A crystal controlled local oscillator

This small module is used to provide the carrier in an SSB transmitter. It can be used between approximately 8 and 12 MHz (and beyond).

There are two stages (an oscillator and a buffer stage) each equipped with standard transistors like the 2N2222 or other types using the E-B-C basic pinout. It uses 1 crystal. Sideband switching and precise tuning is achieved by switching either a coil (Lx) or a variable capacitor (Cx, 5..90pF) in series with the respective crystal.

Local oscillator (crystal controlled)
Local oscillator (crystal controlled)

The PCB for this unit:

Local oscillator PCB

Lx is a tapped coil. A TOKO style 5-pin coil former is used. The asterisk (*) marks the position of the coil’s beginning. From here to the next pin (clockwise view from top) is 16 turns, then 8, 4 and 2. A flexible hookup wire is used to connect the respective pin to the “USB” pin for the sideband selector switch.

C1 and C2 are couplers for the respective output (usually either the TX DSB generator or the RX demodulator). Leads to the switch visible on the left side should not exceed 5 centimeters.