Richard Clark wrote:

On Fri, 13 Apr 2007 16:37:02 GMT, Walter Maxwell
wrote:

The voltage reflection coefficient at the input of these two transmission lines is 1.0 at 180°, and the
current reflection coefficient at this point is 1.0 at 0°. These are the reflection coefficients that would be
found when measuring at any short circuit, no matter whether it is physical or virtual. Consequently, both
physical and virtual short or open circuits placed on a transmission line can cause reflections.


And here we get to the nut of the matter - causality. It is already
established that either the physical short, or physical open, whose
absence would render any correlation invalid, dominates the action.
The proof follows the quality of the physical open or the physical
short. A poor physical open or poor physical short will never be
improved by ANY transmission line mechanics. On the other hand, poor
transmission line mechanics will never deliver the action of the best
physical short or the best physical open.

I agree that this is the problem in Walt's otherwise brilliant work.
Reflections are only caused by the direct interaction between
electromagnetic waves and matter. It is nevertheless valid to say
that systems behave as though virtual impedances cause reflections.
Virtual reflection coefficients are a clever tool and methodology for
systems analysis. But it must be remembered that the propagation of
electromagnetic waves is effected only by certain physical properties
of matter, as described eloquently by James C. Maxwell and others.
Those fundamentals of wave behavior are not different in the steady
state than at other times.

A VIRTUAL short or open is metaphor, and it is an useful
metaphor for describing systems. What I see beyond these examples you
have provided are statements (in other discussions) that tend to
confer a reality to the VIRTUAL which is obviously a contradiction on
the face of it. Other than that, there is absolutely nothing in your
published work that is in dispute.

I completely agree. I think if we got past this one issue, the
newsgroup might actually find itself devoted more to discussions of
antennas.

73, Jim AC6XG