Tom Ring wrote:

Richard Clark wrote:

Hi Ian,

Perhaps in this immediate thread. However, I have demonstrated both
sides coming to the same conclusions several many times, and one
example as recently as within this last week.

This issue is not about being right, it is about ego foremost else why
all the debate? Hank has asked a fairly straightforward question
with rather simple terms he could accept as a compelling case. To
this point (some 22 entries) that has been largely abandoned with each
scribbler answering their own imagining of how to discover the
philosopher's stone.

73's
Richard Clark, KB7QHC


I haven't been here terribly long, maybe 6 weeks, but I have noticed
that your comment applies to around half of the threads longer than 4 or
so comments.

A better ratio than many newsgroups, and people seem to have a sense of
humor, which a lot of other newsgroup's participants decidedly do not.
So, all in all, it could be worse.

That's very true, Tom. Even with the egos, the civility level is
pretty high in here. Of course that is probably why the fringe elements
don't hang out here.

- Mike KB3EIA -

Hank:

Aren't you confusing the reflections that a TV signal experiences when
it bounces off nearby buildings and structures (causing ghosts) with
transmission line refections -- two entirely different things.

Al


"Henry Kolesnik" wrote in message om...
If this old mind recalls correctly a TV station with an undesireable SWR
will not transmit a clear image to its viewers because the delayed
re-reflection arrives at the TV set later and casues a ghost or smear.
Could you please explain the "Reflected power is a mere fiction." and the
smear or ghost?

tnx
Hank WD5JFR
"Reg Edwards" wrote in message
...

"Richard Clark" wrote:
What you describe as reflection and re-reflection occurs between the
mismatched antenna and the tuner that has been adjusted to minimize
power returned to the transmitter. The sole function of the tuner is
to keep this power from being dissipated by the transmitter (common
experience of arcing, denoting a voltage reflection, or thermal
runaway, denoting a current reflection). The "virtual" reflection
(offered by the tuner) is generally know as the complex conjugate of
the remote load, seen at the near end of the line through which it is
returning. This means that the line transforms the phase and
amplitude of the reflection, and the tuner's job is to invert that
relationship to counteract it, and return it to the antenna.

There are both wave descriptions of this process, and lumped circuit
equivalents. Both work, and both describe the same process from
different points of view. One does not negate the other's validity
(unless, of course, you attempt to mix the points of view and demand
consistency in terms - a frequent rhetorical trap here).

There will no doubt be a flurry of denials to this simple example with
contortions of logic to match. As for the math, you will find it by
the reams, once you've been overwhelmed with the arcana of hyperbolic
descriptions of a novel physics that have to proceed its proof.

Keep your eye on how your literal points in your question go abandoned
with these arcane theories.

73's
Richard Clark, KB7QHC
====================================

Dear Richard, you are confusing the matter even further, if that were
possible.

The only saving grace about your tedius message is that you yourself
eventually realise what a load of overcomplicated nonsense it is.

Reflected power is a mere fiction. Power which is not radiated from an
antenna never actually arrives there. In fact it never leaves the
transmitter.

All the power which leaves the transmiter is radiated except for that
which
is lost in the line. It has nowhere else to go!

But for the existence of so-called SWR meters, the words 'forward and
reflected power' would never enter people's vocabularies. For the few who
become involved with such matters, the misleading fiction also appears in
the language of mathematics.

Names have to be invented in order to discuss mathematical equations in
plain English. But there's no reason why they should be propagated, just
to
confuse, into the real World.

The sole purpose of an SWR meter is to indicate whether or not the
transmitter is loaded with 50 ohms.
----
Reg, G4FGQ

It usefully indicates the vector sum of two voltages
proportional to the net voltage and net current. It
also usefully indicates the vector difference of the
two voltages proportional to the net voltage and net
current. Those are extremely useful indications for
the initiated. I agree it is not very useful for the
uninitiated. I trust that doesn't include you.
--
73, Cecil


An SWR meter does NOT usefully indicate the vector sum of two voltages or
the vector difference between two voltages. I've never seen a meter with
such scales.

Even if it did, of what possible use would it be to anyone who is already
reliably informed his transmitter is loaded with 50 ohms.
----
Reg, G4FGQ

On 23 May 2004 19:02:20 -0700, (alhearn) wrote:

Hank:

Aren't you confusing the reflections that a TV signal experiences when
it bounces off nearby buildings and structures (causing ghosts) with
transmission line refections -- two entirely different things.

Al

Hi Al,

No, he has it correct. There is no material difference between the
two except for the velocity constant (which has no bearing on the
matter).

73's
Richard Clark, KB7QHC

"Cecil Moore" wrote in message
...
Tam/WB2TT wrote:
It shows the composite voltage waveform, and the net current. Exactly
what a
Bird wattmeter would do.

