On Thu, 7 Jul 2005 11:23:24 -0500, (Richard
Harrison) wrote:

Owen wrote:
"Has anuypne a link to or reference to derivation of the formula?"

My 19th edition of the ARRL Antenna Book treats additional power loss
due to SWR on page 24-10.

Richard, I have an 18th edition, and the formula it gives does not
factor in the angle of the reflection, and so is an approximation.

I don't know if that applies to the 19th edition.

Back to my original post, I was not in search of a formula for an
exact solution, nor a reason to want an exact solution, but rather
whether anyone has seen the derivation of Michaels formula quoted in
QST Nov 97.

Thanks for your help.

Owen

--

"Owen" wrote in message
...
On Thu, 7 Jul 2005 11:23:24 -0500, (Richard
Harrison) wrote:

Owen wrote:
"Has anuypne a link to or reference to derivation of the formula?"

My 19th edition of the ARRL Antenna Book treats additional power loss
due to SWR on page 24-10.

Richard, I have an 18th edition, and the formula it gives does not
factor in the angle of the reflection, and so is an approximation.

I don't know if that applies to the 19th edition.

Back to my original post, I was not in search of a formula for an
exact solution, nor a reason to want an exact solution, but rather
whether anyone has seen the derivation of Michaels formula quoted in
QST Nov 97.

Thanks for your help.

Owen

Well, Owen, if you believe the expressions I presented in Reflections 2 are
approximate, then why do I get the correct answers?

Walt, W2DU

On Thu, 7 Jul 2005 18:46:36 -0400, "Walter Maxwell"
wrote:


Well, Owen, if you believe the expressions I presented in Reflections 2 are
approximate, then why do I get the correct answers?

It seems to me that the method requires that rho is not greater than
one (otherwise the denominator (1-rho2**2) becomes negative, which is
a nonsense). This hints that it does not apply in the general case
where rho *can* be greater than 1, and is therefore probably limited
to cases of distorionless line (Xo=0).

To avoid publishing "ugly" maths here, I have put a page up at
http://www.vk1od.net/temp/reflection.htm with a bunch of expressions
for conditions on the modelled line, including functions for power
flow at an arbitrary point, Loss calculated from powerflow at two
points and loss based on your loss formula + matched line loss.

The graphs show the loss from point x to the load, x is 0 at the load
and negative toward the source.

The algorithms produce quite different results. If I ignore Xo (ie
force Zo to be real), then both algorithms produce the same results.

Have I made a mistake in the maths, or in modelling the scenario?

Owen
--

"Owen" wrote in message
...
On Thu, 7 Jul 2005 18:46:36 -0400, "Walter Maxwell"
wrote:


Well, Owen, if you believe the expressions I presented in Reflections 2
are
approximate, then why do I get the correct answers?

It seems to me that the method requires that rho is not greater than
one (otherwise the denominator (1-rho2**2) becomes negative, which is
a nonsense). This hints that it does not apply in the general case
where rho *can* be greater than 1, and is therefore probably limited
to cases of distorionless line (Xo=0).

To avoid publishing "ugly" maths here, I have put a page up at
http://www.vk1od.net/temp/reflection.htm with a bunch of expressions
for conditions on the modelled line, including functions for power
flow at an arbitrary point, Loss calculated from powerflow at two
points and loss based on your loss formula + matched line loss.

The graphs show the loss from point x to the load, x is 0 at the load
and negative toward the source.

The algorithms produce quite different results. If I ignore Xo (ie
force Zo to be real), then both algorithms produce the same results.

Have I made a mistake in the maths, or in modelling the scenario?

Owen

Thanks for responding, Owen, but I'm going to be otherwise occupied until
Saturday, so the fact that I don't respond immediately doesn't mean that I'm
ignoring you.

Walt