"Reg Edwards" wrote in message
Zo of ALL real, ordinary, transmission lines changes versus frequency
over
a
very wide frequency range.

Zo ranges over lots of thousands of ohms at a few cyles of seconds,
thousands of ohms at power frequencies, hundreds of ohms at audio
frequencies, and from tens to a few hundred ohms from 100KHz up to as
many
GHz as you like.
---
Reg.



Are we talking the same thing for Zo ? That a piece of say rg-8 (
whatever
they want to call it now) that is 50 ohm coax is not 50 ohms over its
normal
operating frequency range ?

=============================

What is your normal operating frequency range?

Here is Zo typical of cable similar to RG-58 versus frequency.

Nominal Zo = 50 ohms.
Degrees = Angle of Zo.

Freq Zo Degrees
------ ------- -------
10 Hz 3000 -45.0
100 Hz 950 -44.9
1000 Hz 301 -44.1
10 KHz 97 -36.4
100 KHz 54.2 -10.1
1 MHz 50.0 -2.6
10 MHz 48.4 -0.84
100 MHz 48.0 -0.26
1 GHz 47.8 -0.08

Superimposed on the above Zo vs F characteristics are manufacturing
reel-to-reel variations of 2 or 3 percent.
----
Reg, G4FGQ


Think I must have missed the point about REAL transmission lines. Trying to
keep up with too many discussions at one time. I was thinking of the simple
formular where frequency is not mentioned. I do know about the problem of
making the coax exectally the same all the time where even in the same reel
of coax you can get into suckout problems due to slight variations in the
coax.