Studies of a short and long - term stability of an active hydrogen maser with stand alone cavity auto tuning

This paper outlines the evolution of the stand alone cavity auto tuning of the active hydrogen maser using microwave cavity frequency switching technique. Analysis of basic destabilizing factors limiting short- term, long- term frequency stability and phase noise of output signal of this technique is given. The effect of cavity tuning on short and medium term stability characteristics is negligible. Long-term frequency stability of (3÷5) × 10^-16 at averaging time 1÷20 days has been achieved.