Cecil Moore wrote:

Jim Kelley wrote:
As far as I know, V/I ratios don't "cause" anything.

They sometimes cause 'rho' which then becomes an end
result and not the cause of anything.

I disagree. Reflections are caused by real impedances not reflected
ones.
Have you changed your mind about this?

At a two-port
network with reflections, rho usually cannot be calculated
from the physical impedances involved.

It can certainly be done using the optical formulas for a pair of
boundaries.

For the two boundaries as a network, and we call rho at the first
boundary r12 and rho at the second boundary r23 then
rho(network) = (r12 + r23)/(1 + r12*r23) = 0. Note that if we use your
value for r12, the network generates a reflection. I note the utility
of negative rho in this example.

But, with a transmission line at odd multiples of lambda/4, rho for the
network would be at a maximum and the network equation would be
(r12 - r23)/(1 - r12*r23). In such a case you'd want to use a load
impedance that would provide a r23 of +.5. (x - 150)/(x + 150) = .5,
so x = 450.

The moral is be
careful about saying that rho causes anything. Rho may
be only the end result of everything.

No question that rho is the end result of a ratio of impedances. It's
been my view that, like the V/I ratios we were speaking about, rho is
not a cause but a result.

73, Jim AC6XG