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Old June 26th 10, 01:22 AM posted to rec.radio.amateur.antenna
Keith Dysart[_2_] Keith Dysart[_2_] is offline
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First recorded activity by RadioBanter: May 2007
Posts: 492
Default what happens to reflected energy ?

On Jun 25, 7:30*am, K1TTT wrote:
On Jun 25, 7:46*am, lu6etj wrote:





On 24 jun, 17:54, K1TTT wrote:


On Jun 24, 3:25*pm, Cecil Moore wrote:


On Jun 24, 9:20*am, lu6etj wrote:


Oh, I'm so sorry Cecil, I should have written "However I can not
visualize a simple PHYSICAL mechanism/example to generate
such system in a TL". Anyway, your additional info it is very useful to
me. Thanks.


The physical mechanism is the Z01==Z02 impedance discontinuity with
its associated reflection coefficient, rho. We can see that reflection
on a TDR so it is indeed a PHYSICAL mechanism.
--
73, Cecil, w5dxp.com


don't forget the OTHER physical mechanism that is necessary,
superposition... the ability to add voltages, currents, and fields in
linear circuits and media.


I mentioned same comment in another post. We use superposition
principle in two different contexts. Superposition theorem in circuit
theory, and wave superposition. Wave (traveling) superposition deals
with f(t,x,y,z) and usually with puntual magnitudes, E, H, D, B, etc)
while circuit theory deals with a subset f(t) phenomena and with
integrated magnitudes (V, I). Sometimes that becomes a confused
issue


Miguel


NO, superposition is always the same. *it is the linear addition of
currents or fields in a linear media. *it works the same for circuits
as for em waves.

the big problem are the people who confuse the formulas for adding
powers with adding fields or currents/voltages and forget the phase
terms.

the other big problem is keith who seems to want to separate his waves
into separate time and space variables and leaves out the requirement
that wave functions must be dependent on both space AND time.
basically any solution to the wave equations derived from maxwell's
laws must be of the form f(t-x/v). *this leads him to the erroneous
conclusions he gets from trying to compare his batteries to wave
propagation. *this is the same problem people have with standing
waves, they have separate dependence on t and x, so they can't travel
and can't transport energy.- Hide quoted text -


I see that the stress induced by considering DC waves is causing you
to misinterpret my writings.

May I suggest an alternate exploration for you. Assuming that you
accept TDR and know how to use Reflection Coefficients to compute
voltage and current reflections, then consider what happens
when a rectangular pulse is launched from a matched generator in
to a transmission line. For simple reflection coefficients like
0, 1, and -1 compute the reflected pulse. For both the forward
and reflected direction compute the voltage and current on the line
before the pulse arrives, as it passes and after it has passed.

Compute the energy in the pulse, and how long a distance it
occupies on the transmission line. Compute the power as the
pulse is passing.

Be sure you know what happens to the pulse when it re-enters
the generator. For simplicity, assume a generator constructed
using the Thevenin circuit.

Make sure all the results are in agreement; especially, the
energy delived by the source and the energy dissipated in the
various resistors.

Now make the pulse longer and longer... until it looks like
a step function. And do the computations again.

Determine if the results agree with those I previously
presented for the DC example.

....Keith

PS: Barring errors, they will.