In article , "Reg Edwards"
g4fgq,regp@ZZZbtinternet,com wrote:

Reflections are functions of TIME, not frequency.

Oliver Heaviside had the right idea long before the invention of the
SWR meter.
-----
Reg, G4FGQ.

Hello, and the present or absence of reflections in the steady-state (no
transients as one would see when the system is first energized) is by
comparison of an impedance (Zx) at a measurement point to some reference
impedance (Zo). This reference impedance can be associated with the
characteristic impedance of a transmission line or some other system
characteristic. If Zx and/or Zo varies with frequency (has a reactive
component) then the RMS amplitude of the voltage/current reflections also
varies with frequency. We use this property to match Zx to Zo at some
frequency by minimizing the measured reflected voltage (or current or
power).

In the steady-state there is one voltage/current (as seen by an RF
voltmeter or ammeter) placed at the measurement point. We need a
directional coupler (part of a Bird model 43) or impedance bridge
(referenced to Zo) inserted at the measurment point in order to partition
the sampled voltage/current into incident (forward) and reflected waves.
I'm not sure exactly what Reg meant. Sincerely, and 73s from N4GGO,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

J. B. Wood wrote:
In the steady-state there is one voltage/current (as seen by an RF
voltmeter or ammeter) placed at the measurement point. We need a
directional coupler (part of a Bird model 43) or impedance bridge
(referenced to Zo) inserted at the measurment point in order to partition
the sampled voltage/current into incident (forward) and reflected waves.

Hi John, one important fact that some people would like to
forget is that the reflected wave can indeed be partitioned
from the forward wave. Some people on this newsgroup argue
that the forward wave and reflected wave are inseparable and
that reflected waves contain no rearward traveling energy.

However a circulator plus load resistor located at the source
will prevent reflected wave energy from being incident upon
the source and will heat up that load resistor in the process
proving that reflected waves are real and do contain energy.

My favorite illustration of such is a one-second lossless
transmission line with reflections. The number of watts in
the forward wave plus the number of watts in the reflected
wave equals the number of joules stored in the line during
steady-state. For instance, if Pfor = 200w and Pref = 100w,
then 300 joules of RF energy exist in the one-second long
lossless line during steady-state.
--
73, Cecil, http://www.qsl.net/w5dxp

In article , Cecil Moore
wrote:

Hi John, one important fact that some people would like to
forget is that the reflected wave can indeed be partitioned
from the forward wave.

Hello, and it would be more correct to say that the forward and reflected
waves are components of a standing wave.

However a circulator plus load resistor located at the source
will prevent reflected wave energy from being incident upon
the source and will heat up that load resistor in the process
proving that reflected waves are real and do contain energy.

Hmm. Don't quite get that. Say an RF voltage source is located at port A
of an ideal 3-port circulator designed for a system (characteristic)
impedance of Zo. A load of ZL terminates port B and a load of Zo is
attached to port C. Now, incident energy from the source at A is
transferred by circulator action to the load at port B. If ZL is not
equal to Zo then reflected energy from port B is transferred to port C
where it is dissipated in the port C termination. None of the reflected
energy originating from port B ever returns to port A in this ideal case
(circulator has infinite isolation). Sincerely,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

Cecil Moore wrote:

Hi John, one important fact that some people would like to
forget is that the reflected wave can indeed be partitioned
from the forward wave. Some people on this newsgroup argue
that the forward wave and reflected wave are inseparable and
that reflected waves contain no rearward traveling energy.

However a circulator plus load resistor located at the source
will prevent reflected wave energy from being incident upon
the source and will heat up that load resistor in the process
proving that reflected waves are real and do contain energy.

Hi Cecil

How much energy is "in the reflected wave" without a circulator load
resistor?

73, ac6xg

Jim Kelley wrote:
How much energy is "in the reflected wave" without a circulator load
resistor?

There's the same amount of energy in the reflected wave
either way, with or without a circulator load resistor.
The reflected wave is incapable of looking ahead and
using its free will to decide how much energy to contain
depending upon its future fate. But that is what some
people would have us believe.

Does your question imply: A reflected wave that is
going to be dissipated in a circulator resistor sometime
in the future contains energy but a reflected wave that
is going to be dissipated after the power is turned off
does not contain energy?

In a one second long lossless transmission line, watts
equal joules. A forward wave of 200 watts contains 200
joules of energy. A reflected wave of 100 watts contains
100 joules of energy. Under such conditions, the source
has supplied exactly 300 joules more than has been
delivered to the load, no more and no less. Conservation
of energy strikes again.
--
73, Cecil, http://www.qsl.net/w5dxp

Cecil Moore wrote:

The reflected wave is incapable of looking ahead and
using its free will to decide how much energy to contain
depending upon its future fate. But that is what some
people would have us believe.

Those are the bad people, evidently.

Does your question imply: A reflected wave that is
going to be dissipated in a circulator resistor sometime
in the future contains energy but a reflected wave that
is going to be dissipated after the power is turned off
does not contain energy?

The question implies that there are issues regarding the flow of
energy which you continue to misunderstand. Your answer confirms this.

In a one second long lossless transmission line, watts
equal joules. A forward wave of 200 watts contains 200
joules of energy. A reflected wave of 100 watts contains
100 joules of energy. Under such conditions, the source
has supplied exactly 300 joules more than has been
delivered to the load, no more and no less.

