"Cecil Moore" wrote in message
. ..
Jerry Martes wrote:
"Cecil Moore" wrote in message
Yet in our above example
the stub is physically 90 degrees long and the source sees
+j500 ohms. The above stub is electrically 130 degrees long.

I'd disagree with a conclusion that, just because the impedance seen by
the source is 500 ohms, the line connecting it to a load is 90 degrees
long.

Well, it is physically 90 degrees long because the two
physical pieces are physically 45 degrees each. That's a
given. However, the +j500 result tells us that it is
electrically 130 degrees removed from the open circuit
at the far end.

There is a 45 degree delay through the Z01 section of stub.
There is a 45 degree delay through the Z02 section of stub.
There is a 40 degree phase shift at the Z01 to Z02 junction

If I disagree, do I have to get involved with some lengthy mathmatical
discussion? I'm not skilled enough to argue with you Cecil. I'm not
even smart. But, I sure dont see how anyone can conclude there is a
phase shift at the junction of two transmission lines.

There is an abrupt change in the Gamma angle of the reflection
coefficient at the impedance discontinuity. I can show you why
on a phasor graphic. Simplified, it goes something like this.

Itotal = 21.5*sin(25) = 10*sin(65)

where 21.5 is the phasor amplitude of the current in the 50
ohm section at the junction and 10 is the phasor amplitude
of the current in the 600 ohm section at the junction.

The values must be the same even though the magnitude of Z0,
which controls the amplitude of the current, has changed.
If those values must be equal and the amplitude changes because
the Z0 changed, the only other thing that can change is the
phase angle.
--
73, Cecil http://www.qsl.net/w5dxp

Hi Cecil

Thanks for pointing me toward learning about reflection coefficient. I
am really surprised that there is such a large amount of phase shift at that
junction.

Jerry