Note
QST, May 1961, p. 1.
Allied Radio catalog 1962 (copyright 1961), p. 273.
Allied Radio catalog 1963 (copyright 1962), p. 280.
Allied Radio catalog 1964 (copyright 1963), p. 218.
The Hallicrafters Model SX-115 is an amateur radio communications receiver delivered in 1961. Designed as a high-performance, heterodyne-type triple-conversion receiver, it offers linear tuning, precise readout capability, and stable reception across the major amateur HF bands.
Features
Selectable Sidebands: Upper or lower sideband selection is accomplished during the third conversion stage by switching the crystal-controlled conversion oscillator frequency between 955 KC and 1055 KC.
T-Notch Filter: Provides adjustable nulling within the 50.75-KC passband to eliminate heterodyne interference.
Dual-Loop Amplified AVC: Features fast-attack and slow-release characteristics; AVC action improves effective front-end selectivity.
Noise Limiting: Incorporates an IF-type noise limiter for SSB/CW modes and an automatic series-threshold noise limiter for AM reception.
Frequency Coverage: Covers the 80, 40, 20, 15, and 10-meter amateur bands (with the 10-meter band split into four 500-KC segments covering 28.0 to 30.0 MC), plus a non-calibrated segment for WWV at 9.6 MC to 10.1 MC.
Modes of Reception: AM, CW, and Single Sideband (SSB).
Specifications
Sensitivity: Less than 0.5 microvolts for SSB/CW; less than 1.0 microvolt for AM (for a 10 dB signal-to-noise ratio).
Intermediate Frequencies (IF): Triple-conversion arrangement utilizing 6.505 MC to 6.005 MC (variable IF), 1005 KC (second IF), and 50.75 KC (third IF).
Selectivity: Variable in five distinct steps providing 0.5, 1, 2, 3, and 5 KC bandwidths at 6 dB down.
Calibration Accuracy & Readout: Features a gear-driven tuning mechanism, 1-KC dial calibration marks across all bands, and better than 1000-cycle accuracy between 100-KC calibration points.
Tube Lineup
The receiver uses 18 vacuum tubes (including a voltage regulator) along with 5 silicon diodes:
– 6DC6 RF Amplifier.
– 6BA7 First Mixer,
– 12AT7 Crystal Oscillator for the first conversion.
– 6DC6 First IF stage (6.0 MC to 6.5 MC).
– 6CB6 VFO
– 6BA7 Second Mixer, f
– 6DC6 Second IF Amplifier at 1005 KC.
– 6BA6 Third Mixer
– 12AT7 SSB Switching Oscillator (955 KC / 1055 KC).
– 6DC6 Third IF Amplifier operating at 50.75 KC.
– 6BY6 Product Detector
– 6BJ7 AM detection, second AVC rectifier, automatic threshold noise limiting.
– 12AX7 BFO and First Audio Amplifier.
– 6AQ5 Audio Output stage
– 6AU6 100-KC Crystal Calibrator,
– 6AU6 S-Meter Amplifier and First Loop AVC Amplifier.
– 0A2 Voltage Regulator
Power Requiements: 105–125 VAC, 50/60 Hz, 85 watts.
References
Review: QST, Mar 1962, p. 54.
Review: CQ, Mar 1964, p. 48.
