Swan SW-121 User Manual

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.

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.

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
Kc nomial bandwidth, and the upper sideband passes through and is amplified in V7, a 6BA6. The
sideband suppression is rated at 40db, and the filter is made up of four crystals and a centre
tapped inductor.
VFO output is mixed with the upper sideband signals in the 12BE6 mixer V3. The VFO frequency
is higher than the sideband frequency, and since the difference is used, the sideband is inverted
after conversion to 3.8 to 4.0 Mc. A lower sideband signal appears at the grid of V2, the 12BY7
driver. The plates of the two mixers, V2 and V3, are both tuned by the front panel Exciter
Control. The two stages are tuned by a single butterfly capacitor, one side for each stage. A
neutralized sweep tube, V1, a 6DQ5, is the rf amplifier, and the pi-network output is designed for
a 50 ohm load.

RECEIVER