Swan SW-120 User Manual

The Swan SW-120 was the first Swan transceiver produced, and appeared with
a gold coloured face plate. There were at least three different versions of the SW-120, with
revised meters power output, and face plate colour changing from the gold to a grey. The picture
of this fine SW-120 was supplied by NS6C and is a very early model.

SWAN SW-120 TRANCEIVER

TECHNICAL SPECIFICATIONS....

130 Watts PEP from a 6DQ5 PA tube.

TUBE COMPLIMENT

V1- 6DQ5 P.A.
V2- 12BY7 Driver
V3- 12BE6 Trans. Mixer
V4- 12AU6 VFO
V5- 6BA6 Receiver Amplifier
V6- 12BE6 Receiver Mixer
V7- 6BZ6 1st IF
V8- 6BA6 2nd IF
V9- 7360 Balanced Modulator
V10- 6V6GTA AF Output
V11- 12AU7 Microphone Amp
V12- 12AX7 Product Detecter

V13- 6BA6 Carrier Osc.
V14- 0D3 Voltage Regulator
V15- 12AV6 A.F. Osc.

SPECIFICATIONS.

Frequency Range: 14.2 - 14.35 Mhz

High Frequency crystal lattice filter, 3Kc nominal bandwidth. Unwanted sideband down
approximatly 40 db. Carrier suppression approximately 50 db. Receiver selectivity also
determined by crystal filter.
Receiver sensitivity less than 1 microvolt at 50 ohms input impedence for signal-plus-noise / noise
ratio of 6 db.
Transmits automatically on receiving frequency.
Mechanical, electrical, and thermal stability exeptionally high. Oscillators are voltage regulated
and temperature compensated.
Controls include: Main tuning, Volume, Carrier Balance, Mic. Gain, Exiter Tuning, P.A. Tune,
P.A. Load, T-R Switch, Supply On-Off Switch, and Tune Switch.
Microphone Jack (1/4") provides for push-to-talk operation.
Transmits on AM, (single sideband with carrier) with carrier power of approximatly 25 watts.
Audio response essentially flat from 300 to 3000 cycles on both receive and transmit.
Meter reads P.A. cathode current, 300 ma. full scale.
Size: 13 1/4" wide, 5 5/8" high, 11" deep.
Weight: 11 pounds.

POWER SUPPLY

The original SW-120 as advertised in January 1962 recommended the Heathkit HP-10 or HP-20
power supply. This yielded 130 watts PEP, which was later increased to 180 watts and then 240
watts by increasing the high voltage from 650 VDC to 800 VDC. CAUTION: check the mod
sheets before connection of the Heathkit supplies.

TRANSMITTER

When transmitting, audio from a high impedance microphone is amplified in the two triode
sections of V11, a 12AU7. This signal is used to modulate the 5.7726 Mc (changes in later
models) signal generated by the crystal controlled carrier oscillator V13. Modulation and carrier
suppression are taken care of in the 7360 balanced modulator, V9. This gives a rated carrier
suppression of about 50db. The two sidebands are fed into a crystal lattice type filter having a 3