Hi Richard
Please tell me more about melting the finals and a bit more explanation of
what was happening?
tnx
Hank
"Richard Clark" wrote in message
...
On Sun, 05 Jun 2005 21:58:06 GMT, "Henry Kolesnik"
wrote:

In TV broadcasting reflections from the antenna back to the transmitter
will
be reflected by the transmitter to the antenna and the signal will be
rebroadcast albeit at somewhat less power.

Hi Hank,

That would pretty much reveal the SWR if we knew, wouldn't it? If
"somewhat less power" was in 1.2:1 ratio, we wouldn't care so much,
but how would the viewer feel about such service?

Then depending on the length of
transmission line the viewer may see ghosting.

I think we, or another correspondent and I have dealt with that at one
time. At the time I believe it was called "fringing," not "ghosts."
The difference being that what were called ghosts at the dawn of the
TV era were separated by fractions of an inch rather than fractions of
a mm. As such, ghosts couldn't have been originated by anything
shorter than mile length transmission lines that were poorly
terminated at both ends. Instead, ghosts were actually transmission
path length differentials in a multipath situation.

In audio I don't know why and I have run my Collins 30S-1 into ladder line
with a 14 to SWR with no one except me knowing!

Well, if this is meant to be analogous to fringing/ghosting, I suppose
its because a microsecond blur at AF is entirely inaudible. Or are we
speaking of SSTV? However, this begs the question, How did you know?
All the Collins equipment I taught at school didn't come with a SWR
meter. It was wholly unnecessary if you performed the standard
tune-up. Matter of fact, back then the only SWR meter I saw was for
Ham gear. The finals' tank performed every function of matching as
any tuner.

However, with the KWT-6, we did use an external tuner, 180-V1
(although I may have this mixed up with another model), for coax
feedlines. This was more for its automatic feature where the
transmitter could be tuned up with a 50 Ohm load, and the automatic
tuner simply did the job of presenting it with the transformed load.

However, returning to the point of a transmitter rereflecting a
reflection; I know the bare KWT-6 into ladder line employs its tank to
protect its final tubes. Without that safeguard, I have seen plates
melt - something no one here wants to call dissipation lest it be
evidence of an internal resistance. The bare tubes with their native
very hi Z would rereflect like nothing else - and this begs the
observation - how could you get original any power out of them, past
the tremendous mismatch? The tuner/final tank comes back into the
equation, and rereflection goes out the window as a property of the
transmitter and returns to the domain of matching.

If anyone wants to constrain the entire crusade of the rereflecting
transmitter to the tube set feeding ladder line - then feel free to do
so. However, I don't think I've ever seen a mobile tube rig feeding
ladder line - no doubt one day I will. We will probably talk about
efficiency. :-)

73's
Richard Clark, KB7QHC

Roy Lewallen wrote:
Anyone who's interested can find more interesting cases in "Food for
thought - Forward and Reverse Power.txt" at
http://eznec.com/misc/food_for_thought/. And those who aren't
interested, well, you're welcome to believe what you choose. Just don't
look too closely at the evidence.

(*) Anybody fond of the notion that reverse power "goes" somewhere or
gets dissipated in the source or re-reflected back needs to come to
grips with this problem before building further on the flawed model of
bouncing waves of flowing power.

Roy, I have had an article for review into QEX for more than two
months that explains what is missing from your analysis. Unfortunately,
I have not heard a word from QEX since I submitted the article.

So I will introduce a concept new to the field of RF but completely
understood in the field of optics. I actually introduced this concept
three years ago in discussions on r.r.a.a with Dr. Best but I was
apparently unable to convey the concept.

If I ask you what things can cause 100% reflection, I assume you would
list three things: 1. A short-circuit, 2. An open-circuit, and
3. A pure reactance. And that is indeed true for loads upon which a
single wave is incident.

But the field of optics recognizes an additional thing that can cause
100% reflection and that's wave cancellation. If two coherent EM waves
are traveling the same path in the same direction in a transmission
line and they are 180 degrees out of phase, the waves will cancel and
the energy components in the two waves, which must be conserved, will
be 100% reflected in the opposite direction. The following two optics
web pages verify that fact for EM waves: (near the bottom of the pages)

http://www.mellesgriot.com/products/optics/oc_2_1.htm

http://micro.magnet.fsu.edu/primer/j...ons/index.html

What is happening in your "food for thought" assertions is that you
are neglecting the ability of the phenomenon of wave cancellation to
cause 100% reflection of the energy components in the two canceled
waves, something that is well understood in the field of optics.
Dr. Best also neglected to take interference energy into account in
his QEX article on transmission lines.

