On Dec 8, 3:15 pm, "AI4QJ" wrote:
"Gene Fuller" wrote in message

...





Cecil Moore wrote:

---43.4 deg 600 ohm line---+---10 deg 100 ohm line---open

The Smith Chart does make it clear what is happening.
Here is the math to go with it. The impedance at the
junction of the two lines is:

-j100*tan(90-10) = -j100*tan(80) = -j567 ohms
-j600*tan(43.4) = -j600*tan(43.4) = -j567 ohms

The phase shift at the junction of the two lines is:
80-43.4 = 36.6 degrees

Time permitting, I will work up the phasor diagrams of
the component voltages (or currents) at the junction
where rho = (600-100)/(600+100) = 0.7143

So how many nanoseconds does that 36.6 degree phase shift represent?

8-)

In this example, we have transmission lines, not an antenna or antenna coil.
The total phase shift is 90 degrees or 62.5 nsec.

Only with great stretching.

The 10 degree 100 ohm line contributes 6.94nsec,

Correct.

the 43 degree 600 ohm line contributes 29.86 nsec.

Correct.

But now think in the time domain for a bit.
29.86 nsec after the signal is first applied it reaches the
discontinuity. 29.86 nsec later the first reflection arrives
back at the start. 13.8 nsec later the first reflection from
the end of the 100 ohm section arrives back at the start.
It takes many more reflections of reflections before the
impedance at the input starts to look like a short.

Nowhere in here will you be able to find anything that
happens in 62.5 nsec.

This is quite unlike an actual physical 1/4WL stub
where the first reflection does arrive back in
2 * 62.5 nsec. And the impedance at the input
behaves like a short after exactly 125 nsec.

Of course the ultimate is an actual short, where
Cecil's 90 degrees happens immediately.

These 90 degrees that Cecil insists are "always"
present are quite difficult to locate.

....Keith

Keith Dysart wrote:
These 90 degrees that Cecil insists are "always"
present are quite difficult to locate.

For anyone who knows how to use a Smith Chart,
those degrees are quite easy to locate.
--
73, Cecil http://www.w5dxp.com

Keith Dysart wrote:


It takes many more reflections of reflections before the
impedance at the input starts to look like a short.

An excellent point, Keith. And applications for it abound.

Problem is that it conflicts with the predictions made by the power
propagation model. (The politically correct name is the Joules/sec
propagation model.) That model shows that only a single reflection of
power is needed to explain the whole thing. Of course in some cases
the wave of power has to figure out how to turn around and go back the
other direction after it's been cancelled in order to conserve energy.
(A problem it wouldn't have to solve had it not violated it in the
first place.) Admittedly, some of the details have yet to be worked
out. :-)

73, ac6xg

Jim Kelley wrote:
Problem is that it conflicts with the predictions made by the power
propagation model. (The politically correct name is the Joules/sec
propagation model.) That model shows that only a single reflection of
power is needed to explain the whole thing. Of course in some cases the
wave of power has to figure out how to turn around and go back the other
direction after it's been cancelled in order to conserve energy. (A
problem it wouldn't have to solve had it not violated it in the first
place.) Admittedly, some of the details have yet to be worked out. :-)

Wow Jim, you need to repeat Fields and Waves 310. :-)
You have misunderstood virtually every principle
of the wave reflection model.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Jim Kelley wrote:

Problem is that it conflicts with the predictions made by the power
propagation model. (The politically correct name is the Joules/sec
propagation model.) That model shows that only a single reflection of
power is needed to explain the whole thing. Of course in some cases
the wave of power has to figure out how to turn around and go back the
other direction after it's been cancelled in order to conserve energy.
(A problem it wouldn't have to solve had it not violated it in the
first place.) Admittedly, some of the details have yet to be worked
out. :-)


Wow Jim, you need to repeat Fields and Waves 310. :-)
You have misunderstood virtually every principle
of the wave reflection model.

I wouldn't presume to take credit for any of the above. I learned it
on r.r.a.a. from someone who I think needs to take Fields and Waves 1.
:-)

73, ac6xg

Jim Kelley wrote:

Cecil Moore wrote:
Jim Kelley wrote:
Problem is that it conflicts with the predictions made by the power
propagation model. (The politically correct name is the Joules/sec
propagation model.) That model shows that only a single reflection
of power is needed to explain the whole thing. Of course in some
cases the wave of power has to figure out how to turn around and go
back the other direction after it's been cancelled in order to
conserve energy. (A problem it wouldn't have to solve had it not
violated it in the first place.) Admittedly, some of the details
have yet to be worked out. :-)

Wow Jim, you need to repeat Fields and Waves 310. :-)
You have misunderstood virtually every principle
of the wave reflection model.

I wouldn't presume to take credit for any of the above. I learned it on
r.r.a.a. from someone who I think needs to take Fields and Waves 1. :-)

If you are talking about me, you have either misunderstood
what I said or you enjoy bearing false witness. Here's a quote
from my 2005 magazine article at:

http://www.w5dxp.com/energy.htm

"The author has endeavored to satisfy the purists in this
series of articles. The term "power flow" has been avoided
in favor of "energy flow". Power is a measure of that energy
flow per unit time through a plane. Likewise, the EM fields
in the waves do the interfering. Powers, treated as scalars,
are incapable of interference. Any sign associated with a power
in this paper is the sign of the cosine of the phase angle
between two voltage phasors."

Also, here is an EXCEL spreadsheet version of what happens
during the transient buildup to steady-state.

http://www.w5dxp.com/1secsgat.gif

Do you really consider 30 iterations to be only a single
reflection?
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:

Jim Kelley wrote:


Cecil Moore wrote:

Jim Kelley wrote:

Problem is that it conflicts with the predictions made by the power
propagation model. (The politically correct name is the Joules/sec
propagation model.) That model shows that only a single reflection
of power is needed to explain the whole thing. Of course in some
cases the wave of power has to figure out how to turn around and go
back the other direction after it's been cancelled in order to
conserve energy. (A problem it wouldn't have to solve had it not
violated it in the first place.) Admittedly, some of the details
have yet to be worked out. :-)


Wow Jim, you need to repeat Fields and Waves 310. :-)
You have misunderstood virtually every principle
of the wave reflection model.


I wouldn't presume to take credit for any of the above. I learned it
on r.r.a.a. from someone who I think needs to take Fields and Waves
1. :-)


If you are talking about me, you have either misunderstood
what I said or you enjoy bearing false witness. Here's a quote
from my 2005 magazine article at:

http://www.w5dxp.com/energy.htm

Hi Cecil -

Yes, I'm very familiar with that article. You've already posted a
link to it dozens of times on this newsgroup. It very clearly
illustrates exactly those thing which I may have somewhat more
'colorfully' restated above, and more. It includes equations with
variables for forward and reflected power all throughout, a reference
to a supposed "4th mechanism of reflection" (that's the magical way in
which waves of power and energy change direction), and illustrations
with arrows named Pref showing how power is reflected at impedance
discontinuities.

Back when our corresponence was more cordial, I advised you not to
write those things. And now you'd like to deny having done it; all
the while portraying me as a liar. You're beautiful, man.

73, ac6xg