NEC-LIST: coaxial cable

I want to say a few words about coaxial cable. I was born in November
of 1909 and have watched the development of a few electrical
components. The first coax I used was in the year 1938 (maybe '39) .
Lead covered electrrical wire was pressed into service in an
experimental current sampling system for an early AM radio station
directional antenna. The work was directed by Jack DeWitt, then chief
engineer of Nashville station WSM. The story we heard in those days
was that the value of 51.5 ohms surge impedance originated from the
early experiments with water pipe forming coaxial conductors. As best
I remember, 1/2 inch copper water pipe was placed within a larger
copper pipe of 1 1/2 inch diameter and the surge impedance was
measured at 51.5 ohms, and this became the standard. As you know,
water pipe size figures do not agree with actual measured sizes of the
pipe.
Received on Thu Mar 15 2001 - 05:06:34 EST