Angular-momentum wattmeter for the 8mm waveband

After a brief historical introduction, the theory of the couple arising from angular momentum carried by a circularly polarized wave is discussed, with particular reference to waves in waveguides. The paper goes on to describe the design and construction of an absolute wattmeter based on this effect and operating in the millimetric waveband. A number of sources of error are then enumerated and discussed, and an estimate is made of the probable accuracy of the instrument. Careful comparisons with a dry-load calorimeter of the type described by Carlin and his collaborators shows that the two instruments agree to within the estimated errors.