Jim Kelley wrote:
(150-50)/(150+50) is NOT rho.

Is it the reflection coefficient for a 50 ohm to 150 ohm impedance
discontinuity?

Relating this question to the s-parameters as explained in HP's
ap note AN 95-1, s11 is the input reflection coefficient when the
load reflection coefficient is zero. s'11 is the input reflection
coefficient with an arbitrary load reflection coefficient.

s'11 = s11 + [s12*s21(ZL-Z0)/(ZL+Z0)]/[1-s22(ZL-Z0)/(ZL+Z0)]

So s'11 is the rho to the left of '+' in the previous diagram.
That's the rho on the 50 ohm line.

s'11 = rho

s11 equals rho only when Z-Load = Z0, i.e. (ZL-Z0)/(ZL+Z0)=0
--
73, Cecil, W5DXP