Hammarlund Comet Pro
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The Hammarlund Manufacturing Company was founded by Oscar Hammarlund in New York City in 1910. The first Hammarlund plant manufactured radio components and was located on Fulton Street in lower Manhattan.. Their variable capacitor designs quickly became industry standards, and the company adopted the capacitorís schematic symbol as its logo. Hammarlund formed a partnership called Hammarlund-Roberts Co. in the mid 1920íspecifically to offer kits for AM Broadcast radios using Hammarlund parts.
Hammarlund-Roberts went out of business in 1931 and the Hammarlund Mfg. Co., Inc. introduced of the "Comet Pro", the first commercial shortwave superheterodyne receiver. Within five years, thousands of these receivers were in use at commercial radiotelegraph and radiotelephone stations, aboard ships and by amateur radio operators the world over.
After the Comet-Pro came an improved receiver, called the Super-Pro (the SP-200 series in 1936. Hammarlund expanded with the onset of World War II, with more than 2000 people employed at 14 different plants. It has been estimated that almost 90% of American wartime military electronic equipment employed Hammarlund capacitors. At the end of World War II, surplus Super-Pro receivers at bargain prices were readily available, which may be a reason why so many of these are still survive today.
In 1947, the SP-600 Super-Pro receiver, which surpassed the SP-200 in performance, was introduced. It covered 540 kHz to 54 mHz with a 0-100 calibrated mechanical band spreadand had provisions for optional crystal control of six selected frequencies. Also produced, was a VLF version, which tuned from 10 kHz to 540 kHz. The SP-600 receiver series was popular throughout the world for military, laboratory and commercial uses.
While Hammarlund was most famous for its amateur/short-wave receiver lines such as the Super Pro series and the HQ series (which includes the HQ-100, 110, 120, 129, 145, 150, 160, 170, 180, 200 and 215) it also produced a number of amateur transmitters. In 1960 the HX-500, a 100 watt, table-top, single-sideband transmitter was introduced.This rig also had FM and FSK transmission capability, along with the later HX-50. The HXL-1 was a compact linear amplifier introduced in 1964.
The company changed ownership often. In the late 1950s Hammarlund was sold to Telechrome. Then Telechrome sold out to Giannini Scientific. In the late 60ís the company was sold to the Electronic Assistance Corporation (EAC). The product line was either sold off in parts or phased out. The Cardwell Condenser Corporation purchased all remaining components, and in the early 1970s the Hammarlund factory closed. At the time of its demise, Hammarlund was among the very oldest producers of radio equipment in the United States.
More information on Hammarlund:
Wikipedia reference on Hammarlund
Ham Radio Museum - Hammarlund