RadioBanter - View Single Post - Length of Coax Affecting Incident Power to Meter?

August 12th 03, 11:34 PM

(Dr. Slick) wrote in message . com...
....
You're right about this, and it reminds us that if there is any
loss at all, we theoritically move away from a purely resistive
characteristic impedance into a complex one. This furthers the
complexity on the problem, as we must expect reactance in our coax.

It's not just theory, it's practice and measurable. But it's not a
requirement that loss introduce reactance to Zo; it's just that if the
line is lossless it must have a non-reactive Zo. Clearly if L/C =
R/G, the impedance will be non-reactive.

Also, consider what reactance you do get in practical lines, at what
frequencies. What effect does frequency have on the reactance? Why?
Under what conditions will it really be a problem? Might the reactive
part be so small that it will be totally swamped out by variations in
the real part? Think a bit about how much it will or won't mess up
the measurements you want to make.

Cheers,
Tom