That's not what a Bird wattmeter does. A Bird wattmeter possesses
a directional coupler.

Sort of. I have built circuits that subtract out the transmitted signal,
leaving the received signal.signal. The Bird is cruder than that.

SPICE apparently does not.

I was driving it with a sine wave, but did a transient analysis. The whole
point is it does not have to know about reflections. It calculates the
waveform by using the same rules that are used to derive standing waves and
reflections.

Is it possible
to add a directional coupler to SPICE?

I have built a SPICE model of a Kenwood power/SWR meter (Have better
schematic than for a Bird). Actually, an idealized version that is not
physically realizable; I did this on purpose. Clearly shows what the
limitations are. Interesting thing is that there is information present that
no SWR meter that I know of displays. For an SWR other than 1:1, you can
deduce whether RL is bigger or smaller than Z0 by comparing two voltages.


If you know the Z0, the net
voltage/current magnitudes/phases, it should be possible to use
phasor addition/subtraction to obtain the forward and reflected
components, just like the Bird wattmeter does.

But there is only one voltage sample, which is the sum of Vf and Vr. There
*are* two current samples, but they are exactly the same, only one is 180
degrees out of phase due to looking at the opposite end of the current
transformer.

Here is what happens. Say you want a meter that shows 100W full scale when
feeding a 50 Ohm load. That is 70.7 V and 1.414 A. In the "Forward"
direction this leads to

100 = 70.7K1 + 1.414K2

In the "Reverse"direction, we know that Pr=0, so

0 = 70.7K1 - 1.414K2 ( The minus sign comes from reversing the current
reading).

You have 2 equations, so you can solve for K1 and K2. You know it can't
*really* measure power, because there is no multiplier. Just like the Bird,
it *adds* (vector wise) voltage and current.
--
73, Cecil http://www.qsl.net/w5dxp



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Reg Edwards wrote:
An SWR meter does NOT usefully indicate the vector sum of two voltages or
the vector difference between two voltages. I've never seen a meter with
such scales.

That's the way a Bird wattmeter works. The vector sum of two
voltages is the forward power on the scale. The vector difference
of those same two voltages is the reflected power on the scale.
One voltage is proportional to the net voltage. The other voltage
is proportional to the net current.

Even if it did, of what possible use would it be to anyone who is already
reliably informed his transmitter is loaded with 50 ohms.

In addition to my 50 ohm SWR meter, I have 450 ohm and 300 ohm
SWR meters, Reg. They indicate the forward/reflected powers and
SWR on the antenna side of the tuner which I find most helpful.
--
73, Cecil http://www.qsl.net/w5dxp



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Tam/WB2TT wrote:
You have 2 equations, so you can solve for K1 and K2. You know it can't
*really* measure power, because there is no multiplier. Just like the Bird,
it *adds* (vector wise) voltage and current.

Exactly, and if you work out the math, you will find it yields
a meter deflection that can be calibrated in watts of forward
or reflected power.

In your example, assume that 70.7v yields a 5v sample and 1.414a
yields a 5v sample. If they are in phase, 10v will indicate 100
watts forward and zero volts will indicate zero watts reflected.
If they are not equal and not in phase, their sum still indicates
forward watts and their difference still indicates reflected watts.
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Dave wrote:

Cecil wrote:
Uhhhh Dave, the original topic is the Subject: line. If anything,
what happens inside a transmitter is the irrelevant subject since
appreciable reflections hardly ever reach the typical ham transmitter.

here is the original:

Are you saying that the original subject was wrong?

no, only that you ignored the body of the message and answered what you
wanted to discuss instead of what was asked.


of course it is contrived. no one uses loads of those exact impedances,
or
lengths of coax like you do.

Dave, have you ever heard of an example? What I posted is one
easy-to-understand example of virtually an infinite number of
possible examples of a Z0-match. If you like, here is another
example of a Z0-match:

XMTR------tuner---unknown length of feedline---unknown load
100W--
--0W

There is a Z0-match at the input of the tuner. All the voltages
and all the currents are very close to in-phase or 180 degrees
out of phase at the input of the tuner. Do you have the balls to
assert that the above configuration is "contrived"?

nope, that is a real world situation, but not the one under discussion.


THE GREAT MAJORITY OF AMATEUR RADIO ANTENNA SYSTEMS ACHIEVE CLOSE
TO A Z0-MATCH!!! That means all the voltages and currents are close
to being in phase or 180 degrees out of phase. I'm sorry that technical
fact hairlips you. Since your hidden agenda is hidden, I can only
guess what it might be.

so which is it, in phase or 180 degrees out of phase???

