An Electronic System for the Tuning of Masers

The automatic tuning of frequency standards gives a method of removing drifts due to cavity pulling. The paper describes an apparatus designed primarily for tuning the hydrogen maser. The apparatus can also be used for tuning other masers such as the rubidium maser. The system incorporates several of the best features of similar devices previously described in the literature. It includes a digital averager which makes possible the use of a reference oscillator less stable than the maser to be tuned. It includes also a digital integrator, solving the usual problem of offsets in standard integrators. Frequency corrections are made either proportionally or by unit steps through a varactor coupled to the maser cavity. The electronics are made almost entirely with TTL digital integrated circuits (type 7400) for low cost, reliability, and availability. Results on the tuning of rubidium and hydrogen masers are given.