Broadband Microwave Frequency Meter

An electronically tunable frequency meter is described for rapidly determining frequency over a wide range. The device depends on paramagnetic resonance in α, α-diphenyl β-picryl hydrazyl. It consists of a two-inch section of coaxial transmission line filled with hydrazyl and placed in a longitudinal magnetic field. Frequencies from 600 mc through X band have been displayed on an oscilloscope by sweeping the magnetic field to 4 kilogauss. Two frequencies 8 mc apart at S band have been resolved and the accuracy for a single frequency is ± 1 mc. The complete system is described and performance in L and S bands discussed.