In message , Michael A.
Terrell writes

Ian Jackson wrote:

In message , Michael A.
Terrell writes

Ian Jackson wrote:

In message , William Sommerwerck
writes
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.

Its attenuation changes by appx .02dB per dB per degree C.


At what distance? At what frequency?

Any and any.
Think about it.


I have. Let's say I have a 5000 foot piece of coax and a 5 foot
piece. One is used to 450 MHZ, and the other at 11 GHz. The change is
not the same.

You need a change per distance, and frequency, because each type of
cable has different loss characteristics.


OK.

At 450MHz and temperature T1 centigrade, your 5000 foot of coax will
have an attenuation of A1 dB.

[The value of A1 obviously depends on the characteristics of that
particular type of coax, and on its length. For a different frequency /
temperature / length / type of coax, the value of A1 will be different.]

At temperature T2, the change of attenuation will be approximately
(T2-T1) x 0.02 x A1 dB.


At 11GHz and temperature T1, your 5 foot of coax will have an
attenuation of A2 dB.

[Again, for a different frequency / temperature / length / type of coax,
different value of A1.]

At temperature T2, the change of attenuation will be approximately
(T2-T1) x 0.02 x A2 dB.

Essentially, you don't have to know anything about the frequency /
length / type of coax. Although these do determine the amount of initial
attenuation, all you need to know is the actual value of the initial
attenuation, and the change of temperature. The higher the initial
attenuation (for whatever reason), the greater will be the change of
attenuation.
--
Ian