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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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