Correct!
These "couplers" typically measure the voltage at a point on the line
(V1=Vfwd+Vref) and the current (I=Ifwd-Iref). Given a value for Zo they
then generate a voltage V2=I.Zo which is equal to Vfwd-Vref. Adding
V1+V2 then gives 2.Vfwd, and subtracting gives 2.Vref.
SWR is then derived from Vfwd/Vref. It is independent of the source
impedance.
Steve G3TXQ
On 14/12/2013 23:33, Michael Tope wrote:
Yes, but it is normalized to a specific impedance in the sense that
the VSWR bridge is calibrated for a certain Zo. If I put 100 ohm
transmission lines on either side of a VSWR bridge calibrated for 50
ohms and I terminate the load side 100 ohm transmission line with 100
ohms and drive the source side with a 100 ohm source, the bridge will
still read 2:1 VSWR even though both the input and output lines are
matched (i.e. no standing wave on the line).
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