"Owen" wrote in message
...
On Sat, 9 Jul 2005 23:17:18 -0400, "Walter Maxwell"
wrote:


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.

Not at all, you are far more eminent that I on this topic, and I
appreciate your review. I am learning from all this.

Apologies for the difficulty in understanding my notation. Some of it
breaks into psuedo programming code.

First, Xo!=0. I don't know what this means.

Not equals.

Second, what does MML stand for in English?

MLL? Matched Line Loss (dB/m)

Third, in 'functions for V, I, Z, etc at z'. Where is 'z'? I cannot
find any
reference to it.

These quantities are a function of z, where z is a position on the
line. The convention that I have used for displacement is that it is
negative towards the generator. When it matters, displacement is in
metres. The z is just used in definition of some functions in Matchcad
(where you see :=), I have used x for position variable in the graphs.

Fourth, 'exp'. Exponent? If so, of what? e?

exp(x) is e to the power of x (For clarity, I shouldn't have written
it that way, it works, but Mathcad understands the meaning of e
superscript x as e to the power of x, as you will see in some of the
expressions, and it is easier to read.)

Fifth, I understand 'x' as distance along the line from the
termination, but
what is 'y'?

In some of the functions, I have written them to calculate some
quantity between two arbitrary points x and y. They are used in the
definition of fuctions (where you see :=). Most of the graphs use 0
for y so they are plotted wrt the load position

Sixth, what is AppLoss? Approximate? Apparent? Applied?

Approximate Loss, and it was incorrectly based on Zo rather than
nominal Zo.

Seventh, 'DLoss'. What is 'D'? Dielectric? Again, what is the 'y' term?
An
ordinate value?

DLoss was equivalent to AppLoss.

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)?

The bar above the variable is the complex conjugate operator.


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, in the models at http://www.vk1od.net/temp/LineLoss.htm , I now
know why there is such a gap between DLoss and LineLoss. You will
recognise AppLoss / DLoss is your Appendix 8 expression, but my rho
function was based on the modelled complex value of Zo (characteristic
impedance), not the nominal value of Zo.

In the second lot at http://www.vk1od.net/temp/reflection.htm ,
AppLoss is equivalent to DLoss and it is based on nominal Zo, W2DULoss
you will see calculates the rho term (though not identified) using
nominal Ro.

Comparing the results with loss calcuated from P(x)/P(y) (the ratio of
the real power at points x and y), the conclusion is that using your
expression with actual Zo is not at all accurate, using it with
nominal Zo is very close. If I force Zo to be real for all modelling,
the results of all methods is exactly the same (within rounding errors
of the order of 10 to the power of -14)

Some of your questions are just about the Mathcad notation (though
that is not too dissimilar to normal handwritten math notation), but
some of it is my expression and usage. Again my apologies for
confusing with too little explanation. I appreciate your review and
comments Walt.

Owen

Thank you, Owen, for kicking aside the roadblocks preventing me from
understanding your math presentation. I get it now, and realize I was a
knothead for being confused.

It is now perfectly clear why one can't get the true answer using my
expressions for calculating loss on the line when using only the nominal Zo
and not the actual Zo when there is loss. I should have known that
intuitively, and why it escaped me is puzzling.

Studying your math approach let me see the light, and for that I thank
you. And thank you also for taking the time to teach me.

Walt

PS--I note from your telephone numbers in your email to me that you are
not located in the US. Also, the name Duffy sounds somewhat British. Are you
in the UK?


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