"Optics", by Hecht asserts that for every incidence of constructive
interference there must be an equal magnitude of destructive
interference to satisfy the conservation of energy principle. (That
is unless the source itself is capable of delivering extra power.)
By the same token, if the source doesn't absorb constructive
interference energy, it must go somewhere else. In a transmission
line with only two directions, there is only one other way it can
possibly go and it becomes a reflection or a re-reflection.

What is happening in your "food for thought" examples is that
destructive interference/wave cancellation between the forward wave
and reflected wave is occurring at your source. That wave cancellation
event is feeding constructive interference energy back into the
feedline which joins the forward wave energy. Your discussions
ignore the effect of interference energy which must necessarily
be conserved.

Your argument goes something like this: I am ignoring the
constructive/destructive interference energy involved in wave
cancellation. Therefore, it never existed in the first place.
That's a petitio principii type of argument.
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

On 6 Jun 2005 02:40:52 -0700, wrote:

However, I don't think I've ever seen a mobile tube rig feeding
ladder line - no doubt one day I will. We will probably talk about
efficiency. :-)

It was done in 1936.
http://web.wt.net/~nm5k/mobile36.jpg
Cover pix from a 1936 QST...Forgot
what month...
But I still think I prefer coax...
Their "ladder line" looked to be a twisted wire feeder.
The call on that vehicle was W9MSY...

Hi Mark,

Hmmm, the picture's kinda small, and the line looks like coax - or
maybe close ladder line. I will take your word for it as it makes my
track record for accuracy complete. :-)

Well, almost complete. Is the guy holding his pinkie to the radiator
measuring efficiency?

As a sidebar, the police were working 160M mobile back then too.
Seems coax was hardly an off-the-shelf item. Think they used ladder
line too? More probably direct feed.

73's
Richard Clark, KB7QHC

Cecil Moore wrote:

Roy, none of my textbook authors think the reflection model
is flawed. Walter Johnson goes so far as to assert that there
is a Poynting (Power Flow Vector) for forward power and a
separate Poynting Vector for reflected power. The sum of those
two Power Flow Vectors is the net Poynting Vector.

Here's my earlier thought example again.

100w----one second long lossless feedline----load, rho=0.707

SWR = (1+rho)/(1-rho) = 5.828:1
Source is delivering 100 watts (joules/sec)
Forward power is 200 watts (joules/sec)
Reflected power is 100 watts (joules/sec)
Load is absorbing 100 watts (joules/sec)

It can easily be shown that 300 joules of energy have been
generated that have not been delivered to the load, i.e.
those 300 joules of energy are stored in the feedline.

Not easy if t 2 sec. :-)

The 300 joules of energy are stored in RF waves which
cannot stand still and necessarily travel at the speed of
light.

It's ironic that the first paramater cited in the problem starts with an
'S'. :-)

TV ghosting can be used to prove that the reflected
energy actually makes a round trip to the load and back.
A TDR will indicate the same thing.

If either source were monochromatic, I bet I could come up with an
example where the surfaces reflect no energy. :-)

Choosing to use a net energy shortcut doesn't negate the
laws of physics.

Particular when characterized as a matter of opinion, it can be like
having a religious discussion.

73 ac6xg

Cecil,

You can't be serious!

This is basic stuff found in virtually any intermediate level E&M textbook.

The treatment is generally the same; start with the field equations
describing the waves, add the material conditions and the boundary
conditions, plug and crank. The answers pop right out. No need to invoke
any magic incantations about interfering waves or wave cancellation. The
interference is the result of the analysis, not the cause.

In the classical case, there is absolutely no difference in behavior
between "RF" and "optical". The material properties for every situation
can vary, but the physical principles do not.

Sooo, rather than introducing a new concept, you are perhaps the last
person to finally understand the old one.

73,
Gene
W4SZ



Cecil Moore wrote:

[snip}

So I will introduce a concept new to the field of RF but completely
understood in the field of optics. I actually introduced this concept
three years ago in discussions on r.r.a.a with Dr. Best but I was
apparently unable to convey the concept.

If I ask you what things can cause 100% reflection, I assume you would
list three things: 1. A short-circuit, 2. An open-circuit, and
3. A pure reactance. And that is indeed true for loads upon which a
single wave is incident.

But the field of optics recognizes an additional thing that can cause
100% reflection and that's wave cancellation. If two coherent EM waves
are traveling the same path in the same direction in a transmission
line and they are 180 degrees out of phase, the waves will cancel and
the energy components in the two waves, which must be conserved, will
be 100% reflected in the opposite direction. The following two optics
web pages verify that fact for EM waves: (near the bottom of the pages)

http://www.mellesgriot.com/products/optics/oc_2_1.htm

http://micro.magnet.fsu.edu/primer/j...ons/index.html


What is happening in your "food for thought" assertions is that you
are neglecting the ability of the phenomenon of wave cancellation to
cause 100% reflection of the energy components in the two canceled
waves, something that is well understood in the field of optics.
Dr. Best also neglected to take interference energy into account in
his QEX article on transmission lines.

