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Old February 4th 04, 06:34 PM
Tom Bruhns
 
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Wolfgang K. Meister wrote in message . ..
....
Is this a solution: (?)

a.) connecting a 50 ohm resistor with wires, approx. length of the
total wire length of the Balun, to the Vectronics
total wire length: same as wires on each side of the balun ;-)
b.) note the SWR over the range
c.) connect the Balun with the termination resistor
d.) calculate the difference ?


No, certainly not! It's a complex quantity, R+jX, that determines the
scalar quantity, SWR. If you add two complex quantities, each of
which has a 2:1 SWR, you could come out with a 4:1 SWR, or you could
come out with a 1:1 SWR, or anything in between. So the difference
between two SWR readings will only serve to confuse you.

Also note that it is not just "wires" you are connecting between the
meter and the load, but a transmission line. The spacing of the wires
can make a large difference in the result, especially as they become a
significant fraction of a wavelength long.

If you've tested the SWR meter with a few known loads and it's giving
you the right readings, then I'd say it will probably about as
accurately tell you the SWR of the impedance presented to it by the
balun and whatever load you put on the other side of the balun. If
the SWR meter does not give you the right results with known loads,
then I'd say you are firing shots in the dark.

Cheers,
Tom

(For the purists and nit-pickers, as used above, SWR for any load
impedance Zload is defined as (1+|r|)/|(1-|r|)|, where
r=(Zload-Zref)/(Zload+Zref), and Zref is simply the reference
impedance to which the meter is (assumed to be) calibrated.)
 
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