This report describes the effort on a twelve month program supported by the U.S. Navy to demonstrate the feasibility of an electronically-tuned, pulsed, coaxial magnetron oscillator. The emphasis on the program was the development of suitable electronic tuning techniques rather than on tube fabrication to a particular electrical and mechanical specification. The technical approach adopted by Varian utilizes PIN diodes mounted in the stabilizing cavity of a coaxial magnetron to produce tuning. The diodes and associated d.c. bias coupling leads form an LC network that is an RF circuit coupled to the RF fields of the stabilizing cavity. Discrete frequency shifts are obtained by altering the bias conditions applied to the diode. The accompanying change in RF impedance coupled to the stabilizing cavity produces the associated frequency change. This technique is a variant of a PIN diode tuning scheme that had been investigated previously at S-band on a company-sponsored program.