The klystron power amplifier is the transmitting tube in most high-power synthesis systems. It is common that references to such systems are as klystron systems, rather than synthesis systems, but the distinction, synthesis, encompasses all possible methods, including travelling-wave tubes, hard tubes (such as tetrodes, in below-microwave radar), twystrons, and solid-state transmitters, as those used in the ARSR-4. The klystron power amplifier is often called, the klystron drift tube, but the proceeding discussion will reveal that the drift tube is really only a part of the klystron power amplifier.

Although this author believes it is important that the technician understand the basic internal function of all components, it may be even more important for the klystron-radar technician to understand his transmitting tube, than for the magnetron-radar technician to understand his. The klystron requires tuning, and tuning demands an understanding of rudimentary theory, to prevent damage to the very expensive tube.

See figure 10 15. This illustration is of a hypothetical three-cavity klystron, the type used successfully, and very reliably, since the 1950 s, in the joint-use USAF-FAA AN/FPS-20, and its descendants, including the FPS-64, -65, -66, and -67. The major components are (1) a cathode and filaments, (2) an input-and- buncher cavity, (3) an intermediate cavity, (4) an output cavity, and (5) a collector. Latter-day klystrons contain more cavities to provide for both higher power and greater bandwidth. Not shown is a large, external, focus coil(s), or focus solenoid, essential to the klystron operation. The tube will...