Tuning of Hydrogen Maser Cavity by Means of a Variable Capacitance Diode

Details are given on a method of tuning a hydrogen maser cavity by means of a variable capacitance diode placed in a loop directly inside the cavity. The design of the loop-in which the varactor is placed, the loop connection to an external dc bias, and a theoretical analysis of the whole loop system (cavity, tuning loop, and coupling loop) are also given.