Note
QST, Feb 1963, p. 99.
QST, Jan 1964, p. 137.
The Swan SW-240 is a three-band, single-sideband (SSB) suppressed-carrier vacuum tube transceiver manufactured by Swan Electronics Corporation. Designed for fixed, portable, or mobile operation, it covers the 20-, 40-, and 75-meter bands. It was lower sideband only on 75 and 40, upper sideband on 20. An optional accessory was necessary to use the other sideband. Power input was 240 watts SSB, 200 watts CW, and 60 watts carrier power on AM with a 6DQ5 final.
The SW-240 utilizes single conversion on both transmit and receive, centered around a 5174.5 kHz reference intermediate frequency (IF).
Specifications
– Operating Bands & Frequency Ranges:
20 Meters: 13,990 to 14,380 kHz (Upper Sideband standard).
40 Meters: 6,900 to 7,340 kHz (Lower Sideband standard).
75 Meters: 3,640 to 4,030 kHz (Lower Sideband standard).
Note: Operation on the opposite sideband is available as an optional factory addition via an added crystal oscillator.
– Power Input Ratings:
SSB: 180 Watts PEP input with a 600V DC high-voltage supply, or up to 240 watts PEP input using an 800V DC high-voltage supply.
CW: 200 Watts DC input.
AM (SSB with Carrier): Approximately 60 Watts input.
– Carrier Suppression: Approximately 50 dB.
– Unwanted Sideband Suppression: Approximately 40 dB.
– Receiver Sensitivity: Less than 1 microvolt at 50 ohms input impedance for a 10 dB signal-plus-noise to noise ratio.
– Audio Response: Essentially flat from 300 to 3000 Hz on both transmit and receive.
– Audio Output: 3 Watts into a 3.2-ohm speaker load.
– Output Circuitry: A variable Pi-network output circuit matches resistive antenna input impedances between 20 and 300 ohms.
Tube Lineup (15 total)
– 6DQ5 (or 8236) Final Power Amplifier:
– 12BY7A Driver:
– 6BE6 Transmitter Mixer:
– 6AU6 VFO:
– 6U8A Carrier Oscillator / Isolation Amp:
– 7360 Balanced Modulator:
– 12AU7 Microphone Amplifier:
– 6CB6 1st IF Amplifier:
– 6BA6 2nd IF Amplifier:
– 6BA6 Receiver RF Amplifier:
– 12BE6 Receiver Mixer:
– 12AX7 Product Detector & 1st AF Amp:
– 6AL5 AGC Rectifier:
– 6V6GTA AF Output Amplifier:
– 0D3 Voltage Regulator:
Power Requirement: The transceiver requires an external power supply connected via a rear-panel Jones connector. It relies on external supplies such as the Swan SW-117AC (for fixed AC operation with built-in speaker) or the SW-12DC (for 12V mobile operation). Power requirements include 12.6V AC/DC filament voltage at 3.45 amps, -100V DC bias, +275V DC medium voltage, and +600V to +800V DC high voltage for the PA plate.
References
Review. 73, Apr 1963, p. 90.
Adding ALC. 73, Nov 1965, p. 40.
