Radio age research, manufacturing, communications, broadcasting, television (1941)

HOW SMALL CAN THEY GET, Since the familiar type 201 of 1920, electron tubes, like many radio components, have become progressively smaller while improving in performance. Sub-miniature tube of 1952 on extreme right. A QUIET revolution in design techniques is taking place in the electronics industry. Representing a dra- matic expansion of a trend dating back to the late 1930s, it has begun to bear fruit in smaller, lighter, more compact, and more flexible devices and equipment— and some challenging possibilities appear on the horizon. Probably the most notable disclosure of progress in this program to date came with RCA Victor's announce- ment of the half-size, half-weight walkie-talkie produced for the U. S. Army Signal Corps. Although some com- ponents were so reduced in size that the use of magnify- ing lenses was required for certain assembly and inspec- tion procedures, the instrument offered twice the range of its larger predecessor, and greater selectivity. This wedding of smaller size with better perform- ance is typical of results being achieved in this program, known to electronics engineers today as "subminiaturi- zation." An extension of the "miniaturization" which preceded it, this polysyllabic title means simply the reduction of electron tubes, parts, and circuits to the minimum size without lowering the standard of per- formance. Subminiature tubes with a volimie of only % cubic inch, for instance, are being made to do the work for- merly allotted to miniature tubes with a volume of 3V2 cubic inches. Tuning coils smaller than a dime in By D. F. Schmit Vice President and Director of Engineering RCA Victor Division diameter replace coils several times as large. Flat, two- dimensional printed circuits do away with wiring problems and replace bulky assemblies. A whole family of Lilliputian parts has replaced the familiar capacitors, resistors, transformers, switches, relays, and sockets of yesterday. The trend to miniaturization began shortly before World War II, but it was the wartime military need for compact units, particularly in the field of airborne com- munications and navigation equipment, that sparked the miniaturization program. The engineer who has worked on Air Force contracts, knowing how much equipment of all kinds must go into an airplane, understands that, ideally, such electronic equipment should occupy no space and have zero weight. Weight and size are critical considerations. Miniaturization was the best answer to this problem. The history of miniaturization dates from the late '30s, when RCA developed and produced miniature coils, a 2-by-3-inch speaker, and four miniature tubes for use in RCA Victor's BP-10 "personal" portable radio. These four small tubes, the first of their kind, were a major factor in reducing portable radios to the tiny "personal" size. They were also the forerunners of the whole held of miniature-tube types which have since found widespread commercial application. Advantages of Smaller Tubes While considerably smaller in size and lighter in weight than conventional tj'pes, these miniature tubes were found in many cases to be superior in performance, especially at the higher frequencies. They also have the advantage of being more flexible in application, and less costly, on the average, than larger types. The new tubes fitted right into the needs of the military during World War II. As a result of military demands, many new types were developed. The coming of commercial television later gave miniatures another tremendous boost in commercial application. For many functions, miniatures work much better at television's higher frequencies than regular tubes, because they are more compact and have reduced radio-frequency losses. Today, miniature tubes account for between 50 and 60 per cent of RCA's receiving tube production. 6 RADIO AGE