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Old April 17th 07, 05:27 PM posted to rec.radio.amateur.antenna
Cecil Moore[_2_] Cecil Moore[_2_] is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default Analyzing Stub Matching with Reflection Coefficients

Gene Fuller wrote:
I am impressed! That's a pretty fancy o'scope you got. Measurement of
voltages to four significant digits at t = 0 + delta-t is definitely
world-class. That 291.4 ohm line is pretty special as well.


Your non-technical diversions are noted. How about discussing
the technical question that was posed?

The voltages can be viewed on an o'scope. Their magnitudes
agree with the above calculated magnitudes. Do you know
of any reason that those voltages would not obey the
rules of the reflection model? When does a reflection
coefficient of 0.707 not reflect 0.707 of the incident
voltage?

The 291.4 ohm line is chosen to make rho=s11=0.707. My "450"
ohm ladder-line measures to be actually 380 ohms. Nothing
special about 291.4 ohms except that:

(291.4-50)/(291.4+50) = 0.707

We could actually design a feedline with Z0 = 291.4 ohms.
Want me to show you how? :-)

If you don't like that value, use 300 ohms and 51.5 ohms
for the coax. I'm sure between the choices of 50 ohm
coax and 52 ohm coax, there must be a 51.5 ohm coax in
there somewhere.
--
73, Cecil http://www.w5dxp.com