Tarmo Tammaru wrote:
there would be no other explanation for standing waves,

May I suggest that you consider charge.
Consider how static charge can store energy in the capacitance of the
line.
Consider how moving charge can store energy in the inductance of the
line.
Consider how the charge moves to change the energy distribution within
the line.
Do it for a pulse of charge; then for multiple pulses.
Consider what happens when the pulses collide; consider pulses of the
same polarity and different.
Do it for a step of charge; then make the step so long it looks like DC.
Do it for sinusoids.
Do it for opens, shorts and terminated lines.
Do it for matched, unmatched and disconnected sources (disconnect just
after injecting the pulse, step or sinusoid).
Do it for sources at both ends of the lines.

And soon you will have an explanation which does not require waves
travelling up and down the line to explain the observed voltages and
currents of the standing 'wave'.

....Keith

W5DXP wrote:
Ian White, G3SEK wrote:
Yes! That principle of impedance substitution is so simple, so
fundamental, some people never notice it's there at all.

And you would apparently like to pull the wool over the eyes of everyone
who notices that the definition of impedance has changed in the process.
Shame on you for that attempt at obfuscation!

You are using that principle of impedance substitution whenever you
calibrate your antenna impedance bridge using known values of resistORS,
capacitORS and inductORS.

Of course *you* are aware of the difference in what's connected to the
instrument - you have more information than it has. The only claim Bill
and I have been making is that you cannot tell the difference from any
*electrical* measurement made at a single frequency in the steady
state... and those were exactly the conditions that burned up your
transmitter, so the substitution principle is valid for this branch of
the discussion.

That whole principle relies on the fact that, at the same frequency and
in the steady state, the "definition of impedance" in terms of its
electrical properties does *not* change. That's the whole point.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

wrote:
And soon you will have an explanation which does not require waves
travelling up and down the line to explain the observed voltages and
currents of the standing 'wave'.

Yes, soon you will have some mathematical shortcuts. But do mathematical
shortcuts really cause photons to flow sideways between an equivalent
capacitance and an equivalent inductance? Can you describe a bench
experiment where photons are transferred from a capacitor to an inductor
and back?
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote:

W5DXP wrote:
In a nutshell, what laws of physics get repealed
just as steady-state is achieved?

Sorry, that's not worthy of a reply.

OK, I'll answer it. No laws of physics get repealed just as
steady-state is achieved. All the steady-state model does is to
allow some mathematical shortcuts. (But it does not allow photons
to oscillate locally between equivalent lumped circuit constants.)

Some people apparently believe that those steady-state mathematical
shortcuts turn around and effect reality. Causing something happen in
reality by just thinking about a mental model is the domain of religion,
not science. The steady-state model does NOT effect reality. Conditions
on a transmission line are exactly the same whether the steady-state
model is used or not. Nothing magic, like disappearing standing waves,
happens at the instant steady-state is achieved.

Too many engineers believe in the primacy of consciousness rather
than in the primacy of existence.
--
73, Cecil http://www.qsl.net/w5dxp



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Ian White, G3SEK wrote:
You are using that principle of impedance substitution whenever you
calibrate your antenna impedance bridge using known values of resistORS,
capacitORS and inductORS.

Yes, but I comprehend what I am doing. For you to imply the "electrical
properties don't change" between a 50 ohm dummy load and a 50 ohm dipole
antenna is simply ridiculous.

That whole principle relies on the fact that, at the same frequency and
in the steady state, the "definition of impedance" in terms of its
electrical properties does *not* change. That's the whole point.

The electrical properties *can* change and that's the whole point. The
electrical properties of a 50+j0 dummy load and a 50+j0 antenna are
almost completely different.

A transmission line can transfer photons. Can a lumped constant L-C
model transfer photons?
--
73, Cecil http://www.qsl.net/w5dxp



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Ian, G3SEK wrote:
"A related topic would be the effect of tank circuit Q on bandwidth of
HF amplifiers;"

Class A amplifiers are little used as HF finals, so in practical
amplifiers current is only part-time.

Impedance of a parallel resonant circuit is high. Circuit impedance
rises with inductance. Q rises with capacitance.

A Class C plate tank introduces a load on tube or transistor. It should
waste only a small percentage of the power generated. It should have
enough Q to linearize the output of the amplifier.

Terman says it is easy to show that the Class C tank circuit efficiency
is: 1 - Qloaded/Qunloaded.

Loaded Q is the ratio of the circulating volt-amperes to the transmitted
watts. If Q is too high, bandwidth is too narrow. If Q is too low,
harmonics are high.

As Q is ordinarily high, the tank circuit impedance is higher than the
load on the amplifier.

Impedance on the Class C amplifier has little effect on the tube or
transistor loading. Output impedance presented by the transmitter to the
load is determined in many cases by the percentage of the time the
amplifier is switched-off.

Best regards, Richard Harrison, KB5WZI

Cecil,

Try this out. For a line driven by a sin wave, there is a lumped parameter
equivalent circuit with impedance R + JX for any line length and any
termination. For a line exited by a pulse, this equivalent circuit is an
infinite series with nuls at n/PW; there is no length of line where the line
is resonant.

Tam/WB2TT
"W5DXP" wrote in message
...
Do steady-state signals obey one set of laws of physics and pulses
obey a different set of laws of physics?

W5DXP wrote:
Ian White, G3SEK wrote:
You are using that principle of impedance substitution whenever you
calibrate your antenna impedance bridge using known values of
resistORS, capacitORS and inductORS.

Yes, but I comprehend what I am doing. For you to imply the "electrical
properties don't change" between a 50 ohm dummy load and a 50 ohm dipole
antenna is simply ridiculous.

I didn't either say that or imply it. What's truly "ridiculous" is for
you to *infer* that I did.

I think I've already made my points well enough for other readers to
judge, so I really am done this time.

No doubt you'll have the last word, Cecil. Use it well.

--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Was Descartes an engineer??

DD, W1MCE

W5DXP wrote:

Roy Lewallen wrote:

[SNIP]

Too many engineers believe in the primacy of consciousness rather
than in the primacy of existence.

I left out the word "tank" in the sentence: Tank impedance on the Class
C amplifier has little effect on tube or transistor loading." Sorry.
Sometimes I delete too much when I shuffle things on the screen, I
should write it first.

Best regards, Richard Harrison, KB5WZI