Cecil Moore wrote:
Reg Edwards wrote:

Many years back a similar sort of calculation was done for coax. Coax
does not suffer from proximity effect. It's easier to work out. The
answer was 75 ohms. That's how 75 ohms became the standard
comunications Ro.


I vaguely remember something about efficiency Vs power
handling capability being the difference in the 75 ohm
standard and the 50 ohm standard. Is that right?
--
73, Cecil http://www.qsl.net/w5dxp

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Page 5-15 of The ARRL UHF/Microwave Experimenter's Manual says:

"Consider that both power handling capability and cable losses vary with Zo.
It has been shown that cable losses are minimum at a characteristic
impedance on the order of 75 [Ohms], while power handling capability is
maximum at a Zo of about 30 [Ohms]."

(The book used the Greek symbol rather than [Ohms])

The quoted passage is in a chapter by Dr. Paul Shuch, N6TX, Professor of
Electronics, Pennsylvania College of Technology. At the end of the quote, is
an indication to see footnote 13 which is:

"Moreno, Theodore, Microwave Transmission Design Data, Dover Publications,
1948."

73,
John