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November 26th 04, 07:33 AM

On Fri, 26 Nov 2004 04:19:06 GMT, (Robert Lay
W9DMK) wrote:

What does not
make sense is that the high SWR is supposed to produce outrageous
losses. I don't see values that I can interpret as high losses - quite
the opposite. Maybe I just don't interpret it correctly, but I would
expect it to be several ohms - not 0.57 ohms.

Hi Bob,

Thanx for the explicit results. Now what is needed is the explicit
expectation. I note that you circumspectly describe it as being
ARRL Antenna Book would lead me to believe that the above quarter wave
line would exhibit 20 dB of total losses. In order to get those
numbers the SWR at the load of say 8000 would have to decrease to
1.01:1 at the source end in order to account for 20 dB in losses. (See
the example on page 24-9 of the 17th Edition.)
which is an inference which being an interpretation is open to errors
of mis-interpretation.

Reference Data for Radio Engineers, "Mismatch and Transducer Loss,"
"One End Mismatched," pg. 22-12:
Transducer Loss = A0 + 10 Â· log (Pm/P) decibels
where
A0 = normal attenuation of the line
Pm = power that would be delivered were system matched
P = power delivered to the load

Of particular note is that this is one of my references as to the
nature of Source Z which is often neglected in academic treatments
with the presumption that the engineer has already been schooled in
the nature of Real sources (this may shock some complaisant readers
here). However, this citation offers that explicit lesson in figure
10 and makes use of this commonplace characteristic in illustrations
of Mismatch Uncertainty. They go as far as to explicitly offer a
section entitled "Generator and Load Mismatched." You may wish to
review this treatment as it offers the math that would present the
most loss available in a line, above and beyond the typical charts
offered for line loss (which are confined to both ends being matched).

73's
Richard Clark, KB7QHC

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