Richard Harrison wrote:
Ian White, GM3SEK wrote:
"That statement bears no physical relationship to how this instrument
actually works---."

We`ve been through detailled explanations of how a Bird works. Cecil did
not need to do another. The wattmeter takes actual samples of the
voltages and currents at any single point on the coax. These are
representative of the powers which are moving toward the load and away
from the load. Careful calibration allows indicarions in watts.

An electric current through a speedometer is calibrated to indicate
miles per hour. It works. So does the Bird Wattmeter.

The difference is that nobody is trying to create a complete distortion
of the way a speedometer works.

I am not criticizing the Bird 43 at all. I own one, and use it
regularly. It is a clever concept, well executed and with lots of good
features.

My objection is against the "other Bird 43" - not the real hardware, but
a piece of vaporware that is called a "Bird" but only exists in
someone's imagination. Somehow, this imagined instrument can truly
*measure* how much power is flowing in the forward and reverse
directions, and those measurements can be used to "prove" some point
about transmission line theory.

The real-life Bird 43 cannot do that. Its indications of "forward and
reflected watts" are only printing on the meter scale. They come from
calculations that are totally dependent on transmission line theory, so
they cannot be used to prove anything *about* that subject.

You cannot prove a theory by using evidence that depends on the theory
you're trying to prove. That is just simple logic.

The real Bird 43 is a good and useful piece of test equipment... but
nobody should buy that "other" one.


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

Richard Clark wrote:
The net result is that there is still no
vectoral addition that blacks out the light bulb simply because you
can exhibit "away from and toward directions."

A light bulb does not emit coherent light so your
statement is 100% irrelevant to coherent RF sources
and/or coherent laser sources.
--
73, Cecil http://www.qsl.net/w5dxp


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Richard Harrison wrote:
I`m a lousy typist but tried to make an exact copy of part of the page.
I assume you agree the incident and reflected waves travel in opposite
directions in Terman`s example.

All part of the reflection model. Ramo & Whinnery go so far
as to present separate Poynting vectors for forward and
reflected powers where Pz-/Pz+ is the power reflection
coefficient.
--
73, Cecil http://www.qsl.net/w5dxp


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Richard Clark wrote:
To obtain a complete cancellation it requires identical powers with
identical but opposing phases. You would agree that without this
condition there is no complete cancellation?

What you have described is exactly what happens at a
Z0-match point.
--
73, Cecil http://www.qsl.net/w5dxp


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Richard Harrison wrote:
All points on a wavefront are equidistant from the source and emerged
simultaneouslly so they share the same phase.. From a point source light
bulb we would be in the far field.

The big difference is that a light bulb doesn't emit
coherent light. Coherence is a requirement for
superposition and wave cancellation. The light bulb
example is simply irrelevant to what happens with
a single frequency coherent RF transmitter or a
single frequency coherent laser.
--
73, Cecil http://www.qsl.net/w5dxp


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Ian White G/GM3SEK wrote:
The Bird does not generate a vector cross product. There is nothing
inside the instrument that's capable of doing such a thing.

Didn't say it did, Ian. Using valid assumptions like E/H=Z0
and E-field forward + E-field reflected = E-field total,
the multiplication is performed by a combination of phasor
addition, linear addition, and non-linear scaling. It is
an analog calculator.

The hardware displays readings of detected RF voltages - not power. The
forward/reflected power calibration on the meter scale is an external
calculation, based on transmission line theory.

Yes, based on samples of a voltage proportional to the E-field
and samples of a current proportional to the H-field. Given the
basic assumptions of the Bird, it can be proven mathematically
that the Bird is displaying E-field x H-field for forward power
if the slug arrow is pointed in the forward direction and
displaying E-field x H-field for reflected power if the slug
arrow is pointed in the reflected direction.

You know exactly how instruments like the Bird work, because at various
times you have posted accurate descriptions here. Your enthusiasm for
your pet theory is making you distort the truth.

The Poynting Vector is ***NOT*** my pet theory, Ian, it is
mainstream RF engineering.

