"Reg Edwards" wrote in message ...

Dear Dr Slick, it's very easy.

Take a real, long telephone line with Zo = 300 - j250 ohms at 1000 Hz.

Load it with a real resistor of 10 ohms in series with a real inductance of
40 millihenrys.

The inductance has a reactance of 250 ohms at 1000 Hz.

If you agree with the following formula,

Magnitude of Reflection Coefficient of the load, ZL, relative to line
impedance

= ( ZL - Zo ) / ( ZL + Zo ) = 1.865 which exceeds unity,

and has an angle of -59.9 degrees.

The resulting standing waves may also be calculated.

Are you happy now ?
---
Reg, G4FGQ


Nope. Re-do your calculations, and you will get something like
0.935:

Actually, my first posting was right all along, if Zo is always
real.

From Les Besser's Applied RF Techniques:

"For passive circuits, 0=[rho]=1,

And strictly speaking: Reflection Coefficient =
(Zl-Zo*)/(Zl-Zo)

Where * indicates
conjugate.

But most of the literature assumes that Zo is real, therefore
Zo*=Zo."


And then i looked at the trusty ARRL handbook, 1993, page 16-2,
and lo and behold, the reflection coefficient equation doesn't have a
term for line reactance, so both this book and Pozar have indeed
assumed that the Zo will be purely real.

That doesn't mean Zl cannot have reactance (be complex).

Try your calculation again, and you will see that you can never
have a [rho] (magnitude of R.C.)greater than 1 for a passive network.

How could you get more power reflected than what you put in? If
you guys can tell us, we could fix our power problems in CA!

But thanks for checking my work, and this is a subtle detail that
is good to know.


Slick