E-613, All Wave Receiver SX-25 „Super Defiant“; developed and produced by Hallicrafters Co., Chicago IL.
Hallicrafters presented their all-wave receiver SX-25 in 1940, the single conversion set covers medium- and shortwaves in three ranges.
The all-wave receiver SX-25 comes with an anthracite gray metal cabinet, with its size of 49.5 x 24 x 28 cm and the weight of 21 kg, it is quite bulky. Like in other Hallicrafters radios from the forties, the hinged lid of the cabinet can be opened to change the tubes.
On the front panel, the round frequency dial is located on the left; on the round dial, the frequency is indicated by a vertical line. The window of the band spread dial is located on the right; when the main tuning is set to the corresponding mark, in the spread amateur radio bands, the frequencies can be read directly from the band spread dial.
Two tuning knobs below the bandspread dial act as main tuning and band spread tuning control, in the right upper corner, the analog signal strength meter is located.
In the lower row of control, you find from the left the RF Gain control, the band range switch below the main dial, and on the right the control to select the various IF filters and the crystal filter. The crystal filter control is located between the tone and the noise limiter switch.
Further to the right, you find the volume control which is combined with the power switch followed by the BFO control and the switch for single sideband and CW reception.
The SEND-REC. switch must be set to the REC position (Reception) for normal operation; when operating with a transmitter, the receiver input can be connected to ground during transmission and so the input stage is protected.
The single conversion superhet has two HF preamplifier stages (6SK7 each), the 6K8 acts as oscillator and mixer stage, these are followed by two IF amplifier stages (two 6SK7s), in a 6SQ7 the signal is demodulated, the tube also acts as a AF preamplifier, in the push-pull final amplifier two 6F6s are used. A 6SQ7 acts as phase inverter in the crystal filter, a double diode 6H6 in the noise limiter and a 6J5 in the BFO.
V1 (6SK7, 1st RF preamplifier); V2 (6SK7, 2nd RF preamplifier); V3 (6K8, mixer, oscillator); V4 (6SK7, 1st IF amplifier); V5 (6SK7 , 2nd IF amplifier); V6 (6SQ7, detector, AVC, AF preamplifier); V7 (6SQ7, phase inverter); V8 (6H6, noise limiter); V9 (6J5, BFO); V10 and V11 (two 6F6, push-pull AF final amplifier).
Gl (80, power rectifier).
Information about the purpose of use of the E-613 / Hallicrafters SX-25 in the Swiss Army is missing.