Hammarlund

The first Hammarlund plant was a loft operation engaged in radio component manufacturing on Fulton Street in Lower Manhattan, New York City.

Their variable capacitor designs quickly became industry standards, and the component's schematic symbol was adopted as the company's logo.

In addition to manufacturing Super-Pro receivers (Signal Corps model BC-779), Hammarlund variable capacitor production totaled 1 million a month.

[1][3] At the end of World War II, the market was flooded with surplus receivers, which may be a reason many working examples of this model are still found today.

In 1947 the SP-600 Super-Pro receiver, which surpassed the SP-200 in performance, was introduced, covering the frequency range of 540 kHz to 54 MHz with a 0–100 calibrated mechanical band spread.

[2] Even as the company continued to produce communications equipment for the amateur, commercial, and Citizens Band radio markets, it underwent frequent changes of ownership.