Abstract
An amplitude‐modulated crystal oscillator to be used in conjunction with a Varian HR60 NMR spectrometer system has been developed for heteronuclear magnetic double resonance. It can be operated at frequencies from 3 to 50 Mc with a stability of about 1 part in 108 over a 5‐min interval. The oscillator will transmit a useful rf magnetic field of at least 0.1 G to the NMR probe.