"Cecil Moore" wrote in message
...
Tam/WB2TT wrote:
I am not quite sure what you are saying. But, I ran a SPICE simulation
of
the following:
1V 1MHz source with resistor R0 feeding a 50 Ohm 250 ns transmission
line
shorted at the far end. Independent of R0, in steady state the voltage
at
the input end of the transmission line will be 1V. The effect of R0 is
to
limit how long it takes to reach steady state. For R0 = 50 Ohms, it is
one
cycle; for R0 = 500 Ohms, it is about 8 cycles, as eyeballed off the
waveform display.

Does SPICE report the steady-state forward and reflected waves
or just the superposition of those two waves? We all know what
they look like when superposed. The question is whether the
identity of the forward and reflected waves disappear after
they are superposed. To the best of my knowledge, the very
existence of standing waves requires the existence of a forward-
traveling wave and a rearward-traveling wave.

I have asked for examples of standing waves void of rearward-
traveling waves and none has been forthcoming.
--
73, Cecil http://www.qsl.net/w5dxp
It shows the composite voltage waveform, and the net current. Exactly what a
Bird wattmeter would do. Of course the Bird only shows you steady state,
Spice (SWCAD) swhows how you got there.

Tam/WB2TT

Tam/WB2TT wrote:
It shows the composite voltage waveform, and the net current. Exactly what a
Bird wattmeter would do.

That's not what a Bird wattmeter does. A Bird wattmeter possesses
a directional coupler. SPICE apparently does not. Is it possible
to add a directional coupler to SPICE? If you know the Z0, the net
voltage/current magnitudes/phases, it should be possible to use
phasor addition/subtraction to obtain the forward and reflected
components, just like the Bird wattmeter does.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:
the
rearward-traveling momentum energy in those two waves is conserved by
changing direction to become part of a forward-traveling wave.

Yeeesh. You had it on, dog, up until that. And don't try to tell me
(again) that I'm lying that you said it.

(Remember when you wrote this? "If reflected energy makes its way back
into the final amp, it was never generated in the first place, by
definition." Hint: apply the same idea to your "rearward-traveling
momentum" and you'll have it.)

73, Jim AC6XG

Jim Kelley wrote:

Cecil Moore wrote:
rearward-traveling momentum energy in those two waves is conserved by
changing direction to become part of a forward-traveling wave.

Yeeesh. You had it on, dog, up until that. And don't try to tell me
(again) that I'm lying that you said it.

(Remember when you wrote this? "If reflected energy makes its way back
into the final amp, it was never generated in the first place, by
definition." Hint: apply the same idea to your "rearward-traveling
momentum" and you'll have it.)

Egads Jim, exactly how much of reality do you think I am capable of
ignoring? Obviously, not as much as you. Why not just say, "God is
the cause of everything I (Jim) cannot explain or understand."?
The meaning would be virtually identical to your present positions.

I *don't* agree with that definition above and your implication that
momentum and energy don't need to be conserved is simply metaphysics
in action. You can argue against energy conservation all you want.
*Conservation of Momentum* has got you over a barrel in this argument
whether you realize it or not. Somehow, the momentum in the wave
reflected from a mismatched load is reversed. Please explain how
that happens without changing directions. Somehow, the energy in
the wave reflected from a mismatched load changes directions. Please
enlighten us on exactly the mechanism involved. Hint: J.C.Slater
explained it all in _Microwave_Transmissions_ before you were born.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:

Jim Kelley wrote:

Cecil Moore wrote:
rearward-traveling momentum energy in those two waves is conserved by
changing direction to become part of a forward-traveling wave.

Yeeesh. You had it on, dog, up until that. And don't try to tell me
(again) that I'm lying that you said it.

(Remember when you wrote this? "If reflected energy makes its way back
into the final amp, it was never generated in the first place, by
definition." Hint: apply the same idea to your "rearward-traveling
momentum" and you'll have it.)

Egads Jim, exactly how much of reality do you think I am capable of
ignoring?

You're evidently capable of ignoring at least some, Cecil.

I *don't* agree with that definition above and your implication that
momentum and energy don't need to be conserved is simply metaphysics
in action.

We both know that momentum and energy must be conserved. We just
disagree agree on how nature chooses to do that. And, because of that
disagreement, I'm forced to endure your beligerant rhetoric.

