Influence of the various factors on the passive hydrogen maser frequency instability

The influence of the thermal noise on the passive hydrogen maser frequency instability is analysed. New dependencies of the frequency instability on the excitation signal parameters are obtained in comparison with the results which were presented in the known publications. The excitation signal phase modulation index and the atom line saturation factor are specified which provide the minimum of the maser frequency instability. The influence of the modulation frequency on the passive hydrogen maser frequency instability is analysed. The influence of fast phase fluctuations of the quartz oscillator on the hydrogen maser frequency instability is discussed. It is shown that unlike the other passive frequency standards not frequency, but phase fluctuations of the quartz oscillator near the even harmonics of the modulation frequency affect the maser frequency instability. This influence is two orders less than for other passive standards. Frequency shifts due to a spurious amplitude modulation of the excitation signal at the frequency modulation Ω, a spurious phase modulation at the frequency 2 Ω, an inaccuracy of the receiver tuning to the signal frequency are calculated