Jim Kelley wrote:
To my way of thinking, rho is entirely dependent upon the impedances,
and the voltages (reflected voltages in particular) are dependent upon
rho. Not the other way around.

Even when the impedances are only V/I ratios? Seems like circular
logic to me. The V/I ratio causes rho which causes the voltage???
--
73, Cecil http://www.qsl.net/w5dxp



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Tom Bruhns wrote:

Cecil Moore wrote:
Does it really hurt anything to remind everyone that +1 at 180 degrees
equals -1 at zero degrees?

No, and I already agreed with that in another posting in this thread.

When a piece of coax is shorted, we can calculate:

rho = (Z1-Z0)/(Z1+Z0) = (0-50)/(0+50) = -1

After that, we can say it really means +1 at 180 degrees but it is
mathematically consistent in either case.
--
73, Cecil http://www.qsl.net/w5dxp



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On Mon, 29 Sep 2003 17:14:38 -0500, Cecil Moore
wrote:
I give up trying to communicate with you

Hi Cecil,

You did that long ago and were in denial only till now.

73's
Richard Clark, KB7QHC

Cecil Moore wrote:

Jim Kelley wrote:
To my way of thinking, rho is entirely dependent upon the impedances,
and the voltages (reflected voltages in particular) are dependent upon
rho. Not the other way around.

The V/I ratio causes rho which causes the voltage???

Nope. Rho is not dependent upon V/I ratios other than those at real
physical impedance discontinuities. I think you know that. V/I ratios
can vary with position along the line and are not constrained to
equalling Z0 or Zl.

I'm curious why you would ask.

73, Jim AC6XG

Cecil Moore wrote:

Tom Bruhns wrote:

Cecil Moore wrote:
Does it really hurt anything to remind everyone that +1 at 180 degrees
equals -1 at zero degrees?

No, and I already agreed with that in another posting in this thread.

When a piece of coax is shorted, we can calculate:

rho = (Z1-Z0)/(Z1+Z0) = (0-50)/(0+50) = -1

After that, we can say it really means +1 at 180 degrees but it is
mathematically consistent in either case.

This has been repeated so frequently of late, without qualification,
that readers may begin to believe that it is true in general.

It is only true for the special case of single frequency sinusoidal
waveforms.

For more complex waveforms (consider square, sawtooth, step, for
example), negation and 180 degree phase shift are not the same
operation.

Since reflection coefficients (at least for lines with approximately
real Z0) work perfectly fine for these more complex waveforms, it
seems unwise to be thinking that negation and 180 degree phase
shift are the same.

For the example above, stick with rho = -1. It will help you solve
more problems that way.

....Keith

Jim Kelley wrote:

Cecil Moore wrote:
The V/I ratio causes rho which causes the voltage???

Nope. Rho is not dependent upon V/I ratios other than those at real
physical impedance discontinuities. I think you know that. V/I ratios
can vary with position along the line and are not constrained to
equalling Z0 or Zl.

Consider the following:

Source---50 ohm feedline---+---1/2WL 150 ohm---50 ohm load

Isn't the 50 ohms that causes rho=0 on the 50 ohm feedline
simply the V/I ratio at point '+'?
--
73, Cecil http://www.qsl.net/w5dxp



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wrote:
It is only true for the special case of single frequency sinusoidal
waveforms.

Which is the general case for a key-down ham transmitter.
--
73, Cecil http://www.qsl.net/w5dxp



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Richard Clark wrote:

wrote:
I give up trying to communicate with you

You did that long ago and were in denial only till now.

You created your own reality based on your feelings. Nobody
else is capable of experiencing it.
--
73, Cecil http://www.qsl.net/w5dxp



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On Mon, 29 Sep 2003 23:19:47 -0500, Cecil Moore
wrote:
You created your own reality based on your feelings. Nobody
else is capable of experiencing it.

Hi Cecil,

See? You haven't given up afterall!

Feelings hmmm? Yeah, I suppose I get pretty emotional over your wild
nonsense of sqrt of 1 could be -1. It's called laughing until your
sides ache (not really, more a chuckle). You need to ride your bike
more and skip the library.

Practice smiling once a day, read an eh posting from Stefano to break
the ice.

73's
Richard Clark, KB7QHC

Cecil Moore wrote:

wrote:
It is only true for the special case of single frequency sinusoidal
waveforms.

Which is the general case for a key-down ham transmitter.

It is indeed the usual case, but limiting your thinking to the
usual case reduces your opportunity for understanding.

Believing too strongly in the usual case will inhibit your
ability to understand when you begin to explore more
general cases. First you will have to unlearn your beliefs.
If you have repeated them to yourself for too long without
understanding their limitations, you can find it very difficult
to let go of them even when they no longer serve.

It is therefore useful to occasionally remind yourself of
the limitations applicable to your assertions.

....Keith