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And then consider the energy
flow just in front and just following the voltage step as it propagates down the line and back and down and back... ======================= Kelvin had trouble with voltage steps when trying to predict signalling speed on the first Atlantic telegraph cable. They went ahead, chartered the Great Eastern steamship, steamed West and laid the thing anyway. Shortly afterwards it broke. Kelvin was created a Lord for his un-finished services and had a bridge named after him. But it was indeed a difficult problem in that day and age. Twenty years later, hard-of-hearing Heaviside invented a brand new branch of mathematics, the Operational Calculus, to solve that particular, and a great number of other problems. For HIS services to mankind, as a revolutionary, he was derided by the pompous Establishment whose members resorted only to plagiarised text books. Heaviside only had a Layer named after him. To their own credit, it was American communications engineers who eventually acknowledged his genius. But then, Americans always did have sympathetic feelings towards revolutionaries. What amazes me is the amount of trouble some modern American engineers still appear to suffer from on the subject of propagation of an electric current along a pair of wires. Wires have been around a long time now. Instead of thinking in terms of frequency and waves why not do as Oliver did and try time and waveshape. It worked for him. Exactly what, where and when is being reflected becomes clear. And if anybody enjoys playing with numbers just replace 'j-omega' with 's' (It was 'p' when I first played with it.) Incidentally, the concept of wire-gauges originated in my home city, Birmingham, England. Faraday was familiar with it. It was internationally known as the BWG. The Americans, just to be different, changed theirs to AWG. Now (nearly) everybody has gone metric. ;o) ---- Reg, G4FGQ |