Roy Lewallen wrote:
Ah, the drift and misattribution has begun. I'll butt in just long
enough to steer it back.

I made no premises, and have not made any statement about energy in
reflected waves. I only reported currents and powers which I believe are
correct. Nothing you or anyone has said has indicated otherwise. I do
question the notion of bouncing waves of average power, ...

That's exactly the false premise I am talking about, Roy. If you assume
waves of reflected power don't exist, you will find a way to rationalize
proof of that premise. You are looking under the streetlight where
the light is better instead of in the dark spot where you lost your
keys (keys being analogous to reflected power).

It's not a 200 ohm line, it's a 50 ohm line. (I see that I neglected to
state this when giving my example, and I apologize. But it can be
inferred from the load resistance and SWR I stated.)

Yes, you are right about that. But one can visualize the interference
by inserting 1WL of lossless 200 ohm feedline between the source and
the 50 ohm line which changes virtually nothing outside of the 200
ohm line.

100v/50ohm source with 80v at the output terminals.

80v--1WL lossless 200 ohm line--+--1/2WL 50 ohm line--200 ohm load

The source sees the same impedance as before. The same impedance as
before is seen looking back toward the source. Voltages, currents,
and powers remain the same. But now the interference patterns are
external to the source and can be easily analyzed.

It baffles me how you think you can calculate the line's stored energy
without knowing its time delay.

The time delay was given at one second, Roy. I really wish you would
read my postings. Here is the quote from the earlier posting:

************************************************** *****************
* If we make Roy's lossless 50 ohm feedline one second long (an *
* integer number of wavelengths), during steady-state, the source *
* will have supplied 68 joules of energy that has not reached the *
* load. That will continue throughout steady state. The 68 joules *
* of energy will be dissipated by the system during the power-off *
* transient state. *
************************************************** *****************

I DIDN'T EVER TRY TO CALCULATE THE STORED ENERGY IN YOUR LINE. But a
VF could be assumed for your lossless line and a delay calculated
from the length. Or you can just scale my one second line down to a
one microsecond line. The results will conceptually be the same. Of
course, the one microsecond line would have to be defined as an integer
number of half wavelengths but the frequency could be chosen for that
result.

So 68 microjoules would be be stored in that one microsecond feedline,
50 microjoules in the forward wave and 18 microjoules in the reflected
wave. The source is still supplying 32 microjoules per microsecond and
there is exactly enough energy stored in the feedline to support the
energy in the forward wave and reflected wave as predicted by the wave
reflection model or S-parameter analysis.

The calculation of stored energy is
simple enough, but it requires knowledge of the line's time delay.

The time delay was given, Roy, at one second. See the above quote.
That technique changes watts to joules. Buckets of joules are not
as easy to hide as watts.

A
half wavelength line at 3.5 MHz will store twice as much energy as a
half wavelength line at 7 MHz, all else being equal. Even if you knew
the frequency (which I didn't specify), you'd also need to know the
velocity factor to determine the time delay and therefore the stored
energy. I'm afraid your methods of calculating stored energy are in error.

I'm afraid you don't read my postings. THE FREQUENCY AND VELOCITY FACTOR
DO NOT MATTER WHEN THE FEEDLINE IS SPECIFIED TO BE ONE SECOND LONG.
Wavelength and VF are automatically taken into account by the assumption
of a one second long feedline. I have used that example before for
that very reason. A one second long feedline is filled with joules.
Joules are harder to sweep under the rug than watts are.

But if you think the stored energy is important and you find (by
whatever calculation method you're using) that it's precisely the right
value to support your interesting theory, modify the example by doubling
the line length to one wavelength. The forward and reverse powers stay
the same, power dissipation in source and load resistors stay the same,
impedances stay the same -- there's no change at all to my analysis or
any of the values I gave. But the energy stored in the line doubles.
(Egad, I hope your stored energy calculation method isn't so bizarre
that it allows doubling the line length without doubling the stored
energy. But I guess I wouldn't be surprised.)

If the forward power and reflected power remain the same, doubling the
length of the feedline must necessarily double the amount of energy
stored in the forward and reflected waves. That fact supports my side
of the argument, not yours.

So if the stored energy
was precisely the right amount before, now it's too much by a factor of
two. And if you find you like that amount of stored energy, double the
line length again.

Feeble attempt at obfuscation. The amount of energy stored in a feedline
is proportional to its length assuming the same forward and reflected
power levels and assuming integer multiples of a wavelength. Again,
that supports my side of the argument 100% - and doesn't support yours.
It appears to me that you have just admitted your mistake but don't
realize it yet.

I can see why you avoid the professional publications.

Actually, I have had a lot more articles published in professional
publications than I will ever have published in amateur publications.
I was an applications engineer for Intel for 13 years and professional
publication was required in the job description.
--
73, Cecil http://www.qsl.net/w5dxp

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