Cecil, W5DXP wrote:
"How many joules are contained in that feedline?"

I`ll speculate that after one second, 200 joules are contained in the
forward wave on that line. Then, after two seconds, another 100 joules
has been reflected back toward the line feedpoint where it opposes
growth of power input to the line. Total joules on the line is 300.

Forward power minus the reflected power equals 100 watts being supplied
by the generator to the load with 200 watts forward power and 100 watts
reflrcted power in the line.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Cecil, W5DXP wrote:
"How many joules are contained in that feedline?"

Total joules on the line is 300.

That can be shown to be true by noting that during the
transient buildup to steady-state, 300 joules sourced
by the generator have not yet reached the load. That
remains true until the generator is powered down, i.e.
all during steady-state.

Forward power minus the reflected power equals 100 watts being supplied
by the generator to the load with 200 watts forward power and 100 watts
reflrcted power in the line.

But what about the people who say there's no energy in the
reflected wave? Reckon how they sweep all those joules,
whose energy must be conserved, under the rug? :-)
--
73, Cecil http://www.qsl.net/w5dxp

One should also carefully consider the
more interesting variation of the
problem: an open transmission line. In
the steady state we have 100 watts
forward, 100 watts reflected, 200 Joules
in the line, and 0 watts being sourced
by the generator. :-)

ac6xg

Cecil Moore wrote:
Richard Harrison wrote:

Cecil, W5DXP wrote:
"How many joules are contained in that feedline?"

Total joules on the line is 300.


That can be shown to be true by noting that during the
transient buildup to steady-state, 300 joules sourced
by the generator have not yet reached the load. That
remains true until the generator is powered down, i.e.
all during steady-state.

Forward power minus the reflected power equals 100 watts being supplied
by the generator to the load with 200 watts forward power and 100 watts
reflrcted power in the line.


But what about the people who say there's no energy in the
reflected wave? Reckon how they sweep all those joules,
whose energy must be conserved, under the rug? :-)

Jim Kelley wrote:
One should also carefully consider the more interesting variation of the
problem: an open transmission line. In the steady state we have 100
watts forward, 100 watts reflected, 200 Joules in the line, and 0 watts
being sourced by the generator. :-)

Yes, but the 200 joules in the line was previously sourced
by the generator during the transient state. It's hard to
sweep 200 joules under the reflected power rug.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Jim Kelley wrote:

One should also carefully consider the more interesting variation of
the problem: an open transmission line. In the steady state we have
100 watts forward, 100 watts reflected, 200 Joules in the line, and 0
watts being sourced by the generator. :-)


Yes, but the 200 joules in the line was previously sourced
by the generator during the transient state. It's hard to
sweep 200 joules under the reflected power rug.

So is this your proof that Joules of
energy are likewise reflected from
antireflective surfaces?

ac6xg

"Jim Kelley" wrote in message
...

Cecil Moore wrote:
Yes, but the 200 joules in the line was previously sourced
by the generator during the transient state. It's hard to
sweep 200 joules under the reflected power rug.

So is this your proof that Joules of energy are likewise reflected from
antireflective surfaces?

No, the two subjects are conceptually only distantly related so your
posting is a diverting of the above issue - changing the subject back
to an earlier thread:

Every impedance discontinuity causes reflections. An antireflective
surface is an impedance discontinuity, i.e. a change in the index of
refraction between two mediums. If properly designed, the anti-reflective
surface causes 100% destructive interference between the internal and
external reflections each of which contain joules of energy. It is easy to
prove
that the internal reflection contains joules of energy. If the external
reflection
didn't contain any energy, then destructive interference would not be
possible. Therefore, both reflections associated with an antireflective
surface must contain an equal magnitude of joules.

