Revisiting the Power Explanation
 

Keith Dysart wrote:

On Mar 21, 4:30 pm, Dan Bloomquist wrote:

Keith Dysart wrote:

On Mar 21, 3:06 pm, (Richard Harrison)
wrote:

Bird says of its Model 43 Wattmeter: "Experience using the "Thruline"
Wattmeter for transmitter tune-up, antenna matching, etc. (i.e. on
operating problems), shows that the power ratio is as useful in practice
as the VSWR."

One can see reflected power disappear at the transmitter terminals as a
match is made to the transmitter load. That eliminates stress on the
transmitter from reverse power.

I suggest that a more accurate description would read:
"One can see the indication on the meter go to zero at the transmitter
terminals as the match is made to the transmitter load".

Then, you have never matched with a reflection. Without the experience,
how can you make a claim? You have not made the observation yet you
claim what it 'should' be.


I may have misunderstood, but I thought that when Richard said "see
reflected power disappear" he was observing the Bird Wattmeter
mentioned
in his previous paragraph and watching its indication go to zero. If
this
is not what was meant, then I need elaboration.

My mistake. You both said something that is not what happens. I will
assume you are looking for no reflection between a transmitter and a
transmatch. But the source to a transmission line is on the other side
of that transmatch. You will most certainly see a reflected wave if the
end of that transmission line is not terminated into purely 50 ohm load.

Otherwise, I think I said the same as Richard in different (and,
arguably
more precise) words.

I see that. But neither is the case. If you are matching a transmitter
to mis-matched line, the reflection does not go to zero. In fact, the
reflection is a function of the line and termination and is constant.
Nothing you do at the transmitter can change it.


...Keith

Best, Dan.

Revisiting the Power Explanation
 

"Richard Fry" wrote in news:1174511497.343920.155080
@e1g2000hsg.googlegroups.com:

Would any poster in this thread who doesn't "believe in" reflected
power kindly explain how a transmission line can fail upstream of a
serious mismatch anywhere along the the length of that line. If that
doesn't result from the sum of forward and reflected voltage/current,
then (IYO) what is the reason such failures?

Without making any admissions about my beliefs...

A transmission line with mismatched load can be described in terms of
travelling waves, and the voltage and current at a point on the line can
be calculated from the forward and reflected waves.

The voltage at the point may be higher than under matched conditions for
the same load power, and that may cause insulation breakdown.

The current at the point may be higher than under matched conditions for
the same load power, and that would cause higher loss in conductors and
may result in damage.

Don't think that this doesn't occur. I've seen it many times, and had
to find and replace the molten and arced-over components that
resulted.

None of these explanations require designating "reflected power" at a
point, or implying that it is the energy in "reflected power" that is
totally and solely responsible for the physical damage.

Owen

Revisiting the Power Explanation
 

On Mar 21, 5:11 pm, "Richard Fry" wrote:
Would any poster in this thread who doesn't "believe in" reflected
power kindly explain how a transmission line can fail upstream of a
serious mismatch anywhere along the the length of that line. If that
doesn't result from the sum of forward and reflected voltage/current,
then (IYO) what is the reason such failures?

Don't think that this doesn't occur. I've seen it many times, and had
to find and replace the molten and arced-over components that
resulted.

RF

You pose a phonomenon that should be added to the list that
needs to be explained without the use of "reverse power".

And you have done an excellent job of doing so by providing
an explanation that refers only to forward and reflected
voltage and current. Not a mention of "reverse power" in
the explanation..

....Keith

Revisiting the Power Explanation
 

Keith Dysart wrote:

You pose a phonomenon that should be added to the list that
needs to be explained without the use of "reverse power".

Me thinks you are trolling and have no interest in an understanding.

Revisiting the Power Explanation
 

"Owen Duffy" wrote
None of these explanations require designating "reflected power"
at a point, or implying that it is the energy in "reflected power"
that is totally and solely responsible for the physical damage.
___________

I guess you are relying on the fact that there will be no reflected r-f
voltage/
current if there is no incident voltage/current? And no argument, there.

But of course, it is the vector sum of ALL of these that may cause the
transmission line/network/tx failure(s) mentioned in my relevant posts
in this thread.

And so that does NOT prove that reflected power/voltage/current
does not exist, or is unimportant in an r-f system design.

The specifications of a transmission line or other r-f network or circuit
can be chosen with due engineering care to be rated for a defined incident
power applied to a load with a given mismatch to a specific Zo, and with
respect to the carrier frequency, the modulation thereon, the ambient air
temperature/pressure, solar illumination, line pressurization, and other
operating parameters.

These realities are commonly recogniz(s)ed and incorporated by most
commercial designers/evaluators of r-f transmission systems, and as a result
pose no significant problems to them and/or their clients.

But none of this means that r-f reflections do not, may not, or can not
exist -- whether in "ham" systems, or otherwise.

RF

PS: Please edit my email address in replies here so that
it can't accurately be picked up by spammers. I get enough
spam already. Gracias.

