what happens to reflected energy ?
 

On Jul 6, 12:26*am, Keith Dysart wrote:
On Jul 5, 8:33*am, Cecil Moore wrote:



On Jul 4, 8:08*pm, Keith Dysart wrote:

The system I have in mind has ports through which energy can flow in
or out of the system and components inside the system which can
store energy. For such a system, the energy flowing in to ports
of the system minus the energy flowing out of ports *must
equal the increase in energy being stored in the system.

This must be true at all times, or energy is being created or
destroyed; a bit of a no-no.

But you are not tracking energy - you are tracking power. As Roy has
said, there is no requirement that instantaneous power must balance.
Where are the stored energy terms in any of your instantaneous power
equations? How do you handle the difference in dimensions between
energy and power? The only condition for which NET power must balance
is during a time interval in which there is zero NET stored power,
e.g. during one cycle.

I have rev'ed my zero interference article to include the following
statement:

"Over a time period of many cycles, e.g. one second at MHz
frequencies, the net average energy and the net average power are
related by joules/second. Thus, if certain conditions are met, net
average power can be used to track the net average energy flow based
on the conservation of energy principle. However, at time intervals of
less than one cycle, as exists for instantaneous power, power cannot
be used to track energy because energy is often stored in a reactance,
is not moving at that instant, and is therefore technically not power.
In fact, unlike energy, power often appears and disappears. There are
special cases where average power in joules/second can be used to
track average energy in joules but instantaneous power is not one of
those special cases."
--
73, Cecil, w5dxp.com

Well, you are digging your hole deeper and deeper. You really should
take a pause and try to understand the significance of "Continuity
equations". Do seriously consider Kerchoff's current law as an
example.

...Keith

do you not think that it is telling that there is a current law and a
voltage law, but not a basic power law included in basic circuit
theory? maybe there is a reason for that.

what happens to reflected energy ?
 

On Jul 6, 5:23*am, Keith Dysart wrote:
On Jul 5, 9:57*pm, Cecil Moore wrote:

On Jul 5, 7:44*pm, Keith Dysart wrote:

When, exactly, does the EM wave cease to exist?

I don't know exactly but it will be when DC steady-state has been
achieved, i.e. when electrons are no longer being accelerated or
decelerated.

More evasion. So are now saying there may indeed be an EM wave
present with DC? Even with DC, the electrons are not moving with
constant velocity but hop from atom to atom. Seems like
acceleration and deceleration to me.

...Keith

DC does not an EM wave make... nor does one year make DC, the
summation is infinite, you must wait FOREVER for DC to be achieved and
by then you just won't care any more.

what happens to reflected energy ?
 

On Jul 6, 6:01*pm, K1TTT wrote:
On Jul 6, 12:17*am, Keith Dysart wrote:
On Jul 5, 6:19*am, K1TTT wrote:

On Jul 5, 1:26*am, Keith Dysart wrote:

On Jul 1, 8:53*am, K1TTT wrote:

On Jul 1, 12:37*pm, Cecil Moore wrote:

On Jun 30, 11:29*am, Keith Dysart wrote:

Check the a0 coefficient in the Fourier transform. This represents
the DC component of the signal.

And the result is zero EM waves, either forward or reflected, and your
argument falls apart.

Without this, how would you deal with a signal such as
* V(t) = 10 + 2 cos(3t)

If the cosine term is zero, there are zero EM waves, either forward or
reflected, and your argument falls apart.

Incidentally, V(t) = 10, is a perfect way to prove that energy and the
time derivitive of energy are not the same thing and your argument
falls apart.

Alternatively, one can use the standard trick for dealing with
non-repetitive waveforms: choose an arbitrary period. 24 hours
would probably be suitable for these examples and transform from
there. Still, you will have zero frequency component to deal
with, but there will be some at higher frequencies (if you
choose your function to make it so).

Windowing doesn't generate EM waves where none exist in reality and
your argument falls apart.
--
73, Cecil, w5dxp.com

a better argument is that a constant voltage produces a constant
electric field everywhere, since the field is not varying in time or
space there is no time or space derivative to create a magnetic field
so there can be no propagating em wave. *you could do the same with
zero or constant current producing a constant magnetic field.

The same question for you...

With an infinitely long transmission line excited by a step function,
is there an EM wave propagating down the line?

If not, what is it that is propagating down the line? Especially at
the leading edge?

essentially the dc case IS unique in that you must wait forever for it
to reach sinusoidal steady state since the lowest frequency component
is 0hz

You have used similar phrases before. Are you suggesting that an
open circuited transmission line excited with a step function takes
infinitely long to read steady state?

