The Raytheon CK547DX is an extremely small subminiature pentode vacuum tube, one of the tiniest amplifying tubes ever mass-produced. Developed in the early 1950s, it was designed for ultra-compact, high-reliability applications in military, aerospace, and early portable electronics. In the MicroBasement, the CK547DX represents the absolute limit of vacuum tube miniaturization — a device so small it looks almost like a transistor, yet still a true glass vacuum tube. This write-up covers the history of Raytheon, the CK547DX tube, its function, specifications, time period of use, and legacy.
Raytheon was founded in 1922 in Cambridge, Massachusetts, as the American Appliance Company, initially producing rectifiers and vacuum tubes. It grew rapidly during WWII, producing magnetrons for radar and millions of tubes for military radios. Post-war, Raytheon became a leader in subminiature tubes for portable military gear and early electronics. The company also pioneered semiconductors and microwave technology. Raytheon remained a major defense and electronics contractor until mergers in the 1990s–2000s (now part of RTX Corporation). Its subminiature tubes are prized by collectors for their rarity and engineering ingenuity.
The CK547DX is a subminiature pentode — a five-element tube (control grid, screen grid, suppressor grid, cathode, anode) in a tiny glass envelope with flying leads (no base). It was part of Raytheon’s CK series of subminiature tubes developed for military and aerospace use in the early 1950s. The tube is incredibly small (about 0.3 inches in diameter and 0.8 inches long), making it one of the smallest pentodes ever made. It was designed for high reliability in harsh environments (vibration, shock, temperature extremes).
The CK547DX was used as a high-frequency amplifier, oscillator, or mixer in compact electronics. Key specifications include:
It was prized for its low power consumption, high gain, and reliability in critical applications.
The CK547DX was produced and widely used from the early 1950s through the 1960s. It was common in military avionics, missile guidance systems, portable radios, hearing aids, and early space electronics. Production continued into the 1970s for replacement parts, but it was largely replaced by transistors and integrated circuits by the mid-1960s.
The Raytheon CK547DX is one of the rarest and most sought-after subminiature tubes among collectors. Its tiny size and pentode design made it ideal for ultra-compact, high-reliability circuits. Today, surviving CK547DXs are prized for boutique audio amplifiers and vintage electronics restoration. In the MicroBasement, it stands as a testament to the miniaturization push of the 1950s — when vacuum tubes were shrunk to nearly the size of transistors, just before transistors won the race entirely.