Overview
Eimac was one of the most important American manufacturers of high-power vacuum tubes and radio-frequency power devices. Founded in 1934 as Eitel-McCullough, Inc. in San Bruno, California, the company became a leading supplier of transmitting tubes for amateur radio, broadcasting, military communications, radar systems, industrial equipment, scientific research, and medical applications.
The company name “Eimac” was derived from the surnames of its founders, William “Bill” Eitel and Jack McCullough. Eimac earned a worldwide reputation for innovation in high-power RF technology and became particularly well known among amateur radio operators for products such as the 3-500Z, 4-1000A, 8877, and numerous other transmitting tubes used in high-power amplifiers.
Technical Specifications
| Specification | Details |
|---|---|
| Company Name | Eitel-McCullough, Inc. |
| Trade Name | Eimac |
| Founded | 1934 |
| Founders | William “Bill” Eitel, Jack McCullough |
| Original Headquarters | San Bruno, California, USA |
| Industry | Electronic Components |
| Primary Products | Transmitting Tubes, RF Power Tubes, Klystrons, Microwave Devices |
| Markets Served | Amateur Radio, Broadcasting, Military, Industrial, Medical, Scientific |
| Acquired By | Varian Associates (1965) |
| Successor | Communications & Power Industries (CPI) |
Description
Eimac specialized in the design and manufacture of high-power vacuum tubes and RF power devices. The company’s products were used in radio and television transmitters, radar systems, communications networks, industrial RF heating equipment, particle accelerators, and medical systems.
Among amateur radio operators, Eimac became synonymous with high-power amplifier tubes. Many of the company’s designs remained industry standards for decades and continue to be used by radio amateurs and commercial operators today.
The company was also a pioneer in ceramic-metal tube technology and developed advanced power devices including klystrons, inductive output tubes (IOTs), traveling-wave tubes, and microwave power tubes.
History
Bill Eitel and Jack McCullough were both amateur radio operators and engineers employed by Heintz & Kaufman in San Francisco. Frustrated by the limitations of transmitting tubes available to amateur operators, they developed improved tube designs capable of operating efficiently at lower voltages. In 1934, they left Heintz & Kaufman and founded Eitel-McCullough, Inc. in San Bruno, California.
The company’s first Eimac-branded product was the 150T transmitting triode. Demand from amateur radio operators and commercial users helped establish the company as a growing force in the vacuum tube industry.
During World War II, Eimac became a major supplier of transmitting tubes for military radar and communications systems. Wartime production expanded the company from a small manufacturer into one of the nation’s leading producers of high-power vacuum tubes.
Following the war, Eimac expanded into broadcasting, television, industrial heating, and scientific applications. The company also operated FM radio station KSBR in San Bruno from 1947 to 1959.
In 1959, Eimac moved operations to a newly constructed manufacturing facility in San Carlos, California. The facility became one of the best-known vacuum tube manufacturing plants in the United States.
In 1965, Eitel-McCullough merged with Varian Associates and became the Eimac Division of Varian. The Eimac name continued to be used on products for decades afterward.
In 1989, the Eimac Division received an Engineering Emmy Award for its Klystrode inductive output tube technology used in television broadcasting.
In 1995, Varian’s Electron Device Business was sold and became Communications & Power Industries (CPI). The Eimac product line continues today as part of CPI’s microwave and power products operations.
Historical Addresses
Eitel-McCullough, Inc.
405 San Mateo Avenue
San Bruno, California
Eitel-McCullough, Inc.
301 Industrial Road
San Carlos, California
Timeline
| Year | Event |
|---|---|
| 1934 | Eitel-McCullough, Inc. founded by Bill Eitel and Jack McCullough in San Bruno, California. |
| 1934 | Introduction of the 150T, the first Eimac-branded transmitting tube. |
| 1941–1945 | Major supplier of transmitting tubes for Allied radar and military communications systems during World War II. |
| 1947 | Eimac begins operation of KSBR FM radio station. |
| 1959 | Company moves to a new manufacturing facility in San Carlos, California. |
| 1965 | Acquired by Varian Associates and becomes the Eimac Division. |
| 1989 | Receives Engineering Emmy Award for Klystrode IOT technology. |
| 1995 | Becomes part of Communications & Power Industries (CPI). |
| Present | Eimac products continue to be manufactured for broadcasting, military, scientific, and industrial applications. |
References
- https://www.cpii.com/history/
Official history of Communications & Power Industries and the Eimac product lineage. - https://www.mppinc.com/history/
History of Eitel-McCullough, Eimac, and their integration into CPI. - https://archives.stanford.edu/catalog/m0917
Stanford University archival records documenting Eimac operations and history. - https://oac.cdlib.org/findaid/ark:/13030/c8vt214h/
Archival collection containing historical Eimac corporate records. - https://en.wikipedia.org/wiki/Eimac
Historical overview of Eitel-McCullough and the Eimac brand.