Name: Hammarlund SP-600
Brand: Hammarlund

1951

Introduced

Frequency	RX: 0.54–54 MHz (6 bands)
Bands	MW, HF, VHF (to 54 MHz)
Power	RECEIVER ONLY. No transmitter. Communications receiver.
Modes	AM, CW, SSB
Weight	39 kg (86 lb) - ~39 kg (86 lbs). BOATANCHOR. Rack-mountable or in cabinet. Built like a battleship.
Connector	binding posts / SO-239
Year	1951

Connectors

antenna	binding posts / SO-239
phones	headphone jack (front panel, 8000Ω)
audio out	600Ω output (professional, NOT 8Ω!)
crystal	crystal frequency preset positions (JX models)
ac in	AC mains (adjustable 110/220V)
power req	AC mains (110/220V adjustable).

THE military/professional communications receiver (US Signal Corps, Coast Guard, FCC monitoring, embassies) boatanchor icon RECEIVER ONLY (no transmitter) 540 kHz to 54 MHz continuous coverage in 6 bands dual conversion above 7.4 MHz (single conversion below) turret-type bandswitch (extremely precise mechanical design, pointer rises and falls across tuning scales!) crystal IF filters (variable selectivity) variable selectivity single crystal filter six crystal-controlled frequency presets (JX models, 'X' suffix = crystal positions) gas-tube regulated (0A2 voltage-regulator tubes) for oscillator stability 600Ω output impedance (professional standard!) + 8000Ω headphone output WARNING: do NOT connect 8Ω speaker directly, 600Ω output! all-tube design with B7G series tubes (easily obtainable) US military designations: R-274/FRR series (Signal Corps), many suffix variants manufactured 1951-1972 (21 years of production!) dozens of variants: SP-600-JX, SP-600-J, SP-600-JLX (100-400 kHz + 1.35-29.7 MHz), etc. very heavy at ~39 kg / 86 lb, the archetypal 'boatanchor' used by US Signal Corps, Coast Guard, FCC monitoring stations, and embassies worldwide; held by the NSA's National Cryptologic Museum VINTAGE. DISCONTINUED B7G tubes; ~38 kg boatanchor produced 1951-1972; many JX/J/JLX variants

Strengths

The professional/military communications receiver. Continuous 540 kHz-54 MHz in 6 bands, dual conversion above 7.4 MHz, crystal IF filters with variable selectivity, and a precise turret bandswitch. Built to military spec and produced for 21 years (1951-1972). B7G tubes remain available.

Weaknesses

Receiver only. A ~38 kg boatanchor needing real bench space. The 600-ohm audio output needs a matching transformer for an 8-ohm speaker. All-tube, with a BFO (no SSB filter) and no digital display.

Verdict

A professional standard. The SP-600 was the communications receiver that militaries and agencies relied on (US Signal Corps, Coast Guard, FCC monitoring, embassies), designated R-274/FRR in US service. The turret bandswitch is a feat of mechanical precision. Built 1951-1972, it is the archetypal professional boatanchor, just remember its 600-ohm audio output.

The Hammarlund SP-600 'Super-Pro 600' is one of the most respected professional communications receivers ever built (a heavy, superbly engineered tube set) descended from the late-1940s Super-Pro line and produced from 1951 to 1972, that became a standard for military, laboratory, and commercial monitoring around the world. It covers 540 kHz to 54 MHz in six bands, with dual conversion on the higher ranges, crystal IF filters, and six crystal-controlled frequency presets for instantly returning to fixed channels, receiving AM, CW, and (with the BFO) single sideband.

Built without regard to cost, the SP-600 is renowned for its sensitivity, its smooth, precise tuning, and its sheer mechanical quality, the kind of receiver that feels like laboratory instrumentation. Many variants served in government and broadcast service for decades. Massive and demanding to restore, it is nonetheless a holy grail for collectors of professional tube receivers, prized for performance that still impresses generations later.

It is a discontinued classic. Compare it with the original Super-Pro and the Hallicrafters SX-28.