R-274/SP600 Receiver

R-274/SP600 Receiver

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General Description

The R-274 is the U.S. Navy version of the Hammarlund SP600.

The SP600 was of post war design and was produced during the period 1951 - 1972.

The receiver covers the frequency range 0.54 - 54 MHz in 6 bands. It was designed to receive AM and CW transmissions. The set was used widely by commercial services and had a split winding 600 ohm output transformer for remote external speakers and driving teleprinter loops.

These sets sold for between US $985 and $1140 when new.

Technical Data

SP600 label The set uses single and double conversion techniques, depending on the frequency range. The IF on the lower 4 ranges is 455kc, with double conversion on the top 2 bands using 3.955 mc as the additional IF frequency. It is fitted with a crystal filter. A selectivity switch gives a choice of 6 passbands.

There is provision for crystal control on 6 channels as well as the normal local oscillator. If the crystals have been ordered through Hammarlund, the frequency stamped on them is the receiver operating frequency, not the resonant frequency of the crystal.

In total there are 20 valves in the receiver. The coils are mounted on ceramic slabs and are mounted in a turret.

The set is capable of excellent performance, but does not resolve sideband in the original state.

The set is quite prized by collectors - but they need muscles, plenty of room and a strong table. The set weighs around 40kg.

Sensitivity is 2-3 microvolts across the entire frequency range for 10db s/n at 20 milliwatts output.

The display receiver has been used on a radio-teletype circuit for receiving transmissions from the United States and the Philipines, probably associated with a press service.

Illustrations of the set

Views inside the receiver SP600 bottom SP600 top

More views SP600 dial SP600 back

Crystals for pre-set frequencies SP600 xtals SP600 channels

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© Ian O'Toole, 2009. Page created: 16/04/04 Last updated: 11/12/2009