The sensitivities of five transistorized nuclear magnetic resonance spectrometers

The sensitivities of five transistorized nuclear magnetic resonance spectrometers have been measured: a Q meter, a Robinson oscillator, a common marginal oscillator, a modified PKW oscillator and a marginal oscillator the limiter of which was placed behind an r.f. amplifier. All the spectrometers except the common marginal oscillator appeared to possess the same sensitivities for all considered oscillation levels and modulation frequencies, provided that the PKW oscillator and the second marginal oscillator are made sufficiently critical. The common marginal oscillator was less sensitive as this spectrometer could not be made very critical, which resulted in a large contribution of the 1/ f noise.