William Sommerwerck wrote:

I knew an old ATT guy who worked in both cross country coaxial
& microwave video feeds. He told me how much of a pain it was to
equalize a section of cross county coax used for network TV feeds,
and keep it that way as the temperature changed.

Thanks for the confirmation. I didn't realize coax was so
temperature-sensitive.


You should see what it does to solid aluminum jacketed coax during a
sudden temperature drop. The shield can shrink three inches in a 500
foot run, and either pull the jacket out of the connector, or rip the
aluminum. It is called a suckout in CATV slang.

CATV mostly solved the problems by using the video carrier of two
channels to calculate the tilt, and compensate at each amplifier. The
systems I worked on used Ch. 2 & Ch. 12. That meant that any headend
needed a minimum of those two channels to work. A replacement signal at
the same level had to be provided at the head end if those were off the
air channels. We used locally generated video for both channels.

The ATT coax was miles long segments with tube amplifiers & equalizers
at fixed distances. Without careful setup of a hundred or more of those
terminals, the equalization destroyed the signal.


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