Keith Dysart wrote:

Keith Dysart wrote:
given a black box of
unknown internals but told that its terminals
present -j567 at the frequency of interest,
would you refuse to calculate the length
of 600 ohm line needed to produce 0 ohms?

Though I notice that you still have not
answered the question.

Why would anyone refuse to calculate the length of
600 ohm line needed to produce 0 ohms? I think I
was the first to calculate it at 43.4 degrees.
--
73, Cecil http://www.w5dxp.com

On Dec 16, 1:18 am, Cecil Moore wrote:
Keith Dysart wrote:
Keith Dysart wrote:
given a black box of
unknown internals but told that its terminals
present -j567 at the frequency of interest,
would you refuse to calculate the length
of 600 ohm line needed to produce 0 ohms?

Though I notice that you still have not
answered the question.

Why would anyone refuse to calculate the length of
600 ohm line needed to produce 0 ohms? I think I
was the first to calculate it at 43.4 degrees.

Exactly. Why would anyone refuse?

So the next question is: What is the phase change
at the terminals of the black box?

1) -93 degrees? (previous answer when it was a capacitor)
2) 36.6 degrees? (previous answer when it was 10 degrees of 100 ohm
line)
3) 0 degrees? (previous answer when it was 46.6 degrees of 600 ohm
line)
4) undecidable?
5) undefined?
6) irrelevant?
7) ???

....Keith

Keith Dysart wrote:
Why would anyone refuse to calculate the length of
600 ohm line needed to produce 0 ohms? I think I
was the first to calculate it at 43.4 degrees.

Exactly. Why would anyone refuse?

Nobody has refused so it is a rhetorical question
the meaning of which is obscure.

So the next question is: What is the phase change
at the terminals of the black box?

You list the phase changes at the terminals of the
black boxes. An s-parameter analysis will prove those
are valid values. Have you done that s-parameter
analysis yet?

b1 = s11*a1 + s12*a2

b2 = s21*a1 + s22*a2

The phase shift is the relative phase between b1 and a2.
And also the relative phase between b2 and a1.

1) -93 degrees? (previous answer when it was a capacitor)

I might be wrong about that one. It might instead be
180 - 93, but that would just be a stupid math mistake.
The main thing is that it is different from the other two.

2) 36.6 degrees? (previous answer when it was 10 degrees of 100 ohm
line)
3) 0 degrees? (previous answer when it was 46.6 degrees of 600 ohm
line)

There's nothing wrong with those answers except maybe
a stupid math error. Each condition indeed does have a
different phase shift that can be measured one inch on
the other side of the terminals if one is simply allowed
to make those measurements. If s11 is measured and stamped
on the black boxes, the phase changes can be easily
calculated.

This is an example of how models can get you into trouble.
Not allowing us to look inside the black box doesn't change
the laws of physics and make all the phase shifts the same.
It just means that the phase shifts are unknown and need
to be measured.

Using that same logic, if you were shackled at the bottom
of Carlsbad Caverns, night and day would stop happening
just because you couldn't see it happening.

Do you really expect us to believe that the phase shift
is the same for all the black boxes but changes abruptly
when the reflection coefficients are measured?
--
73, Cecil http://www.w5dxp.com

On Sun, 16 Dec 2007 08:06:18 -0600, Cecil Moore
wrote:

2) 36.6 degrees? (previous answer when it was 10 degrees of 100 ohm
line)
3) 0 degrees? (previous answer when it was 46.6 degrees of 600 ohm
line)

There's nothing wrong with those answers except maybe
a stupid math error.

Stupid math errors must be valid answers then?

On Dec 16, 9:06 am, Cecil Moore wrote:
Keith Dysart wrote:
Why would anyone refuse to calculate the length of
600 ohm line needed to produce 0 ohms? I think I
was the first to calculate it at 43.4 degrees.

So the next question is: What is the phase change
at the terminals of the black box?

1) -93 degrees? (previous answer when it was a capacitor)

I might be wrong about that one. It might instead be
180 - 93, but that would just be a stupid math mistake.
The main thing is that it is different from the other two.

2) 36.6 degrees? (previous answer when it was 10 degrees of 100 ohm
line)
3) 0 degrees? (previous answer when it was 46.6 degrees of 600 ohm
line)

There's nothing wrong with those answers except maybe
a stupid math error. Each condition indeed does have a
different phase shift that can be measured one inch on
the other side of the terminals if one is simply allowed
to make those measurements.

