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The name "Hammarlund" is synonymous with a golden age of radio, a time when a well-built communications receiver was a prized possession, connecting amateur radio operators, shortwave listeners, and military personnel across the globe. Hammarlund Manufacturing Company was a cornerstone of this era, and its legacy continues to resonate with collectors, historians, and enthusiasts of vintage electronics. The company's story is one of innovation, quality, and a profound impact on the development of radio technology, particularly in the realm of high-performance receivers.
Founded in 1910 by Swedish-born Oscar Hammarlund in New York City, the Hammarlund Manufacturing Company became one of the most respected names in the history of radio equipment. For over six decades, the company’s name was synonymous with precision, quality, and innovation, producing a range of components and receivers that were highly sought after by amateur radio operators, commercial users, and military and government agencies.
Oscar Hammarlund, an engineer who had previously worked for the Ericsson Company in Stockholm and Western Electric in the United States, was a visionary. His early work included a significant contribution to the development of the Teleautograph, a precursor to the facsimile machine. In 1910, at the age of 50, he established his own company in a loft on Fulton Street in Manhattan to pursue his ideas in the burgeoning field of radio.
The company's initial focus was on high-quality radio components, and it was in this area that Hammarlund first made its mark. Their variable capacitors, in particular, quickly gained a reputation for superior design and precision. A landmark development was the "Midline" variable capacitor, which was introduced in 1919 and soon became an industry standard. The design of this component—two sets of plates, one fixed and one rotating, separated by an air gap—was so fundamental to radio technology that its schematic symbol was adopted as the company's logo.
In the mid-1920s, Hammarlund expanded its business by forming a partnership called Hammarlund-Roberts Co. This new venture specialized in offering kits for AM broadcast radios, using Hammarlund’s own high-quality parts. The kits were popular with hobbyists and experimenters, and the company quickly became a go-to source for builders. When the Great Depression hit in 1931, the kit market waned, and Hammarlund-Roberts Co. was dissolved. This shift prompted the Hammarlund Manufacturing Company to move its focus from components and kits to the production of complete, pre-built radio receivers, setting the stage for its legendary reputation.
Hammarlund's entry into the ready-made radio market was marked by an important innovation: the first commercially produced superheterodyne communications receiver. This was a significant technological leap. The superheterodyne design offered far superior selectivity and sensitivity compared to earlier designs.
The first of these receivers, the "Comet," was a success upon its release in late 1931. An improved version, the "Comet Pro," followed in 1932. This eight-tube marvel was widely adopted for professional listening posts and was used on major exploration expeditions, establishing Hammarlund’s credentials as a producer of high-performance equipment for demanding applications.
In 1935, Hammarlund engineers began work on what they hoped would be the "ultimate" communications receiver. Their goal was to create a receiver that would be a new standard for the industry, with no expense spared in its design and construction. The result, introduced in 1936, was the legendary "Super Pro" series.
The Super Pro was a marvel of engineering. Its build quality was second to none, and it incorporated a number of innovative features that set it apart from its contemporaries. The receiver's precision tuning assembly was virtually sealed, with custom-designed variable condensers and a cam-operated, knife-switch-type band-switch. One of its most celebrated features was its continuously adjustable IF bandwidth, which was achieved through variable-coupled, air-tuned IF transformers. This gave operators unparalleled control over selectivity, allowing them to precisely filter out interference.
The Super Pro series, particularly the SP-200 and SP-600 models, saw extensive use during World War II. The SP-200, an 18-tube, single-conversion superheterodyne receiver, was adopted by the U.S. Signal Corps as the BC-779 and BC-794 and was used at listening posts by agencies like the FBI. After the war, the SP-600 series, which surpassed the SP-200 in performance and used 20 tubes, became a staple for military, commercial, and laboratory applications around the world. These receivers were known for their rock-solid stability and their ability to stay tuned for long periods, which was essential for applications like teletype reception. The SP-600 series was so successful that it remained in production for over two decades, with numerous variations tailored for specific applications.
Here is a list of the main models in the series:
SP-10 (1936): This was the first model to be officially designated as a "Super-Pro" receiver. It was a groundbreaking superheterodyne receiver that set the standard for the entire series.
SP-100 (1937): An improved version of the SP-10, the SP-100 was a direct successor that continued the legacy of the original Super-Pro.
SP-200 (1939): This model was a significant upgrade and is widely considered one of Hammarlund's finest pre-war receivers. It was adopted for extensive military use during World War II, often with military designations like BC-779 and BC-794.
