E-614, All Wave Receiver SX-42; developed and produced by Hallicrafters Co., Chicago IL.
Hallicrafters launched the SX-42 in 1947. The large double superheterodyne set was the top model of the first receiver generation developed by Hallicrafters after World War II; then it had the most complete frequency coverage for that time. The prototype of the SX-42 was originally designed as 5 - band receiver with a frequency coverage up to 55 MHz. When the American FCC decided not to use the 6 m band but the 3 m band from 88 - 108 MHz as FM broadcasting band, the SX-42 had to be extended by another frequency range to cover the spectrum up to 110 MHz to include the FM broadcasting band.
The SX - 42 comes in an imposing dark gray metal cabinet. Like with other Hallicrafters receivers from the same era, the hinged cover can be opened to access the inside or replace the tubes.
An external 600 ohms speaker must be connected to the high - impedance speaker terminal screws, the original Hallicrafters speaker had the designation R-42.
A round greenish backlit frequency dial, from which only the upper semicircle is visible, dominates the left part of the front panel. The round dial is rotated by the main tuning knob, it has markings for the radio and amateur radio bands in the six frequency ranges and in addition a log scale. The main tuning knob also comes with a 100-division logging dial, which is used to retune a station later.
The inner part of the main tuning knob activates the band spread, unfortunately it is not coupled with the main tuning mechanism. The band spread dial comes with calibration marks for the amateur radio bands and also with a 0-100 division. A knob in the center of the main tuning knob locks the tuning mechanism.
The six frequency ranges are selected with a heavy metal switch on the left of the main dial. Unfortunately, the frequency band labels are only on the outside edge of this controls, it takes some experience or good eyes to read the labels.
The volume control which is combined with the power switch is located at the right of the tuning knob, above the headphone jack, there are three switches which activate the AVC, the noise limiter and switch the set from standby to receive mode.
To the right, there are six controls in two rows.
In the bottom row, the left switch selects on of the 3 IF coil filters three crystal filters, which are especially useful for CW reception. With the Crystal Phasing control, located above it, the pass band can be shifted to phase out an unwanted signal. The tone control at the right of the bandwidth switch has an additional HiFi position, in this position, the receiver gives great audio performance for FM reception, while in the high - mid - low positions, the frequency response is limited for shortwave reception. Above the tone control, the mode switch for FM, AM and CW is located, in the last position the BFO is activated, the BFO note can be adjusted with the CW Pitch control next to it.
In the bottom right, you find the sensitivity control, by the means of which, the high-frequency / IF gain can be controlled manually, especially in the case of overloading. The greenish backlit S-meter has a similar round shape, like the main frequency dial. As a concession to the less technically minded listener, on the SX-42, small red dots mark the normal control position for AM reception and green dots for FM reception.
The radio frequency signal coming from the antenna first has to pass two RF amplifier stages (6AG5, 6AG5) and is converted to the IF of 455 kHz (in AM mode and to the usual 10.7 MHz in FM mode in the first mixer (7F8). After passing the AM coil filters resp. the crystal filters and three IF amplifier stages, in AM mode, the signal is demodulated (7H7). This tube acts also noise limiter. For CW and SSB reception, the subcarrier generated by the beat frequency oscillator (7A4) is added.
After an audio preamplifier stage (6SL7), the audio is fed to the push - pull output stage (two 6V6) which drives the high - impedance loudspeaker connectors.
V1 (6AG5, 1st RF preamplifier); V2 (6AG5, 2nd RF preamplifier); V3 (7F8, mixer, oscillator); V4 (6SK7, 1st IF amplifier); V5 (6SC7, 2nd IF amplifier); V6 (7H7, 3rd IF amplifier); V7 (7H7, AM detector, FM limiter); V8 (6H6, FM discriminator); V9 (6SL7, AF preamp); V10, V11, (two 6V6 in push-pull configuration, AF output stage); V12 (7A4, BFO & FM meter amplifier); V13 (6H6, noise limiter).
Gl (5U4, mains rectifier), stabilizer VR-150.
Information about the purpose of the E-614 / Hallicrafters SX-42 is missing; as the set covers the military VHF range, it has likely been used for military traffic monitoring. The SX-62 as the successor to the SX-42 comes with with a horizontal dial and the same frequency coverage and had the military designation E-605 resp. E-644.