Cecil Moore wrote:
Isn't the 50 ohms that causes rho=0 on the 50 ohm feedline
simply the V/I ratio at point '+'?

I see now. Your interested in something else here, I think. The rho
for the whole network which includes both impedance discontinuities is
indeed zero. We've talked about that before. But the rho for the
single discontinuity at '+' is not equal to zero. The reflected
impedance (the load impedance, repeated a half wavelength away) is not
considered in the evaluation of rho at '+'. It is the characteristic
impedance of the line that is considered. You would agree, no?

73, Jim AC6XG