wrote:

Cecil Moore wrote:
Should have said |rho|. |rho| is often used without its Gamma angle.

It still remains incomplete. The sign is needed to know Vr.

The point was that Pref=0 and therefore, there is no sign to deal
with for rho=Sqrt(Pref/Pfwd). +0 = -0

And, of course, the sign information was lost as soon as Vf and Vr
were converted to power.

In the example case, Pref=0 and therefore rho=0. What difference does
the sign make when rho=0?

Thinking of black boxes is an excellent tool to assist in the search
for knowledge. As a tool, it can help identify which information is
critical to a solution and which is not.

That's true, but refusing to open the black box when it is possible to
do so to gain knowledge is sheer nonsense for truth-seekers. OTOH, it
is a great tool for someone who is seeking to obscure the truth and
promote the steady-state religion at all costs.

As a person searching for knowledge through thought experiments you
decide when to open the black box.

Yes, and what is the person, who then objects to the opening,
searching for?

Do consider adding this thinking tool to your toolbox. It is quite
powerful.

It is in my toolbox but it does not dictate my attitudes toward
reality. If it is finally possible to open the black box in
order to ascertain the truth, I will certainly open it. Before
that, I will subject it to TDR experiments, something you would
no doubt object to since it is not "steady-state". With a TDR,
it is duck soup to prove that an open-circuit 1/4WL stub is
not shorted at the mouth of the stub.

And yet you feel quite free to state that sometimes there is NO
reflection when there IS an impedance discontinuity. All I want
is some consistency.

I said there is no NET reflection at a Z0-match. I provided the
following s-parameter equation to illustrate that the two
reflections at a Z0-match will superpose and cancel each other.
b1 = s11*a1 + s12*a2 Do you understand the s-parameter equations?
If not, HP's AN 95-1 is available for download from the web.

If you wish to claim that there are no NET reflections at some
impedance discontinuities, then, for consistency, we should also
be able to claim that there are NET reflections when there is
no impedance discontinuity.

Goose and gander.

I suggest you study and understand the difference between a logically
inclusive statement and a logically exclusive statement. The difference
lies in the use of the word "some" Vs "all". Above you performed a
logical switcharoo when you went from "some" to an implication of "all".
That is known in logic as an "argumentum ad absurdum".

Sometimes, there are NET reflections at a physical impedance
discontinuity. If a single RF source signal exists, there are
always component reflections at a physical impedance discontinuity.

Sometimes, there are no NET reflections at a physical impedance
discontinuity because the two component reflections cancel. This
is true of Z0-matched systems with reflections.

Sometimes, there are net reflections existing where there is no
impedance discontinuity. They are the result of reflections at
a physical impedance discontinuity somewhere else. Reflected waves
are traveling waves. They travel from their point of origin to other
places in the system.

Sometimes, there are no net reflections where there is no impedance
discontinuity, e.g. a flat system.
--
73, Cecil http://www.qsl.net/w5dxp



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