VXO/Keying/Mixer Schematic

D1 in the keying circuit isolates this circuit from any others that may be keyed along with this one, for example, an RIT circuit at the VFO in the receiver.

L5 in the VXO can be changed in value to set the frequencies where you want the pull to go. Values from 47uH to 1mH can be used. Other authors have suggested that molded chokes provide the best performance.

But if a selection of molded chokes are not available, use a T50-2 or T50-6 toroid and wind some up. The T50-2 will give higher inductance values than the T50-6.

The VXO crystal is the same one used in the first crystal filter of the receiver. Or if a commercial filter is used, the same frequency as the filter.

C38 in the VXO is not critical in value. In fact, a capacitor that has the ability to go very low in capacitance may be more desirable than a high value one. Experimentation with L5 and C38 will get you exactly what you want.

All the RF amplifiers are the one used in the Progressive Communications Receiver Post-mixer amplifier. It is very stable and everyone I have built worked first time every time. Other transistors will work just as well in this circuit, including the 2N3866 and similar types.

The filter after the mixer is a bandpass type. Any receiver type bandpass filter will work here that has 50 ohm terminations.

The mixer type is not critical. An SBL-1, SBL-3, TUF-1, or any others, including a homebrewed one will work fine.

If a dual-gate MOSFET is not available for connecting to the VFO, just use an FET buffer, or any circuit that gives a high impedance input to the tap on the VFO circuit and/or amplifier. Since a 2N5109 amplifier follows the circuit, there will be plenty of gain for anything used.