centre of the cotton
industry) and Leeds (then the centre of the woolen industry), by road,
over the beautiful Lancashire and Yorkshire moors, is about 40 English
miles. By correct choice of impedance the conscientious engineers of
that age could have saved as much as £5,000 per mile in the price of
copper, to be formed in the manufactories into copper tapes for outer
coaxial conductors, and drawing copper wire from 3-ton billet-form
down to exact precision-size wire through water-cooled diamond dies.
It was and still is a precision manufacturing industry.

More savings occur in the distance between repeater stations. If
attenuation performance requirements can be met with one fewer
repeater station, the cost of a whole building, power supplies and
transmission equipment can be saved.

Although communications have shifted to digital, cables still matter.
But eventually optical fibers will take over the long distance
communications.

Radio Amateurs, with a little money to burn, never become involved
with such mundane matters. They are more interested in what they
imagine the SWR meter tells them. But if that keeps them happy then
so be it. I am an amateur myself. I have a call sign which sounds
very nice in morse code. Why should I disillusion them?
----
Reg, G4FGQ





 
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