In his QEX article, Dr. Best gave us the physics equation that governs
100% destructive interference: Ptotal = P1 + P2 - SQRT(P1*P2).
Assuming that power cannot exist without energy, if the energy in P1
equals the energy in P2 and the associated waves are 180 degrees out
of phase, then of course 100% destructive interference occurs at the
antireflective surface. That's how antireflective surfaces and Z0-matches
work.
--
73, Cecil http://www.qsl.net/w5dxp

Jim Kelley wrote:
One should also carefully consider the more interesting variation of the
problem: an open transmission line. In the steady state we have 100
watts forward, 100 watts reflected, 200 Joules in the line, and 0 watts
being sourced by the generator. :-)

Expanding on my earlier response - For the first two seconds,
the source doesn't know it is looking into an open transmission
line so a 100 watt source would faithfully output 200 joules
into a one second long open circuit transmission line. That
200 joules cannot be destroyed. Is it mere coincidence that
the forward and reflected waves are 100 joules/sec*(one second),
exactly equal to the 200 joules supplied by the source?
--
73, Cecil http://www.qsl.net/w5dxp

is that line 1 second long, or 1/2 second long?? a 1 second long line would
take 2 seconds worth of energy from the generator before the reflection
returned to let it know the line is terminated. this is of course very
important if you are measuring lines with tdr's where you can really see
those returned waves, of course the time it takes them to get back to the
tdr is double the one-way travel time... mess it up and you are looking for
faults twice as far down the line as you calculate.


"Cecil Moore" wrote in message
. com...
Jim Kelley wrote:
One should also carefully consider the more interesting variation of the
problem: an open transmission line. In the steady state we have 100
watts forward, 100 watts reflected, 200 Joules in the line, and 0 watts
being sourced by the generator. :-)

Expanding on my earlier response - For the first two seconds,
the source doesn't know it is looking into an open transmission
line so a 100 watt source would faithfully output 200 joules
into a one second long open circuit transmission line. That
200 joules cannot be destroyed. Is it mere coincidence that
the forward and reflected waves are 100 joules/sec*(one second),
exactly equal to the 200 joules supplied by the source?
--
73, Cecil http://www.qsl.net/w5dxp

Dave wrote:
is that line 1 second long, or 1/2 second long?? a 1 second long line would
take 2 seconds worth of energy from the generator before the reflection
returned to let it know the line is terminated. this is of course very
important if you are measuring lines with tdr's where you can really see
those returned waves, of course the time it takes them to get back to the
tdr is double the one-way travel time... mess it up and you are looking for
faults twice as far down the line as you calculate.

The line is 1 second long. The source is generating 100 watts. So the
number of joules generated starting at t=0 is 100N where N is the
total number of seconds. At the end of 30 seconds, the generator will
have sourced 3000 joules which must be conserved.

I will generate an EXCEL spreadsheet at work today and post it to
my web page when I get home. It will cover the first 30 seconds
in 1 second increments. It will show that of the 3000 joules sourced
by the generator during that first 30 seconds, only 2700 joules have
reached the load. The other 300 joules are contained in the 200W
forward wave and 100W reflected wave.

(200 watts)(one second) = 200 joules in the forward wave

(100 watts)(one second) = 100 joules in the reflected wave

200 joules + 100 joules = 300 joules not delivered to the load
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

Jim Kelley wrote:

One should also carefully consider the more interesting variation of
the problem: an open transmission line. In the steady state we have
100 watts forward, 100 watts reflected, 200 Joules in the line, and 0
watts being sourced by the generator. :-)


Expanding on my earlier response - For the first two seconds,
the source doesn't know it is looking into an open transmission
line so a 100 watt source would faithfully output 200 joules
into a one second long open circuit transmission line. That
200 joules cannot be destroyed. Is it mere coincidence that
the forward and reflected waves are 100 joules/sec*(one second),
exactly equal to the 200 joules supplied by the source?

But you're missing, or trying to
circumvent, the most interesting aspect
of the problem. It's the one which
highlights the very core of our
disagreement. The energy stored in the
line, remains stored in the line as long
as steady state is maintained without a
single Joule of additional energy moving
into or out of the line. To me, this
illustrates clearly how the fields at
the impedance interfaces of a matching
transformer can be maintained without
requiring multiple rereflections of
energy. I'm hoping some day you'll see
it too.

73, ac6xg