Comments on measuring the overall and the depressed collector efficiency in TWT's and klystron amplifiers

Kosmahl and Ramins (1977), who reported results achieved with broadband, high-performance TWT's, augmented with multistage depressed collectors for higher overall efficiency, have pointed out the necessity for accurately measuring and correctly defining the various power terms involved. In view of the now wide-spread use of depressed collectors and reported results, the definitions of tube and collector efficiency are restated and comments are provided on the sensitivity of these terms to various sources of experimental and definitional errors in order to permit a uniform evaluation of collector performance.