...Keith

'it depends'... in the special case you have concocted where the

'Concocted has such perjorative ring to it. Much better would be
'appropriately selected to illustrate a point'!

signal source has no reflections it only takes one round trip. *

Excellent. Some agreement.

this
case is very misleading if you try to extend it to cover other cases.
in general it takes infinitely long and you must account for the
infinite series of reflections. *

Of course. But this illustrates one of the benefits of "appropriately
selecting" examples. One can choose examples that do not take forever
to settle and therefore can be analyzed in finite time.

that is why the approximations

To which approximations do you refer?

used
to come up with the sinusoidal steady state solution is so useful, and
exactly why it can not be applied to steps and square waves and other
non sinusoidal constant sources.

Are you suggesting that it is inappropriate to use the reflection
coefficient computed at an impedance discontinuity to predict the
behaviour of a transmission line excited with a 'step, square wave or
other non sinusoidal constant sources"?

and in your infinite line example it never reaches steady state so the
step wave propagates forever

So is this 'step wave' an EM wave, according to your definition of an
EM wave? If not, what would you call it?

...Keith

correct, the 'step wave' is not AN EM wave, it is an infinite
summation of EM waves

Well at least there is no attempt at diversion here.

What is the shape of these EM waves of which there is an infinite
number which sum to a step?

....Keith

what happens to reflected energy ?
 

On Jul 6, 6:02*pm, K1TTT wrote:
On Jul 6, 12:26*am, Keith Dysart wrote:





On Jul 5, 8:33*am, Cecil Moore wrote:

On Jul 4, 8:08*pm, Keith Dysart wrote:

The system I have in mind has ports through which energy can flow in
or out of the system and components inside the system which can
store energy. For such a system, the energy flowing in to ports
of the system minus the energy flowing out of ports *must
equal the increase in energy being stored in the system.

This must be true at all times, or energy is being created or
destroyed; a bit of a no-no.

But you are not tracking energy - you are tracking power. As Roy has
said, there is no requirement that instantaneous power must balance.
Where are the stored energy terms in any of your instantaneous power
equations? How do you handle the difference in dimensions between
energy and power? The only condition for which NET power must balance
is during a time interval in which there is zero NET stored power,
e.g. during one cycle.

I have rev'ed my zero interference article to include the following
statement:

"Over a time period of many cycles, e.g. one second at MHz
frequencies, the net average energy and the net average power are
related by joules/second. Thus, if certain conditions are met, net
average power can be used to track the net average energy flow based
on the conservation of energy principle. However, at time intervals of
less than one cycle, as exists for instantaneous power, power cannot
be used to track energy because energy is often stored in a reactance,
is not moving at that instant, and is therefore technically not power..
In fact, unlike energy, power often appears and disappears. There are
special cases where average power in joules/second can be used to
track average energy in joules but instantaneous power is not one of
those special cases."
--
73, Cecil, w5dxp.com

Well, you are digging your hole deeper and deeper. You really should
take a pause and try to understand the significance of "Continuity
equations". Do seriously consider Kerchoff's current law as an
example.

...Keith

do you not think that it is telling that there is a current law and a
voltage law, but not a basic power law included in basic circuit
theory? *maybe there is a reason for that

Perhaps. What is your explanation?

....Keith

what happens to reflected energy ?
 

On Jul 6, 6:07*pm, K1TTT wrote:
On Jul 6, 5:23*am, Keith Dysart wrote:





On Jul 5, 9:57*pm, Cecil Moore wrote:

On Jul 5, 7:44*pm, Keith Dysart wrote:

When, exactly, does the EM wave cease to exist?

I don't know exactly but it will be when DC steady-state has been
achieved, i.e. when electrons are no longer being accelerated or
decelerated.

More evasion. So are now saying there may indeed be an EM wave
present with DC? Even with DC, the electrons are not moving with
constant velocity but hop from atom to atom. Seems like
acceleration and deceleration to me.

...Keith

DC does not an EM wave make... nor does one year make DC, the
summation is infinite, you must wait FOREVER for DC to be achieved and
by then you just won't care any more

But previously you said the line would settle after one round trip if
the source was matched. How is this consistent with having to wait
forever?

....Keith

what happens to reflected energy ?
 

On 6 jul, 19:07, K1TTT wrote:
On Jul 6, 5:23*am, Keith Dysart wrote:





On Jul 5, 9:57*pm, Cecil Moore wrote:

On Jul 5, 7:44*pm, Keith Dysart wrote:

When, exactly, does the EM wave cease to exist?

I don't know exactly but it will be when DC steady-state has been
achieved, i.e. when electrons are no longer being accelerated or
decelerated.

More evasion. So are now saying there may indeed be an EM wave
present with DC? Even with DC, the electrons are not moving with
constant velocity but hop from atom to atom. Seems like
acceleration and deceleration to me.

