Hammarlund Mfg. Co., New York / Mars Hill NC
SP - 600 - JX / Super Pro SP-600
überarbeitet am 14.11.2010
The Super Pro / SP-600 is the latest and last model of Hammarlund's Super Pro series, it has been produced from 1951 until 1961 in numerous variants for the military and civil market.
The receiver is a veritable "Boatanchor", the version with the desktop cabinet is 55 x 32 x 44 cm wide and has a weight of 39,4 kg and the rack version 48 x 26,6 x 44 cm wide has a weight of not less then 30 kg. The receiver can be powered from different voltages from 90 - 270 V and 50-60 Hz, some J versions even with 25 - 60 Hz, power consumption is around 130 Watts.
In the centre of the frontpanel, You find the two dial windows. A mechnically moved pointer (looks like a sharpened pencil) points to the active dial on the left main tuning dial, it is moved by the band selector knob just below. The right dial is the fine tuning dial of which only the active part is visible through a small aperture. Both dials are coupled mechanically, the set is tuned from the main tuning knob below the right bandspread and logging dial. The dial accuracy of the main dial is around 25 kHz in the 49 m band and on worse on higher frequencies, e.g. around 50 - 100 kHz in the 19 m band. The tuning lock knob locks the tuning mechanism mechanically.
The receiver's main switch is mechanically coupled to the RF gain control,
this will let You manually adjust the high frequency amplification, at least if
thw AVC switch in the right lower corner is in the MAN(ual) position. The volume
control is located in between the band selector and the main tuning knob.
In the left lower corner of the front panel, You find the switches for TRANSMIT / RECeive
operation, the headphones jack and the noise limiter, the receiver has no internal speaker.
The R.F. signal coming from the antenna is amplified in two stages (V1 and V2, 6BA6, 6BA6),
in the first mixer (V5: 6BE6), it will be mixed with the signal from the crystal oscillator
(V3: 6AC7) for fixed frequency operation or from the VFO signal (V4: 6C4) to generate
the intermediate frequency of 455 kHz in bands 1 - 3, which will be amplified (V7: 6BA6).
In bands 4 and 5m the resulting first intermediate frequency 3955 kHz will me mixed with a 3,5 MHz
oscillator signal (V8: 6C4) in the second mixer (V6: 6BE6) to end with the same intermediate frequency
of 455 kHz.
The typeplate is usually found on the cover of the r.f. unit: J- will say that all components meet the JAN (Joint Army Navy) Standard requirements, a X that the receiver is equipped with an oscillator for crystal controlled fixed frequency operation, and a L, that the set covers not the mediumwave band but the longwaves, used in the United States for aeronautical beacons (NDB). Find further informations about the different SP-600 variants based on the excellent survey made by Les Locklear > > > here < < <.
© Martin Bösch 28.4.2008 / transl. 15.11.2010