David G. Nagel wrote:

Tom

Have you ever sloshed water in a bowl? If you had you would have seen
wave forms going in both directions. First the initial wave crosses the
bowl then reflects off the side of the bowl and returns in the opposite
direction.
This is the same as an EMF wave in an antenna. No violation of any
principles of conservation, in fact it is demanded of the principle.

Dave WD9BDZ


Dave,

You have highlighted a misconception that is common and a great cause of
confusion in this forum.

Yes, the "waves" can do what you say. However, the "waves" are merely
mathematical descriptions of the underlying physical phenomena. There is
simply no such thing as a "wave" all by itself. Instead there are water
waves, electromagnetic field waves, guitar string waves, sound waves,
and so on.

Nature tends to be single valued, at least in the ordinary classical
world. At any specific point in time and space there is only one value
of current, one value of electric field, one value for the motion of a
particle (water molecule, guitar string molecule, etc.), one charge
density, and so on. These values can and do change with differences in
time and space. However, the physical entities do not have two values at
once in the same time and place.

73,
Gene
W4SZ

Gene Fuller wrote:
... one value for the motion of a particle ...

Now I know you are pulling our legs. We are talking about
*electrons*, Gene, you know that "particle" capable of
going through two slits at the same time and interferring
with itself on the other side?

Please pick out just one electron and tell us what is
its position and velocity.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Gene Fuller wrote:

... one value for the motion of a particle ...


Now I know you are pulling our legs. We are talking about
*electrons*, Gene, you know that "particle" capable of
going through two slits at the same time and interferring
with itself on the other side?

Please pick out just one electron and tell us what is
its position and velocity.

Cecil,

I think I specifically mentioned the "ordinary classical world", but
I'll play along. Why don't you go ahead and measure that electron to
prove that it goes through both slits at once? 8-)

Gene, W4SZ wrote:
"However, the physical entities do not have two values at once in the
same time and place."

You can measure each of the two simultaneous constituents with the right
equipment. A Bird Thruline wattmeter uses a directional coupler to
separate forward direction power from reverse direction power. These are
obbtainable at the same time and place anywhere in a 50-ohm coax line.
Individual volts and amps in each direction are easily calcuable from
the powers indicated in each direction.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Gene, W4SZ wrote:
"However, the physical entities do not have two values at once in the
same time and place."

You can measure each of the two simultaneous constituents with the right
equipment. A Bird Thruline wattmeter uses a directional coupler to
separate forward direction power from reverse direction power. These are
obbtainable at the same time and place anywhere in a 50-ohm coax line.
Individual volts and amps in each direction are easily calcuable from
the powers indicated in each direction.

Best regards, Richard Harrison, KB5WZI


Richard,

You are in luck! This is Burger King day. Have it your way.

73,
Gene
W4SZ

Gene, W4SZ wrote:
"However, the physical entities do not have two values at once in the
same time and place."

Richard Harrison wrote:
You can measure each of the two simultaneous constituents with the right
equipment. A Bird Thruline wattmeter uses a directional coupler to
separate forward direction power from reverse direction power. These are
obbtainable at the same time and place anywhere in a 50-ohm coax line.
Individual volts and amps in each direction are easily calcuable from
the powers indicated in each direction.

That's not true.

The directional coupler in a Bird meter samples the across vector
(voltage) from a capacitive divider and adds it to a sample voltage of
the through vector (current) from a current transformer in a
predetermined ratio. After that sum, the output is rectified.

I can place it in a system with NO standing waves and it will show
standing waves. I can place it in a system with standing waves and have
it show NO standing waves. It does not measure standing waves, it
simply measures the ratio and phase of voltage and current at one point
in the transmission line.

There can NEVER be current flowing at that point in two directions at
the same instant of time, and the Bird does not even contain a system
that samples standing waves.

Now I can build a piece of test gear that does directly read standing
waves, but it requires a line sampling lwength of at least 1/4 wl.
Such a device would be totally independent of the actual operating
impedance, and could read either current or voltage.

The Bird meter is NOT that type of unit.

