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It is well-known that one can determine the efficiency of a microwave 2-port by measuring the reflection coefficient /splGamma/1 at the input port when the output port is terminated by a sliding short circuit. The locus of Γ1 is a circle whose radius equals the efficiency η2m for energy entering port 2 when port 1 is terminated in a nonreflecting load. Similarly η1m is the radius of the circle when port is terminated in a sliding short circuit. This note describes a procedure for obtaining, from the same measured data, new reflection coefficients Γ1N and Γ2N, whose circular loci have radii R1N and R2N which give the efficiencies of the 2-port when connected to an arbitrary load of reflection coefficient ΓL. Thus the Γ1 or Γ2 data may be used to obtain the efficiency of the 2-port when terminated in any arbitrary load. The method is potentially more accurate than the 3-point method since errors can be reduced by drawing a circle through many measured points.