QST, Jun 1965, p. 1.
QST, Sep 1966, inside front cover.
The SR-500 nomenclature was originally assigned to Hallicrafters complete station-in-a-rack console, released in 1955, and it's reuse with the Tornado could create some small confusion.
The 500 watt SR-500 is essentially and upgraded version of the 150 watt SR-160, in which a pair of 8236 tubes have replaced the 12DQ6s. Note that the 8236 is not a common tube type.
Comparison of the SR-500 and SR-160 reveals only minor circuit differences, but the plate voltage of the SR-500 (800 volts) versus the the SR-160 (575 volts) explains where all the extra power comes from.
The specifications and features of the two units are broadly similar.
Specifications
– Frequency Coverage: Three-band capability with full coverage for 80, 40, and 20 meter amateur bands:
80M Band: 3500 kHz – 4000 kHz
40M Band: 6900 kHz – 7400 kHz
20M Band: 13900 kHz – 14400 kHz
– Stability: Within 300 Hz after warmup.
– Single Sideband: LSB on 80M and 40M bands; USB on 20M band.
– Push-to-talk control (VOX optional accessory).
– CW: Manual.
– Output Impedance: Fixed, 50-ohm pi-network.
– Power Input:
SSB: 500 watts PEP MAX.
CW: 300 watts MAX.
– Carrier and Unwanted Sideband Suppression: 50 DB.
– Distortion Products: 30 DB.
– Audio Response: 600 Hz to 2800 Hz (3 DB).
– Microphone Input: High impedance.
– Sensitivity: 1 microvolt for a 20-DB signal-to-noise ratio.
– Audio Output: 2 watts.
– Output Impedance: 3.2 ohms.
– Overall Gain: 1 microvolt for 1/2-watt output.
– Antenna Input: 50 ohms.
– IF: Single conversion, 5200 kHz with crystal-lattice filter.
– Dial Calibration: 5 kHz increments.
– VFO: 500-KHz tunable range.
– Calibration Accuracy: Less than 2 kHz between 100-kHz points after indexing. (Note: Built-in 100-kHz crystal calibrator circuit requires a 100-kHz crystal and 12AU6 tube to operate).
Tube Lineup (17 total)
– 12AW6 Receiver RF Amplifier
– 12BE6 Receiver Mixer
– 12BZ6 First IF Amplifier
– 6EA8 Receiver Second IF Amplifier and Meter Amplifier
– 12AX7A/ECC83 Product Detector and First Audio Amplifier
– 6AQ5A Receiver Audio Output
– 12AU6 100-KHz Calibrator Oscillator (Not supplied with unit)<br>
– 12AT7 Carrier Oscillator/BFO and Third Microphone Amplifier
– 12AT7 First and Second Microphone Amplifier
– 6AM8A AVC/AALC Amplifier-Detector
– 12BE6 Heterodyne Oscillator and Mixer (40M)
– 0A2 Voltage Regulator
– 12BE6 Transmitter Mixer
– 12BY7A Transmitter Driver
– 8236 Transmitter Power Amplifier
– 8236 Transmitter Power Amplifier
– 6EA8 VFO and Cathode Follower
Power Requirements
117 VAC Power Supply (Model PS-500-AC)
Transmit:700 watts max
Receive:140 watts
12 VDC Power Supply (Model PS-500-DC)
Transmit:16 to 40 amperes max
Receive:10 amperes
References
Brief description. Electronics World, Jul 1965, p. 94.