But the rules for black boxes do not allow measurements
on the inside. This is how they help clarify the thinking.

This is an example of how models can get you into trouble.
Not allowing us to look inside the black box doesn't change
the laws of physics and make all the phase shifts the same.

Nor has that been claimed.

It just means that the phase shifts are unknown and need
to be measured.

As you say, the phase shifts are unknown so from
my list of possible answers, I would have recommended
selecting

4) undecidable

but this leads to it also being

6) irrelevant

since the problem can be solved without the information.

....Keith

Keith Dysart wrote:
But the rules for black boxes do not allow measurements
on the inside. This is how they help clarify the thinking.

I've not disagreed about anything happening outside
the black boxes. I am only interested in what is
happening inside so I am getting rid of the black
boxes. They are a silly unnecessary handicap.

since the problem can be solved without the information.

You haven't solved the problem yet with no black box.

--43.4 deg 600 ohm line--+--10 deg 100 ohm line--open
Vfor1--|--Vfor2

What is the phase shift between Vfor1 and Vfor2? I
solved it for you already.
--
73, Cecil http://www.w5dxp.com

Keith Dysart wrote:
But the rules for black boxes do not allow measurements
on the inside. This is how they help clarify the thinking.

So instead of sweeping technical facts under the rug,
you hide them in a black box. In both cases, the only
apparent purpose is to maintain ignorance.

It seems that whatever part of the system you don't
understand, you draw a black box around it so you
don't have to understand it.

So I ask you once again, given the following two stubs:

--43.4 deg 600 ohm line--+--10 deg 100 ohm line--open
Vfor1--|--Vfor2

--43.4 deg 600 ohm line--+--46.6 deg 600 ohm line--open
Vfor1--|--Vfor2

What are the phase shifts between Vfor1 and Vfor2 for
the two cases?
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:


It seems that whatever part of the system you don't
understand, you draw a black box around it so you
don't have to understand it.


Cecil,

Interesting comment, especially since you frequently reference
s-parameter analysis.

A direct quote from AN-95-1, the slide version, is:

Two-port, three-port, and n-port models simplify the input / output
response of active and passive devices and circuits into "black boxes"
described by a set of four linear parameters.

If you deny the legitimacy of "black boxes" do you need to give up the
use of s-parameters?

73,
Gene
W4SZ

Gene Fuller wrote:
A direct quote from AN-95-1, the slide version, is:

Two-port, three-port, and n-port models simplify the input / output
response of active and passive devices and circuits into "black boxes"
described by a set of four linear parameters.

Thank you, Gene. That contradicts what you said before
about the black box not being allowed to have two of
the four terminals on the other side. Play silly games
with the facts and you tend to get caught.

If you deny the legitimacy of "black boxes" do you need to give up the
use of s-parameters?

No, you need to give up your assertion that a four-
terminal black box doesn't have two terminals on
the other side. Your black box and HP's are two
entirely different concepts.

HP puts a black box around a 4-terminal network to
enhance understanding of the contents of the black
box. You put a black box around a stub to promote
ignorance of the contents of the black box.

I have said before. Specify that the black boxes be
supplied with the four measured s-parameters stamped
on them and I can probably tell you which box is which
without even applying a signal.

Or, more logically, forget the black box entirely since
it is totally irrelevant to the subject being discussed.

Exactly what is it that you think you have proved by
using black boxes. Please be specific.
--
73, Cecil http://www.w5dxp.com

Gene Fuller wrote:
Cecil Moore wrote:


It seems that whatever part of the system you don't
understand, you draw a black box around it so you
don't have to understand it.


Cecil,

Interesting comment, especially since you frequently reference
s-parameter analysis.

A direct quote from AN-95-1, the slide version, is:

Two-port, three-port, and n-port models simplify the input / output
response of active and passive devices and circuits into "black boxes"
described by a set of four linear parameters.

If you deny the legitimacy of "black boxes" do you need to give up the
use of s-parameters?

This is simply a diversion to deflect the discussion away from the
sticky questions about "electrical degrees" which his theory is unable
to resolve. Phase reference is another, and we can expect more.

Roy Lewallen, W7EL