"Optics", by Hecht asserts that for every incidence of constructive
interference there must be an equal magnitude of destructive
interference to satisfy the conservation of energy principle. (That
is unless the source itself is capable of delivering extra power.)
By the same token, if the source doesn't absorb constructive
interference energy, it must go somewhere else. In a transmission
line with only two directions, there is only one other way it can
possibly go and it becomes a reflection or a re-reflection.

What is happening in your "food for thought" examples is that
destructive interference/wave cancellation between the forward wave
and reflected wave is occurring at your source. That wave cancellation
event is feeding constructive interference energy back into the
feedline which joins the forward wave energy. Your discussions
ignore the effect of interference energy which must necessarily
be conserved.

Your argument goes something like this: I am ignoring the
constructive/destructive interference energy involved in wave
cancellation. Therefore, it never existed in the first place.
That's a petitio principii type of argument.

On Mon, 06 Jun 2005 15:05:43 GMT, "Henry Kolesnik"
wrote:

Please tell me more about melting the finals and a bit more explanation of
what was happening?

Hi Hank,

Direct observation offered a glowing plasma between the filament and
the plate. It was football shaped rather than beam-like or an
amorphous cloud. One point of the football touched the cherry red
plate. Following a quick power-down, that point on the plate did not
exist anymore as there was a hole. Couldn't really tell, but no doubt
the grid suffered just as much in its own way.

I suppose plates have become more robust over the years since that
amazing demonstration. I helped fix one friend's Amp when it failed
along with his antenna (or t'other way round as the chain of causality
would suggest). His Amp simply quit working suddenly during bad
weather. Fuses checked - OK. No interlocks were open - OK. The tube
looked good at a glance - OK. HV Supply looked good - OK. The
filaments failed to light up - odd, but consistent. Time to crack
open the case. Pulled the tube and measured its filament continuity -
OK. Measured filament supply - OK. Things were really getting
strange. Time to bust the chassis open and really look. There on the
baseplate were several small pools of solder in a circular pattern -
how odd. Close scrutiny of connections revealed bright and soldered
wires to everything - OK. Time to look at the tube again. Every pin
was solder free - that was on the chassis base plate. [dirge played
here] The filaments' wires were making enough contact to measure
continuity, but no where enough to support real power.

In other tubes I've seen the heat become so extreme that the glass
envelope slumped into the vacuum and enclosed the plate structure like
taffy. This didn't even crack the glass (or it had simply re-fused).
Tube still worked afterwards though (so I would suppose the glass
never cracked). One occasion was actually due to a bias problem
created when the cathode load shorted. Lack of bias protection sent
the circuit into massive conduction. Of course the short came about
because of an initial excessive conduction (surprising in its own
right because the common failure mode is to open).

I've also seen stressed thyratrons so mismatched that they filled the
workspace with their purple glow like a floodlight. Thankfully fuses
work as I did not want to be near that final testimony.

Now, that was the short list of Bottle failures. I have another list
of melted state failures too, but their evidence is usually better
hidden and less dramatic - heat sinking generally spreads the risk,
so to speak. And speaking of heat sinks, I've drawn a number of
blisters from those that normally only warmed my hand. Note there
should be emphasis on normally warm and the obvious contradiction with
blisters.

Experience with failure has strongly correlated with heat and
mismatch. Heat was born by resistance. Resistance is part of life
and amplifiers. Heat comes in two forms. Slow-like, which is
generally current based; and sudden, which is generally voltage based.
I've felt along heatsinks immediately following failure that were as
cool/tepid as usual, or ominously cooler! The sudden heat of arc-over
in silicon can destroy just as effectively as the long slow broil of a
plate turning to slag.

Every mismatch in the Amateur experience is a probablistic spin of the
wheel of misfortune. Sometimes the wheel stops on the slow bake that
aborbs into heatsinks and you notice unusual smell, or your fan
running on too long - Quick! do something, and you survive. Other
times there's the snap of finality. Both of these examples are for
those with keen senses, and often failure comes as a whimper.

Most suffers usually discover what matching is for, even if they don't
know how it works.

73's
Richard Clark, KB7QHC

Gene Fuller wrote:
Cecil, You can't be serious!
This is basic stuff found in virtually any intermediate level E&M textbook.

If you can provide me with a reference that says, wave cancellation can
cause reflection of the canceled waves, I will be eternally grateful.
I have been able to find references that imply such for light waves,
but I have not found one that comes right out and says it for either
light waves or RF waves.

