On Thu, 13 Oct 2005 14:31:22 GMT, Cecil Moore wrote:

The Bird is in error when it reports the SWR to be 1:1.
This is the poor carpenter blaming his tools. The instrument can only
be valid within its presumed operating conditions. Deliberate misuse
is not a reason to crow about inaccuracy.
The SWR is *NOT* 1:1 anywhere on the load side of the tuner.
This is the poor carpenter asking for his wage for his "craft." The
Bird is accurately responding to the operating conditions it is found
within. The manufacturer of the Bird wattmeter makes no claim as to
the state of match BEFORE the meter; and especially when it is so
obviously and deliberately misused - which in this sliver of
specificity is transparent to the reading.

What is being busted is the claim that a necessary condition of
operation for the Bird was the requirement for a length of 50 Ohm line
to "force" a purely mythical presumption. That myth has been exposed
and discarded.

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Owen,

To respond to your last question:
Has anyone experimental evidence to the contrary?
is consistently NO. Your own time at the bench has already drained
the pool of ability in that regard. Your only expectation ever after
having bellied up to the bench is to watch your work being gummed to
death.

However, for completeness' sake, and as no one here really understands
what accuracy is about anyway, there is one factor to be considered.
The numbers offered verge on the limit of the Bird's ability to
resolve a power anyway. There is a built in probability of ±5W of
error from the get-go, and any snake oil salesman can craft an
argument leveraging that error to prove anything. We have seen that
±5W error in the form of an argument that uses both + and - (not
simply one or the other) to please a theory.

Owen, the same experiment with a deliberate mismatch of 3:1 would be
just as effective at busting the myth AND providing data that
overwhelmed the inherent meter inaccuracy.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

Cecil Moore wrote:
The Bird is in error when it reports the SWR to be 1:1.

This is the poor carpenter blaming his tools.

Exactly! You got my point. It is operators who refuse to
recognize the errors in the Bird's readings and report
a bogus SWR as "correct" who are at fault.
--
73, Cecil http://www.qsl.net/w5dxp

On Thu, 13 Oct 2005 17:27:01 GMT, Cecil Moore wrote:

Richard Clark wrote:

Cecil Moore wrote:
The Bird is in error when it reports the SWR to be 1:1.

This is the poor carpenter blaming his tools.

Exactly! You got my point. It is operators who refuse to
recognize the errors in the Bird's readings

There was no error in the reading beyond the inherent ±5% specified as
the meter movement's. Owen no where at any time makes any appeal to
measuring or presenting SWR so the following claim is entirely
fabricated to present something not under his, my, or other poster's
consideration:

and report a bogus SWR as "correct" who are at fault.

Persistence in wedging a new picture into a valuable frame does not
make it a classic portrait by a master of the craft. This finger
painting being offered is no more notable than yet another tacky Elvis
on velvet.

Richard Clark wrote:

Cecil Moore wrote:
Exactly! You got my point. It is operators who refuse to
recognize the errors in the Bird's readings

There was no error in the reading beyond the inherent ±5% specified as
the meter movement's.

The Bird is supposed to measure power. The Bird's forward
power readings are in error unless used in a 50 ohm
environment.

I previously talked about using a hammer on a screw. I was
hoping even you could understand that metaphor without me
having to explain it to you.
--
73, Cecil http://www.qsl.net/w5dxp

On Thu, 13 Oct 2005 18:48:05 GMT, Cecil Moore wrote:

The Bird is supposed to measure power. The Bird's forward
power readings are in error
That has not been demonstrated by Owen's example. Elvis is getting
moldy, and the velvet is becoming tattered at the frame where it was
nailed in.

Richard Clark wrote:
Cecil Moore wrote:
The Bird is supposed to measure power. The Bird's forward
power readings are in error

That has not been demonstrated by Owen's example.

Richard, if you don't understand why a 50 ohm power meter yields
erroneous readings when installed in a 75 ohm environment, I
don't know what else to tell you. What is it about using a
hammer on a screw that you don't understand?
--
73, Cecil http://www.qsl.net/w5dxp

On Thu, 13 Oct 2005 19:17:23 GMT, Cecil Moore wrote:
you don't understand why a 50 ohm power meter yields erroneous readings
Any error of misunderstanding Owen's post is entirely your own.
My career in calibrating RF Wattmeters while you were flipping bits is
a good indicator of the tectonic trench you stand in.