SWR ghosts are usually smear because the transmission line is short and the
displacement fo the image is small compared to object reflection shost which
have a greater image displacement becasue the reflected signal travels over
a greater distance.
73
Hank WD5JFR
"alhearn" wrote in message
om...
Hank:

Aren't you confusing the reflections that a TV signal experiences when
it bounces off nearby buildings and structures (causing ghosts) with
transmission line refections -- two entirely different things.

Al


"Henry Kolesnik" wrote in message
om...
If this old mind recalls correctly a TV station with an undesireable SWR
will not transmit a clear image to its viewers because the delayed
re-reflection arrives at the TV set later and casues a ghost or smear.
Could you please explain the "Reflected power is a mere fiction." and
the
smear or ghost?

tnx
Hank WD5JFR
"Reg Edwards" wrote in message
...

"Richard Clark" wrote:
What you describe as reflection and re-reflection occurs between the
mismatched antenna and the tuner that has been adjusted to minimize
power returned to the transmitter. The sole function of the tuner
is
to keep this power from being dissipated by the transmitter (common
experience of arcing, denoting a voltage reflection, or thermal
runaway, denoting a current reflection). The "virtual" reflection
(offered by the tuner) is generally know as the complex conjugate of
the remote load, seen at the near end of the line through which it
is
returning. This means that the line transforms the phase and
amplitude of the reflection, and the tuner's job is to invert that
relationship to counteract it, and return it to the antenna.

There are both wave descriptions of this process, and lumped circuit
equivalents. Both work, and both describe the same process from
different points of view. One does not negate the other's validity
(unless, of course, you attempt to mix the points of view and demand
consistency in terms - a frequent rhetorical trap here).

There will no doubt be a flurry of denials to this simple example
with
contortions of logic to match. As for the math, you will find it by
the reams, once you've been overwhelmed with the arcana of
hyperbolic
descriptions of a novel physics that have to proceed its proof.

Keep your eye on how your literal points in your question go
abandoned
with these arcane theories.

73's
Richard Clark, KB7QHC
====================================

Dear Richard, you are confusing the matter even further, if that were
possible.

The only saving grace about your tedius message is that you yourself
eventually realise what a load of overcomplicated nonsense it is.

Reflected power is a mere fiction. Power which is not radiated from
an
antenna never actually arrives there. In fact it never leaves the
transmitter.

All the power which leaves the transmiter is radiated except for that
which
is lost in the line. It has nowhere else to go!

But for the existence of so-called SWR meters, the words 'forward and
reflected power' would never enter people's vocabularies. For the few
who
become involved with such matters, the misleading fiction also appears
in
the language of mathematics.

Names have to be invented in order to discuss mathematical equations
in
plain English. But there's no reason why they should be propagated,
just
to
confuse, into the real World.

The sole purpose of an SWR meter is to indicate whether or not the
transmitter is loaded with 50 ohms.
----
Reg, G4FGQ

TV Ghosting (quotes below)

To elaborate, the visibility of a ghost image in analog TV systems is
related to the magnitude, phase and time displacement of the RF reflection
that produced it as compared to the original, or non-reflected waveform.

The round-trip transit time from the TV tx output to the mismatch in its
antenna system will determine the time displacement of the ghost, at the
rate of 1 microsecond of displacement per ~490 feet of distance between the
tx and the reflection plane (vp = 0.997c).

The visible part of a TV image is scanned onto the display screen at a
horizontal rate of about 1 line per 50 microseconds.* An internal
reflection from a transmit antenna connected to the tx by 1,000 feet of
transmission line will create a ghost image ~1 microsecond after the main
image -- or ~1/2" to the right side of it in a 25" wide picture. As the
narrowest vertical line that can be viewed on a display using a 4MHz video
bandwidth is a bit less than 0.35 microseconds wide, a ghost image of it
displaced by 1 microsecond is clearly and separately visible on a 25" wide
display, and will not appear as a "smear" of the main image.

Ghosts also can be produced by external reflections of the radiated TV
signal from buildings, large signs, etc. Often these ghosts have much
greater displacement from the main image than those that can be transmitted
from reflections in the TV transmit antenna system. This is the result of
the greater transit time for those reflections w.r.t. the direct ray, that
are common for reflecting and scattering surfaces where located in the
propagation environment.

Reflections with "short" time displacements are more difficult to resolve
separately as ghosts, but still affect and limit the visual quality of the
TV image. Reflections 40dB or more suppressed from the main image have no
practical, visible affect on it -- regardless of their time displacement.

R. Fry, RCA Broadcast Field Engineer 1965-1980

*allows for the H&V sync pulse intervals and some overscan

_______________________

R. Fry wrote
A 1.3:1 antenna SWR at the far end of more than
about 500 feet of otherwise matched transmission
line connected to that same transmitter WILL produce
a visible ghost.

"Cecil Moore" responded
Of course, a different-cycle reflection is what causes ghosting.