I agree with you 100%. I had this "basic stuff" taught to me at Texas
A&M half a century ago. But Roy's "food for thought" stuff completely
ignores exactly that "basic stuff" concerning constructive/destructive
interference. Nowhere in his arguments is "interference" even mentioned.
I expect him to respond that interference is irrelevant. Dr. Best
went so far as to deny that interference is necessary for a Z0-match to
occur in a system with reflections. That was around May/June 2001 on
this very newsgroup for anyone who wants to Google it.

I have been fighting this battle for three years on this newsgroup.
Now you say it's "basic stuff". I've agreed for three years, but
where have you been all this time?

The treatment is generally the same; start with the field equations
describing the waves, add the material conditions and the boundary
conditions, plug and crank. The answers pop right out. No need to invoke
any magic incantations about interfering waves or wave cancellation. The
interference is the result of the analysis, not the cause.

Some people have forgotten what they learned in college. Their net/
steady-state shortcuts have become reality and scrambled their brains.
You are obviously not one of the people at whom I aimed my remarks.
I am glad to see that not everyone has been seduced into thinking
that interference is irrelevant.

In the classical case, there is absolutely no difference in behavior
between "RF" and "optical". The material properties for every situation
can vary, but the physical principles do not.

I know that. You know that. We are on the same side. Now convince the
RF gurus of that. Roy calculated the net power at the source and
assumed from that figure that there was not enough energy available
to support the energy in reflected waves.

Sooo, rather than introducing a new concept, you are perhaps the last
person to finally understand the old one.

No, not the last one. What you say is exactly what is wrong with
Roy's arguments that reflected energy doesn't flow from the load
back toward the source. I am NOT introducing a new concept. I am
introducing a new (or forgotten) concept to some of the RF gurus
on this newsgroup. I am (re)introducing destructive/constructive
interference concepts to Roy, Dr. Best, and others.
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

Richard Clark wrote:
Every mismatch in the Amateur experience is a probablistic spin of the
wheel of misfortune. Sometimes the wheel stops on the slow bake that
aborbs into heatsinks ...

Current maximum, Ifor+Iref in phase. Vtot = |Vfor|-|Vref|

Other times there's the snap of finality.

Voltage maximum, Vfor+Vref in phase. Itot = |Ifor|-|Iref|
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

In my third example, where does the other 10 watts of reflected power
go? If it goes to the load and back, why does it reflect off the source
resistor?

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

(*) Anybody fond of the notion that reverse power "goes" somewhere or
gets dissipated in the source or re-reflected back needs to come to
grips with this problem before building further on the flawed model of
bouncing waves of flowing power.


Roy, none of my textbook authors think the reflection model
is flawed. Walter Johnson goes so far as to assert that there
is a Poynting (Power Flow Vector) for forward power and a
separate Poynting Vector for reflected power. The sum of those
two Power Flow Vectors is the net Poynting Vector.
. . .

I don't see anything on those web pages that's outside the concept of
the ordinary interference of waves, i.e., that they add and subtract
where they occupy the same space. I don't at all see the concept of a
wave of flowing average energy being bounced back or about by another
wave, which is what you're proposing as you have many times in the past.
But then, many people find miracles when I see only coincidence, so I'm
a bit deficient in that regard.

This topic has been previously discussed beyond a tedious degree in this
newsgroup; anyone interested can find it via groups.google.com. I don't
have anything to add to it, with the exception of this question which is
relevant to the topic:

Does your analysis produce the result of 2.3 dB loss claimed by H.
for a 1.7:1 SWR?

Best luck with your QEX article. I look forward to reading it.

Roy Lewallen, W7EL

Cecil Moore wrote:


Roy, I have had an article for review into QEX for more than two
months that explains what is missing from your analysis. Unfortunately,
I have not heard a word from QEX since I submitted the article.

So I will introduce a concept new to the field of RF but completely
understood in the field of optics. I actually introduced this concept
three years ago in discussions on r.r.a.a with Dr. Best but I was
apparently unable to convey the concept.

If I ask you what things can cause 100% reflection, I assume you would
list three things: 1. A short-circuit, 2. An open-circuit, and
3. A pure reactance. And that is indeed true for loads upon which a
single wave is incident.

But the field of optics recognizes an additional thing that can cause
100% reflection and that's wave cancellation. If two coherent EM waves
are traveling the same path in the same direction in a transmission
line and they are 180 degrees out of phase, the waves will cancel and
the energy components in the two waves, which must be conserved, will
be 100% reflected in the opposite direction. The following two optics
web pages verify that fact for EM waves: (near the bottom of the pages)

http://www.mellesgriot.com/products/optics/oc_2_1.htm

http://micro.magnet.fsu.edu/primer/j...ons/index.html

. . .