The fact remains, there has been no error displayed (beyond the casual
5% reading error inherent in the meter) nor his results refuted as to
how much power has impinged upon the cabled load as he explicitly
described being attached to the Bird's measurement port. As there is
no other use for such a wattmeter, any appeals to the contrary are
idle chatter.

Owen's claim stands: the myth of requiring a 50 Ohm transmission line
at the measurement port of the Bird wattmeter has been debunked. This
comes as no surprise but for one poster to this board.

On Thu, 13 Oct 2005 09:53:08 -0700, Richard Clark
wrote:

Owen,

To respond to your last question:
Has anyone experimental evidence to the contrary?
is consistently NO. Your own time at the bench has already drained
the pool of ability in that regard. Your only expectation ever after
having bellied up to the bench is to watch your work being gummed to
death.


I fully expected someone to object, not only to object, but to do so
without any original experimental evidence and to devalue the
experiment that I did so that some readers who do not have even a
meager understanding of transmission line theory fall to being
convinced by whoever is most tenacious is defending their position.

However, for completeness' sake, and as no one here really understands
what accuracy is about anyway, there is one factor to be considered.
The numbers offered verge on the limit of the Bird's ability to
resolve a power anyway. There is a built in probability of ±5W of
error from the get-go, and any snake oil salesman can craft an
argument leveraging that error to prove anything. We have seen that
±5W error in the form of an argument that uses both + and - (not
simply one or the other) to please a theory.

Owen, the same experiment with a deliberate mismatch of 3:1 would be
just as effective at busting the myth AND providing data that
overwhelmed the inherent meter inaccuracy.

Indeed, and I considered a number of other experiments that did so,
but this one was based on components at hand, and should have been
easily understood by a person with the most basic understanding of
transmission line theory. It was important to surround the Bird with
line different to 50 ohms.

I expect the argument to twist an turn, to focus on everything but the
assertions that:
- there should be approximately a 50+j0 Z presented to the load side
terminals of the Bird Thruline (ie the ratio of V/I is 50+j0 where V
is the net or forward and reflected voltages, and I is the net of
forward and reflected currents);
- the Bird Thruline is a 120mm section of 50 ohm transmission line;
- in the region of the Bird Thruline sampler element, the ratio of V/I
is approximately 50+j0;
and that the observed Bird 43 readings were reasonably consistent with
those assertions.

The arguments that knowing that the Bird measurements are valid at the
point of measurement is of little value are unrelated to the issue and
a diversionary tactic, but wrong nevertheless. I won't add to the
diversion to identify them.

I will extract the essence of the analysis and write a separate web
page on it that may in the longer term assist others in their
development, go being "gummed to death" doesn't totally devalue the
information behind the case, and it might just be the cost of exposing
the proposition to review.

Thank you for your support.

Owen

PS: I am planning my next mythbusters (oh no! I hear...) Myth: SWR
meters measure SWR. Now this is not to bag SWR meters, I think that
they are very useful instruments, but they have limitations, and the
greatest problem is not the meters, but probably the knowledge base of
those (ab)using them.
--

Owen Duffy wrote:

The arguments that knowing that the Bird measurements are valid at the
point of measurement is of little value are unrelated to the issue and
a diversionary tactic, but wrong nevertheless.

Hi Owen,

If it's wrong to argue that Bird wattmeter measurements are valid at the
point of measurement, I don't wanna be right. ;-)

PS: I am planning my next mythbusters (oh no! I hear...)

Undoubtedly it's the collective "oh goody!" that you hear.

Myth: SWR
meters measure SWR. Now this is not to bag SWR meters, I think that
they are very useful instruments, but they have limitations, and the
greatest problem is not the meters, but probably the knowledge base of
those (ab)using them.

You must be new around here. :-)

73, ac6xg

On Thu, 13 Oct 2005 15:02:37 -0700, Jim Kelley
wrote:

You must be new around here. :-)

Hi Jim,

Give Owen more credit than that, after all he knows at least one
prolific poster:
I expect the argument to twist an turn, to focus on everything but the assertions

As long as you keep on the message, then that profligacy twists and
turns the postings like yellowing leaves starved of nourishment. A
faint rustle of reality causes them to fall unnoticed to the way-side.

73's
Richard Clark, KB7QHC