The Hammarlund Super Pro was an American made radio communications receiver.
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In March 1936, the Hammarlund Manufacturing Company initiated the first of the famous “Super-Pro” line, the SP-10 receiver, followed in January 1937 by the SP-100. Their efforts to improve the design resulted in October 1939 with the SP-200 series, an 18-tube, single conversion superhet receiver.[1] While designed as a communications receiver, Hammarlund also promoted a home version in a console cabinet during the mid-thirties [2] The SP-200 series Super-Pro receivers were manufactured through 1945, with many thousand delivered to the military during World War II and saw wide use by the U.S. Signal Corps. The Military designations for the receiver were BC-779-A/B (the most common), BC-794-B, BC-1004-C as well as R-129/U and R-270/FFR. During World War II, government agencies like the FBI used the 200 Series Super-Pro at their listening posts.[3] Many were used at ground stations in England to communicate with the Royal Air Force and U.S. Air Force armadas that flew bombing missions over Germany.[4] According to a November 1940 QST Magazine ad, "The fact that 'Super-Pro' receivers are used extensively by the U.S. Signal Corps and many other governmental departments, speaks for itself." At the end of the war, the market was flooded with surplus Super-Pro receivers at bargain prices, which may be a reason many working examples of this model are still found today. From 1946 to 1948, Hammarlund produced the SP-400 Super Pro for the amateur radio market. In 1947 the SP-600 Super-Pro receiver, which surpassed the SP-200 in performance, was introduced. The SP-600 series were widely used throughout the world for military, laboratory and commercial application.[5]
Various models of the SP-200 series cover 0.1 - 40 MHz in 5 bands. The radio and cabinet weigh 73 pounds (33 kg) while the separate power supply adds another 57 to 61 pounds. The Super-Pro was first offered in two basic models, one with, and one without, a crystal filter.[6] All the models are 18-tube (16 in the receiver, 2 in the separate power supply), single conversion superhets with 2 RF stages and 3 IF stages operating at 465 kHz. In addition to a 5 position single-crystal filter with variable phasing, the IF selectivity is continuously variable between 3 and 16 kHz. The radios are equipped with full bandspread on all except the 0.1 to 0.4 MHz bands, variable BFO, diode noise limiter, and 14 watts of audio output power. Claimed sensitivity is 1.0 to 1.7 microvolts on the LF and HF ranges. The main dial calibration is 1/2 of 1 percent of the highest frequency on each band. Total power consumption is about 180 watts.[7] Initially, two versions were manufactured. One tuned from the low end of the broadcast band to 20 MHz, and the other started at 1250 kHz and went up to 40 MHz.[8]
The three basic models (there were additional variants and modifications) were:
The SP-400 Super Pros were very similar to the SP-200's with the differences being mainly cosmetic. They were only made from 1946 to 1948 and had outboard power supplies like the earlier Super Pros. There were two of them, the SP-400-X which tuned from .54 to 30 MHz, and the SP-400-SX which tuned from 1.25 -40 MHz.[10]
The SP-600 Super Pro covered the frequency range of 540 kHz to 54 MHz with a 0-100 calibrated mechanical band spread. The receiver had provisions for optional crystal control of six selected frequencies. A number of variants were produced.[11]