First-stage Construction

Oscillator Construction Diagram

The first stage of construction of this project is, literally, construction of the transmitters first stage--the oscillator.

This oscillator uses a 2N2222. Frequency is determined by the crystal; the output is tuned by a trimmer capacitor in parallel with the primary of L1/L2 transformer.

This is a reliable, easy to build circuit. I've constructed dozens of 'em, and they always work.

First, mound (solder) a terminal strip near the front left side of your board. To mount the strip, first places a small puddle of solder on the board. Then place the (cleaned and tinned) foot of the terminal strip on the puddle and heat the foot. The solder will soon melt, securely soldering the terminal strip in place.

Prepare the PC Board

Then begin oscillator parts installation. Here's the recommended ugly-construction sequence:

Solder Terminal Strip foot to board.
Solder terminal strip foot to board.
  1. Mount the 4.7K resistor at one end of the board.
  2. Solder the 100pf (white) capacitor and the 220 ohm resistor in parallel.
  3. Solder one end of the 200pf/220ohm combo to the board, positioning it as shown (the transistor emitter will be solder to the other end of this pair).
  4. Solder the base of the 2N2222 to the ungrounded end of the 4.7K resistor, and the emitter to the junction of the 220 ohm resistor and the 100 pF capacitor.
200pF/220ohm combo
  1. Solder the 220pF disk capacitor from the emitter to the base of the 2N2222.
  2. Solder one end of a 10K resistor to the base of the 2N2222. Position the free end as shown.
  3. Install a 0.1 (104) disk capacitor between the free end of the resistor and ground.
  4. Connect one end of a 220ohm resistor to the junction of the 10K resistor and the 0.1 disk cap.
  5. Connect the other end of the 220ohm resistor to an ungrounded terminal on the terminal strip.

Now install the L1/L2 transformer and the trimmer cap, as follows:

  1. Connect one end of the trimmer to the collector of the 2N2222. Solder the other end of the trimmer to ground.
  2. Connect the "cold" end of the primary (magnet wire) winding to the junction of the 220ohm resistor, 10K resistor and 0.1 capacitor.
  3. Connect the other end of the primary winding to the collector/trimmer junction.
  4. Solder the "cold" end of the 5-turn secondary to ground.

Almost Done!

  1. Mount the crystal. One lead goes to ground; the other is soldered to the ungrounded end of the 4.7K resistor.

Testing the oscillator: Apply 12 volts to the terminal strip end of the 220 resistor, and adjust the trimmer while listening on the receiver. When you have the oscillator running go on to the next steps.

Now on to Raw Power!