73, Jim AC6XG

Jim Kelley wrote:
We both know that momentum and energy must be conserved. We just
disagree agree on how nature chooses to do that.

Well then, please enlighten us, Jim. How does nature choose to
reverse the momentum in the wave reflected from a mismatched
source? It is obvious that the wave reflected from a mismatched
source has momentum in the rearward direction. Exactly what
reverses that momentum? Please be specific. Remember that standing
waves prove that the rearward-traveling wave exists in reality and
thus possesses energy and momentum in the rearward direction, both
of which must be conserved.

Maybe you should read _Microwave_Transmission_ by J. C. Slater
before you continue?
--
73, Cecil http://www.qsl.net/w5dxp



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Henry wrote,

I know that any power not dissipated by an antenna is reflected back to the
transmitter. Then the transmitter "reflects" this reflection back to
antenna, ad nauseum until its all gone. I also know that a short or an open
is required to reflect power and I'm searching for which it is, an open or a
short. I'm inclined to think it's a virtual open but I'm at a loss to
understand that and I wonder if someone has a good explanation or analogy
and some math wouldn't hurt.
tnx
Hank WD5JFR



This post is guaranteed to get Cecil revivified. Here's a hint: quit thinking
solely in
terms of power, that's for fellows who want to explain how it all works without
going into
any of the complicated details. Get an undergraduate physics text that
discusses
waves, and read it, or, better yet, take a class. Take all explanations you
read in
amateur publications with a grain of salt. After you've done this, you still
won't be
able to argue with Cecil, because that requires an extensive knowledge of the
moronic,
unfair, and downright pathalogical debating techniques of which Cecil is a
master.
But, it will be harder for you to fall for some of the crackpot ideas you're
liable to
read on this newsgroup, and it will give you something to think about when
sipping
your after-dinner port.

73,
Tom Donaly, KA6RUH

Tdonaly wrote:
This post is guaranteed to get Cecil revivified. Here's a hint: quit thinking
solely in terms of power, that's for fellows who want to explain how it all
works without going into any of the complicated details.

Like Hewlett Packard in their AN 95-1 publication? "Another advantage
of the s-parameters springs from the simple relationship between the
variables a1, a2, b1, and b2, and *various power waves*. ... The previous
four equations show that s-parameters are simply related to power gain and
mismatch loss, quantities which are often of more interest than the
corresponding voltage functions."
--
73, Cecil http://www.qsl.net/w5dxp



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I just want to know the reflection physics in the Tx, no antenna tuner, just
a mismatched antenna. I recall no pysics book that tell me how the
reflection sees the transmitter.
73
Hank WD5JFR
There are no stupid questions, just stupid people asking!
"Tdonaly" wrote in message
...
Henry wrote,

I know that any power not dissipated by an antenna is reflected back to
the
transmitter. Then the transmitter "reflects" this reflection back to
antenna, ad nauseum until its all gone. I also know that a short or an
open
is required to reflect power and I'm searching for which it is, an open
or a
short. I'm inclined to think it's a virtual open but I'm at a loss to
understand that and I wonder if someone has a good explanation or analogy
and some math wouldn't hurt.
tnx
Hank WD5JFR



This post is guaranteed to get Cecil revivified. Here's a hint: quit
thinking
solely in
terms of power, that's for fellows who want to explain how it all works
without
going into
any of the complicated details. Get an undergraduate physics text that
discusses
waves, and read it, or, better yet, take a class. Take all explanations
you
read in
amateur publications with a grain of salt. After you've done this, you
still
won't be
able to argue with Cecil, because that requires an extensive knowledge of
the
moronic,
unfair, and downright pathalogical debating techniques of which Cecil is a
master.
But, it will be harder for you to fall for some of the crackpot ideas
you're
liable to
read on this newsgroup, and it will give you something to think about when
sipping
your after-dinner port.

73,
Tom Donaly, KA6RUH

Henry Kolesnik wrote:
I just want to know the reflection physics in the Tx, no antenna tuner, just
a mismatched antenna. I recall no pysics book that tell me how the
reflection sees the transmitter.

The reflected waves obey the laws of physics. The kicker is that we
don't know (and apparently cannot directly measure) the source impedance.
What the reflections can do is modify the designed-for load line through
superposition of the forward and reflected waves. Modification of the
designed-for load line is not desirable and, if unprotected, can cause
over-voltage, over-current, or phase problems.
--
73, Cecil http://www.qsl.net/w5dxp



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