Keith Dysart wrote:
On Dec 11, 10:34 pm, Roger wrote:
When the load is less than the Zo of the line, the currents
add but voltages subtract. Right?

I don't think so.
Vt = Vf + Vr, It = If - Ir, Vf = If * Z0 and Vr = Ir * Z0 are the
fundamental equations defining forward and reverse waves.

I think Roger is talking about the phase shift at a reflection
point. If ZL Z0, the current reverses phase, i.e.
It = |If| - |Ir| = 0. If ZL Z0, the voltage reverses phase,
i.e. Vt = |Vf| - |Vf| = 0

The sign on the reflected current is just a directional
convention left over from DC and is unnecessary as the phase
angle of the phasor values takes care of the signs.
Interestingly, the field of optics has a different convention.
--
73, Cecil http://www.w5dxp.com