Radar System Engineering

348 THE MAGNETRON AND THE P ULSER [SEC. 10.5
vantage of this method is that sparking may occur within the tuning
arrangement at high pulse powers.
An unsymmetrical type of tuning which has advantages for highpower
operation is shown in Fig. 10”23. The frequency of the single
tuning cavity is changed by distorting the diaphragm. Since the tuning
cavity is tightly coupled to one of the resonant cavities, and since all the
FtQ. 10.21.—Magnetronwith sprocket tuning. The changein frequency is accomplished
by changingthe inductanceof the resonators.
resonant cavities are very closely coupled to one another by the straps,
the oscillating frequency of the entire magnetron is altered. This unsymmetrical
type of tuning distorts the electric field patterns within the
magnetron and therefore limits its effective tuning range to about 6 per
cent. Advantages of the method are its mechanical simplicity and its
ability to handle very high pulse powers. Figure 10.24 shows output
power as a function of tuning adjustment.
Various other tuninz schemes have been tried, and still others will be
devised, but the three t~pes described above represent the basic methods.
Wartime experience with radar demonstrated that tunability was very
desirable but that extreme tuning range was not.