Single-sideband performance improvements in conventional power tubes

Two areas of recent investigations have resulted in improved single-side band performance with tetrode power tubes. In one case two contracts were undertaken from the military services to upgrade tubes for use in existing communications equipment. Both programs had similar goals: to improve the performance of existing equipment without the need for modifying the equipment. This could only be accomplished by developing power tubes with improved intermodulation characteristics which would plug directly into the equipment. For a U.S. Army transmitter, tube third-order intermodulation products (IM3) were reduced from a level of --22 dg to a typical value of --33 db. The goal of the Navy contract is to develop a tube with an IM3 of less than -28 db (compared with--20 db for the tube presently used).