Owen, I tried to send this as a reply to you, but your email address was
rejected, so I had to send this to the group. My response appears below your

Walt

"Owen" wrote in message
...
On Wed, 6 Jul 2005 21:23:52 -0400, "Walter Maxwell"
wrote:


If you like, I am saying your approach is valid for lossless lines, it
is also valid for all distortionless lines, but I think it is not
accurate for lines in the general case because it isn't correct if
Xo!=0.

Owen

Owen, if X = 0 there is no attenuation, but you're saying my material is
invalid if X is not 0? I'm sorry, but I'm confused.

Walt, it has just occurred to me that I am using the "actual" Zo, not
the nominal Zo, and I think your rho calc is based on the nominal Zo,
as it will be measured with an instrument presumably calibrated for
nominal Zo.

I have compared the loss calculated by your method (with rho based on
nominal Zo, Zo=Ro+j0) and my method and they are very similar (though
not the same). I have added a function to calculate the loss using
your formula based on nominal Zo and plotted it, along with the
difference to the power based loss calc. They are at
http://www.vk1od.net/temp/reflection.htm .

If your method is based on nominal Zo, rather than the actual Zo, it
is likely to be an approximation, though on this example, it is pretty
close and probably is quite adequate for most practical lines at HF
and above. (The error increases as frequency is reduced (Zo departs
more from nominal Zo).)

Having resolved the apparent inconsistency... I am still in search of
a derivation of the Michaels formula.

Owen

----- Original Message -----
From: "Owen"
Newsgroups: rec.radio.amateur.antenna
Sent: Friday, July 08, 2005 6:08 PM
Subject: Calculating loss on a mismatched line

Hi Owen,

I'm trying to understand your Mathcad presentations, but I've run into some
roadblocks concerning terminology, some of which I'm not familiar with. I
confess my questions prove my ignorance, but that's ok if one's trying to
learn. However, I was using nominal Zo.

First, Xo!=0. I don't know what this means.
Second, what does MML stand for in English?
Third, in 'functions for V, I, Z, etc at z'. Where is 'z'? I cannot find any
reference to it.
Fourth, 'exp'. Exponent? If so, of what? e?
Fifth, I understand 'x' as distance along the line from the termination, but
what is 'y'?
Sixth, what is AppLoss? Approximate? Apparent? Applied?
Seventh, 'DLoss'. What is 'D'? Dielectric? Again, what is the 'y' term? An
ordinate value?
Eighth, in the LineLoss(x,y) = 10log... the identical right-hand terms in
both numerator and denominator, the identical functions of 'e^^ x e^^. what
is the meaning of the bar above the second appearance of 'e'? And above
gamma(x)?

I want to understand your math presentation, Owen, especially when I see
that Loss(x,0 - W2DUloss(x,0) is so small I want to understand what makes
the difference. So I'd appreciate it if you'd set me straight on the points
I made above.

Walt