A general set of standing wave relations, applicable to the rf‐ and i.f.‐substitution techniques, are derived and used in the subsequent development of curves appropriate to measurements made around the pattern minimum. Although the experimental results using the rf‐substitution procedure have not been recorded for a VSWR in excess of 200:1, there appears to be no limit on the magnitude of standing wave ratio that can be measured, if suitable equipment is available. An analysis of errors reveals that the principal factor which influences the accuracy attainable is the precision with which the attenuator can be determined.