Revisiting the Power Explanation
 

On Mar 21, 5:24 pm, Dan Bloomquist wrote:
Keith Dysart wrote:
On Mar 21, 4:30 pm, Dan Bloomquist wrote:

Keith Dysart wrote:

On Mar 21, 3:06 pm, (Richard Harrison)
wrote:

Bird says of its Model 43 Wattmeter: "Experience using the "Thruline"
Wattmeter for transmitter tune-up, antenna matching, etc. (i.e. on
operating problems), shows that the power ratio is as useful in practice
as the VSWR."

One can see reflected power disappear at the transmitter terminals as a
match is made to the transmitter load. That eliminates stress on the
transmitter from reverse power.

I suggest that a more accurate description would read:
"One can see the indication on the meter go to zero at the transmitter
terminals as the match is made to the transmitter load".

Then, you have never matched with a reflection. Without the experience,
how can you make a claim? You have not made the observation yet you
claim what it 'should' be.

I may have misunderstood, but I thought that when Richard said "see
reflected power disappear" he was observing the Bird Wattmeter
mentioned
in his previous paragraph and watching its indication go to zero. If
this
is not what was meant, then I need elaboration.

My mistake. You both said something that is not what happens. I will
assume you are looking for no reflection between a transmitter and a
transmatch. But the source to a transmission line is on the other side
of that transmatch. You will most certainly see a reflected wave if the
end of that transmission line is not terminated into purely 50 ohm load.

Otherwise, I think I said the same as Richard in different (and,
arguably
more precise) words.

I see that. But neither is the case. If you are matching a transmitter
to mis-matched line, the reflection does not go to zero. In fact, the
reflection is a function of the line and termination and is constant.
Nothing you do at the transmitter can change it.



...Keith

Best, Dan

I agree with what you say.

I had made the leap that Richard's configuration was transmitter,
Bird, matching
device as that seemed to be the only way that an adjustment could
bring
the meter on the Bird to zero. If this was not the intended
configuration
then I am completely confused and Richard will need to clarify his
intent.

....Keith

Revisiting the Power Explanation
 

Owen Duffy wrote:
Ah, but that is USENET!

Yep, Love it or leave it. :-)

No one has demonstrated that using equivalent impedances etc is not a
valid analysis of the steady state behaviour.

Negative assertions are usually impossible to prove.
The onus of proof is upon the ones who assert that
reflected waves cease to exist during steady-state.
The distributed network reflection model has yielded
valid results for a century or so. Ramo and Whinnery
go so far as to talk about the forward power flow
vector and the reflected power flow vector. People
trying to discredit that model just haven't accomplished
their goal.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Gene Fuller wrote:
It is interesting that you can be so precise at times and so sloppy at
other times. I very carefully limited my discussion to steady state
conditions, which is what everyone is already talking about in this
case. You then conveniently inject modulation into the mix, completely
ignoring what I said.

*Every* real world system has noise modulation
that can be tracked through the system riding on
the forward and reflected traveling waves. Thus
steady-state is never reached in reality and your
argument is therefore just a mind game.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Keith wrote:
For some years now, you have been arguing the reality of 'reverse
power'.

Nope, for the last few years I have been arguing the
reality of a reverse or reflected EM energy wave. Energy
is what moves and is the essence of an EM wave moving
at the speed of light. All I am arguing is the validity
of the distributed network reflection model, something
that has stood the test of time for a century or so.

But there are some challenges to the premise of 'reverse power':
- where does the 'reverse power' go?
- why does the change in dissipation of a generator when 'reverse
power' changes depend more on the design of the generator than
on the magnitude of the 'reverse power'?

Reflected energy waves obey the principles of conservation
of energy and superposition some of which is discussed in
my WorldRadio energy article at:

http://www.w5dxp.com/energy.htm

I would suggest that you try trodding this path. Make a list of
phenomena that you think are explained by 'reverse power'.

Actually, "reflected energy" rather than "reverse power".
Here is very close to an experiment we did at Texas A&M
during the 50's. We observed the ghosting and the professor
explained reflected energy waves to us.

TVSG-----1000 feet 450 ohm ladder-line---75 ohm TV RCVR

If the TV Signal Generator is not equipped with a circulator
to get rid of the reflected energy wave, ghosts will appear on
the TV RCVR. The ghosts are exactly where they should be if
reflected wave energy exists. How would you explain the
ghosting?

You could start by providing a list of phenomena for which you
think the reality of 'reverse power' is the only viable explanation
and offer a willingness to learn about alternative explanations.

Please see above. And please abandon the words, "reverse
power" in favor of reverse or reflected EM energy wave.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Richard Harrison wrote:
Searching the net for "reflected r-f power" returned over 25,000
examples. Belief in reverse power is obviously common.

Oh yeah, I forgot to tell Keith that I'm not the only
one who believes in the validity of reflected energy.
In fact, I see it every time I look in the mirror.

Also HP Ap Note 95-1 has some interesting things to
say, e.g. "|a2|^2 = Power reflected from the load."
--
73, Cecil http://www.w5dxp.com