All I am saying is that the Bird samples a voltage proportional
to the E-field and samples a current proportional to the H-field.
It then performs analog calculations on those parameters.
If you think you can disprove that statement, be my guest.
--
73, Cecil http://www.qsl.net/w5dxp


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Richard Clark wrote:
Entirely ignoring all these other trivial details, that cancellation
is incomplete in and of necessity for real or imagined initial
conditions.

That's not true, Richard. If zero reflected energy reaches the
source in a system with reflections, a Z0-match has been
achieved. For a Z0-match to be achieved, 100% wave cancellation
is necessary. For all the nearly perfectly Z0-matched systems
out there, near perfect wave cancellation of reflected waves
has been achieved.
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil Moore wrote:
Ian White G/GM3SEK wrote:
The Bird does not generate a vector cross product. There is nothing
inside the instrument that's capable of doing such a thing.

Didn't say it did, Ian. Using valid assumptions like E/H=Z0
and E-field forward + E-field reflected = E-field total,
the multiplication is performed by a combination of phasor
addition, linear addition, and non-linear scaling.

As you begin to admit when challenged, the instrument itself does
nothing but add or subtract RF voltages derived by sampling the line
voltage and current. No multiplication is involved.

The calibration to indicate power is performed ENTIRELY on the meter
scale. But the instrument didn't do the multiplication or the I^2R
calculation, so it didn't actually measure power.

It is
an analog calculator.

No, it isn't. The guy who drew the meter scale did the power
calculation. The instrument itself is incapable of multiplying anything.


All I am saying is that the Bird samples a voltage proportional
to the E-field and samples a current proportional to the H-field.
It then performs analog calculations on those parameters.
If you think you can disprove that statement, be my guest.

Ah, the old bait and switch trick.

In your earlier statement you said it "performs multiplication", which
is totally false. But for your final paragraph you've switched it to
"analog calculations", which is more general and thus partly true; and
then you invite me to disprove that.

Cecil, I don't think you even realise you're pulling these dishonest
debating tricks... but after too many years to count, I just don't have
any more time for them.

plonk



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

Richard Clark wrote:
"Actually that is quite wrong. IR is not heat."

He got me. According to Lincoln`s Industrial Reference, from a 100-watt
MAZDA lamp the amount of energy emanating as light is 10%, and as
infrared is 72%. The rest is lost to gas end loss, etc. The loss would
be only 18% You can`t see infrared. The eye is most sensitive to a
yellow-green color around 5550 Angstrom units. Lamps are made to
emphasize white or "daylight" which is rated at about 2400 to 3100
degrees Kelvin.

Best regards, Richard Harrison, KB5WZI

Ian White G/GM3SEK wrote:
Cecil Moore wrote:

Ian White G/GM3SEK wrote:

The Bird does not generate a vector cross product. There is nothing
inside the instrument that's capable of doing such a thing.


Didn't say it did, Ian. Using valid assumptions like E/H=Z0
and E-field forward + E-field reflected = E-field total,
the multiplication is performed by a combination of phasor
addition, linear addition, and non-linear scaling.


As you begin to admit when challenged, the instrument itself does
nothing but add or subtract RF voltages derived by sampling the line
voltage and current. No multiplication is involved.

The calibration to indicate power is performed ENTIRELY on the meter
scale. But the instrument didn't do the multiplication or the I^2R
calculation, so it didn't actually measure power.

It is
an analog calculator.

No, it isn't. The guy who drew the meter scale did the power
calculation. The instrument itself is incapable of multiplying anything.


All I am saying is that the Bird samples a voltage proportional
to the E-field and samples a current proportional to the H-field.
It then performs analog calculations on those parameters.
If you think you can disprove that statement, be my guest.


Ah, the old bait and switch trick.

In your earlier statement you said it "performs multiplication", which
is totally false. But for your final paragraph you've switched it to
"analog calculations", which is more general and thus partly true; and
then you invite me to disprove that.

Cecil, I don't think you even realise you're pulling these dishonest
debating tricks... but after too many years to count, I just don't have
any more time for them.

plonk




Another day, another plonk. Repent! Cecil, before everyone plonks
you.
73,
Tom Donaly, KA6RUH