Is your claim that the above describes the system with, or without,
the circulator load?

73, ac6xg

Jim Kelley wrote:
The question implies that there are issues regarding the flow of energy
which you continue to misunderstand. Your answer confirms this.

So please enlighten me. How does a wave know whether to
carry energy or not depending upon its future fate? It
is my understanding that the power in an EM wave is ExH
no matter what its future fate.

Does a laser beam reflected from an ideal mirror carry any
less energy than the forward beam just because it has been
reflected? If so, how does that not violate the conservation
of energy principle?

In a one second long lossless transmission line, watts
equal joules. A forward wave of 200 watts contains 200
joules of energy. A reflected wave of 100 watts contains
100 joules of energy. Under such conditions, the source
has supplied exactly 300 joules more than has been
delivered to the load, no more and no less.

Is your claim that the above describes the system with, or without, the
circulator load?

Yes, in both cases the voltage reflection coefficient
at the load is 0.707 making the power reflection
coefficient = 0.5, i.e. half the power incident upon
the load is reflected.

The system with the circulator load at the signal
generator has the signal generator supplying 200
watts and the circulator load resistor dissipating 100
watts. 'SGCR' stands for a signal generator equipped with
a circulator and circulator load resistor equal to the
Z0 of the feedline. There's 300 joules of energy in the
feedline during steady-state. 100 watts is dissipated
in the load.

200W SGCR-----one second long feedline-------load
Pfor=200W-- --Pref=100W

The system without the circulator and load consists of
a 100 watt source feeding an ideal autotuner tied to
the transmission line. In this case all reflected energy
is re-reflected by the Z0-matched autotuner. 'SGAT' stands
for a signal generator equipped with an ideal autotuner.
There's 300 joules of energy in the feedline during
steady-state. 100 watts is dissipated in the load.

100W SGAT-----one second long feedline-------load
Pfor=200W-- --Pref=100W
--
73, Cecil, http://www.qsl.net/w5dxp

Cecil Moore wrote:

How does a wave know whether to
carry energy or not depending upon its future fate?

Does a laser beam reflected from an ideal mirror carry any
less energy than the forward beam just because it has been
reflected?

What can be said other than; these questions appear to have been posed
by someone who is struggling to understand some pretty simple concepts.

In a one second long lossless transmission line, watts
equal joules. A forward wave of 200 watts contains 200
joules of energy. A reflected wave of 100 watts contains
100 joules of energy. Under such conditions, the source
has supplied exactly 300 joules more than has been
delivered to the load, no more and no less.

Is your claim that the above describes the system with, or without,
the circulator load?


Yes, in both cases the voltage reflection coefficient
at the load is 0.707 making the power reflection
coefficient = 0.5, i.e. half the power incident upon
the load is reflected.

But, is the latter really more than a mathematical convenience? (You
may recall that 'power' isn't something which actually moves in
physical systems. And being a scalar, it can be tricky to do a proper
vector analysis.) How energy moves is dependent upon factors
throughout the entire system - not just at the load.

The system with the circulator load at the signal
generator has the signal generator supplying 200
watts and the circulator load resistor dissipating 100
watts. 'SGCR' stands for a signal generator equipped with
a circulator and circulator load resistor equal to the
Z0 of the feedline. There's 300 joules of energy in the
feedline during steady-state. 100 watts is dissipated
in the load.

200W SGCR-----one second long feedline-------load
Pfor=200W-- --Pref=100W

The system without the circulator and load consists of
a 100 watt source feeding an ideal autotuner tied to
the transmission line. In this case all reflected energy
is re-reflected by the Z0-matched autotuner. 'SGAT' stands
for a signal generator equipped with an ideal autotuner.
There's 300 joules of energy in the feedline during
steady-state. 100 watts is dissipated in the load.

100W SGAT-----one second long feedline-------load
Pfor=200W-- --Pref=100W

Very inventive. The question was posed without a load on the
circulator, not without a circulator. You still haven't answered that
question. Perhaps you wouldn't mind just considering one system at a
time. No sense changing the variables just to make the solution come
out the way we want. Don't they teach you that you're not supposed to
change horses in the middle of a stream out there in Texas? ;-)

So, since we've obviously been talking about the steady state, what's
with all the weird questions about 'how the wave knows' what's going
to happen in the future?

73, ac6xg

John,

I would like to reply to your question (if that's what it is) but I am
unable to understand what you are saying.

So I leave it to Cecil and Co. to add further to the complications and
confusion.

It's really all very simple.
----
Reg.

In article , "Reg Edwards"
g4fgq,regp@ZZZbtinternet,com wrote:

John,

I would like to reply to your question (if that's what it is) but I am
unable to understand what you are saying.

So I leave it to Cecil and Co. to add further to the complications and
confusion.

It's really all very simple.
----
Reg.

Hello, Reg. What I didn't understand was your statement "Reflections are
functions of TIME, not frequency." That statement immediately invited
conflict with the info contained in my electromagnetics and transmission
line theory texts lining my office bookshelf. I attempted to provide some
clarification and hopefully not insult anyone's intelligence. Sincerely,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337