SP-400 (1946): Introduced shortly after World War II, the SP-400 was a continuation of the Super-Pro series, incorporating refinements and improvements based on wartime experience. It was produced in various versions, including the SP-400-X and SP-400-SX.
SP-600 (1951): The SP-600 is arguably the most famous and longest-running model in the Super-Pro series. With over 40 different variations produced from 1951 until the early 1970s, it became a standard for military, commercial, and government communications worldwide. The SP-600 was a highly sophisticated and robust receiver, featuring a wide frequency range and exceptional performance that made it a legend in the world of professional radio.
While the Super Pro series was the flagship professional line, Hammarlund also catered to the amateur radio market with its highly popular "HQ" series of receivers. This line of receivers offered a balance of performance, features, and affordability that made them a favorite among radio enthusiasts.
The HQ series, which included models like the HQ-100, HQ-110, HQ-120, and the post-war HQ-129X, incorporated many of the design principles and features of the Super Pro series in a more compact and accessible package. For example, the HQ-129X, introduced after World War II, was a general-coverage receiver that featured a crystal filter for enhanced selectivity and a robust chassis design. Its tube lineup, which included an RF amplifier and three IF amplifier stages, gave it excellent performance for its class. The separate bandspread dial with calibrated amateur band markings was a particularly appealing feature for hams.
As technology evolved, Hammarlund continued to innovate within the HQ series. Later models, like the HQ-140XA and HQ-150, introduced miniature tubes and improved circuitry for better stability. The HQ-170 and HQ-180 series, in the late 1950s and early 1960s, embraced the growing popularity of single-sideband (SSB) communication with the inclusion of product detectors and crystal-controlled conversion oscillators, offering advanced features that amateur operators demanded.
By the 1960s and early 1970s, the radio industry was undergoing a rapid transformation with the advent of solid-state electronics. While Hammarlund had built a reputation on its tube-based designs, the company struggled to adapt to the new market realities. It attempted to diversify its product line, producing land-mobile radios, Citizens band (CB) radios, and even a "Village Radio" for the United States Agency for International Development (AID) for use in Vietnam. However, these efforts were not enough to sustain the company in the face of intense competition and a changing technological landscape.
For most of its existence, Hammarlund was a family business. Oscar Hammarlund founded the company in 1910 and remained a central figure until his death in 1945. His son, Lloyd Hammarlund, then took over the reins. Under Lloyd's leadership, the company continued to thrive, producing the legendary SP-600 series and the popular HQ line of receivers.
However, as the 1950s drew to a close, the company began to face new challenges. The radio industry was in a period of rapid change, with the shift from vacuum tubes to solid-state transistors starting to gain momentum. The traditional, high-end tube receivers that had been Hammarlund's bread and butter were becoming expensive to produce and less competitive against newer, more compact, and more efficient solid-state designs. This period of transition ultimately led to the first sale of the company.
In the late 1950s, Hammarlund was sold to Telechrome. Telechrome was a company that manufactured telecommunications equipment and was likely interested in Hammarlund's established brand and its manufacturing capabilities. However, this ownership was short-lived.
Within a few years, Telechrome sold Hammarlund to Giannini Scientific Corporation. Giannini Scientific was a diversified aerospace and electronics company, and its acquisition of Hammarlund was likely part of a strategy to expand its portfolio. During this period, the company's focus began to diversify, and it made efforts to enter new markets, such as land-mobile and Citizens band (CB) radio. While some of these products were well-received, they never achieved the same iconic status as the "Super Pro" or "HQ" series receivers. The frequent changes in ownership during this period likely caused instability and disrupted long-term strategic planning.
The final change in ownership occurred in the late 1960s when Giannini Scientific sold Hammarlund to the Electronic Assistance Corporation (EAC). This was the final chapter for the company as an independent entity. EAC was an electronics conglomerate that had a wide range of interests, and the acquisition of Hammarlund was another move to consolidate various electronic businesses under one umbrella.
Under EAC, the Hammarlund brand continued to be used for a few years, but its once-dominant position in the market was fading. The company's classic receiver designs were becoming outdated, and it was unable to make a successful transition to the new solid-state technology. The focus shifted away from the amateur and professional communications receivers that had made the brand famous.
The end came in 1973. The last remaining assets of the Hammarlund Manufacturing Company were sold off. The receiver and equipment division was purchased by Pax Manufacturing Company of New Jersey, and the capacitor and parts division—the original core of the business—was sold to Cardwell Capacitor Corporation. With these sales, the Hammarlund name was phased out. The factory in Mars Hill, North Carolina, which had been the company's main manufacturing facility since 1951, was shut down.