73 Tom

wrote:
I can place it in a system with NO standing waves and it will show
standing waves. I can place it in a system with standing waves and have
it show NO standing waves. It does not measure standing waves, it
simply measures the ratio and phase of voltage and current at one point
in the transmission line.

Yes, but if it is calibrated for 50 ohms and installed in a 50 ohm
environment, it is indeed accurately reporting forward and reflected
power. It is accurately separating the forward wave energy from the
reflected wave energy. If it weren't, Bird would be guilty of false
advertising.
--
73, Cecil http://www.qsl.net/w5dxp

Tom, W8JI wrote:
"The directional coupler in a Bird meter samples the across vector
(voltage) from a capacitive divider and adds it to a sample voltage of
the through vector (current) from a current transformer in a
predetermined ratio.

That`s close. In the cartridges is a loop terminated in a diode.
Capacitive coupling of the loop to the center conductor of the precision
ccoax supplies the voltage sample. Inductive coupling of the loop
supplies the current sample.

I`ve described operation several times here and once in this thread, so
I won`t repeat it.

SWR is easy to get from the forward and reflected indications of the
wattmeter.

VSWR = 1 + sq.rt. (ref. PWR / for. PWR)
Divided by 1 - sq.rt. (ref. PWR / for. PWR)

Bird supplies a family of VSWR lines on a graph of forward power vs.
reflected power for those who would avoid the calculation. They can also
supply a slide-rule to do rhe same.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Tom, W8JI wrote:
"The directional coupler in a Bird meter samples the across vector
(voltage) from a capacitive divider and adds it to a sample voltage of
the through vector (current) from a current transformer in a
predetermined ratio.

That`s close. In the cartridges is a loop terminated in a diode.
Capacitive coupling of the loop to the center conductor of the precision
ccoax supplies the voltage sample. Inductive coupling of the loop
supplies the current sample.

I`ve described operation several times here and once in this thread, so
I won`t repeat it.


We're all agreed on what happens with the Bird's sampling lines and
detector. The only differences arise from each person's attempt to
condense it all into a couple of sentences, and aren't worth arguing
about.

But Richard cuts it too short when he claims that:
A Bird Thruline wattmeter uses a directional coupler to separate
forward direction power from reverse direction power.

That claim confuses two different things: what the line-loop-detector
hardware physically *does*; and what the indicated results *mean*. The
first of these is agreed; the second is not.

The disagreement is entirely about the interpretation - in other words,
it's about the theory about standing and travelling waves. Richard
habitually misses out this step, which makes it look as if the Bird
wattmeter "proves" the physical existence of forward and reverse
travelling waves of power.

It doesn't. Everything that you see printed on the Bird's meter scale,
and in the Bird literature, represents that company's particular
interpretation of theory about waves on transmission lines. The details
of that theory are *not* agreed within this newsgroup, which means that
- to some people - the two halves of Richard's claim do not join up.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ian White GM3SEK wrote:
The disagreement is entirely about the interpretation - in other words,
it's about the theory about standing and travelling waves. Richard
habitually misses out this step, which makes it look as if the Bird
wattmeter "proves" the physical existence of forward and reverse
travelling waves of power.

Those are traveling waves of *EM energy* where the power is indicated
at a point as the energy flows through that point. Assuming Z0=50 ohms,
the Bird indicates the number of joules per second flowing toward the
load when the slug is in the forward position. Turning the slug around
causes the Bird to indicate the number of joules per second flowing
toward the source.

The only way to have standing waves of EM energy in a transmission
line is to have two EM waves flowing in opposite directions. I have
asked you before to explain how standing waves develop without the
existence of a forward traveling wave and a rearward traveling wave.
Your silence on that subject has been conspicuous by its absence.
Do standing waves appear by magic?

It doesn't. Everything that you see printed on the Bird's meter scale,
and in the Bird literature, represents that company's particular
interpretation of theory about waves on transmission lines. The details
of that theory are *not* agreed within this newsgroup, which means that
- to some people - the two halves of Richard's claim do not join up.

Are you asserting that Bird is engaging in false advertising?
--
73, Cecil http://www.qsl.net/w5dxp