...Keith

DC does not an EM wave make... nor does one year make DC, the
summation is infinite, you must wait FOREVER for DC to be achieved and
by then you just won't care any more.- Ocultar texto de la cita -

- Mostrar texto de la cita -

Hello friends:

A few years ago I posted in this newsgroup a doubt from a friend of me
about DC current (such a batery connected to a lamp) radiating EM
waves... It was in topic "Antenna gain question" (2005-10-31). My
answer wold be that classic physics postulate EM radiation from
accelerated charges in closed circuit because charges are under
centripetal acceleration (I though of ciclotron radiation analogy, of
course). My friend Richard Clarke disagreed with my hypothesis and I
archived the issue for a couple of years, (he give me some analogies
with moving cars, I remember...)

Time later I was casually reading some pages from Kraus and I found
the answer! :D: Kraus says: "a charge moving at uniform velocity
along a curved or bent wire it is accelerated and radiates".
The clue was in words "straight wire" , he says: "Electric charge
moving with uniform velocity along a straight wire does not radiate".
then, a DC also must be rectlinear (perhaps it must move on a
geodesic, but I do not know general relativity enough to say it) (*)

(*) "Antennas" John D. Krauss - Second Edition -1997 Page 50.

73 - Miguel Ghezzi - LU6ETJ

what happens to reflected energy ?
 

"lu6etj" wrote
...

D: Kraus says: "a charge moving at uniform velocity
along a curved or bent wire it is accelerated and radiates".
The clue was in words "straight wire" , he says: "Electric charge
moving with uniform velocity along a straight wire does not radiate".

This principle is used today to produce the light in the free electron
laser: http://en.wikipedia.org/wiki/File:FEL_principle.png
S*

what happens to reflected energy ?
 

On 7 jul, 16:55, "Szczepan Bialek" wrote:
*"lu6etj" ...

D: Kraus says: "a charge moving at uniform velocity

along a curved or bent wire it is accelerated and radiates".
The clue was in words "straight wire" , he says: "Electric charge
moving with uniform velocity along a straight wire does not radiate".

This principle is used today to produce the light in the free electron
laser:http://en.wikipedia.org/wiki/File:FEL_principle.png
S*

Yes, very interesting example (and device),

Cecil it is right respect a photon/noise power ratio, even one photon
of 80 m per second it is very below of noise at 1 K, 80 m-quantum/
Noise dB ratio @1 Hz BW = -38 dB.

Respect to DC current EM radiation, In that time Richard bring an
interesting example of 20 kV electron rectilinear beam rendering a
frequency of 34.6 EHz, the calculus it was quite right, but that
frequency it is not EM waves radiated by electrons but a "matter wave'
frequency... (idem with car analogy = not charged and acelerated
cars :) do not radiates EM waves, but may have a matter wave
asociated to them).
For these reasons IMHO I think -as Cecil do-: basic (undergraduated?)
physics books are very useful to helping us to better understand and
enjoy our ham topics.

73 - Miguel

what happens to reflected energy ?
 

"lu6etj" wrote
...
On 7 jul, 16:55, "Szczepan Bialek" wrote:

This principle is used today to produce the light in the free electron
laser: http://en.wikipedia.org/wiki/File:FEL_principle.png

Yes, very interesting example (and device),

Respect to DC current EM radiation, In that time Richard bring an
interesting example of 20 kV electron rectilinear beam rendering a
frequency of 34.6 EHz, the calculus it was quite right, but that
frequency it is not EM waves radiated by electrons but a "matter wave'
frequency... (idem with car analogy = not charged and acelerated
cars :) do not radiates EM waves, but may have a matter wave
asociated to them).

Each waves are the matter waves. The speed is the particles mass dependent.
So in the wire the sound waves travel with the low speed (medium are ions),
and the electric waves (medium are the free electrons) with the extremally
high speed.

For these reasons IMHO I think -as Cecil do-: basic (undergraduated?)
physics books are very useful to helping us to better understand and
enjoy our ham topics.

For graduated is the field math only.
S*

73 - Miguel

what happens to reflected energy ?
 

On 8 jul, 04:44, "Szczepan Bialek" wrote:
*"lu6etj" ...
On 7 jul, 16:55, "Szczepan Bialek" wrote:



This principle is used today to produce the light in the free electron
laser:http://en.wikipedia.org/wiki/File:FEL_principle.png
Yes, very interesting example (and device),
Respect to DC current EM radiation, In that time Richard bring an

interesting example of 20 kV electron rectilinear beam rendering a
frequency of 34.6 EHz, the calculus it was quite right, but that
frequency it is not EM waves radiated by electrons but a "matter wave'
frequency... (idem with car analogy = not charged and acelerated
cars :) do not radiates EM waves, but may have a matter wave
asociated to them).

Each waves are the matter waves. The speed is the particles mass dependent.