Output-stage Construction

Power Amp Construction Diagram


With the oscillator working, you're read to move on to the output stage. It includes only six parts, so construction won't take long.

  1. Solder the "cold" end of the transformer secondary to ground.
  2. Mount the 39ohm resistor near the secondary by soldering one end of the resistor to ground.
  3. Solder the free end of L2, the transformer secondary, to the top end of the 39ohm resistor.
  4. Mount the output transistor* by soldering the emitter to ground and the base to the top of the 30ohm resistor. Position the collector so that it can be connected to the output filter.
  5. Solder the zener diode between the collector of the output transistor and ground. The banded end should go to the transistor.
  6. Solder one end of the molded RF choke (black) to the collector of the output transistor.
  7. Solder a 0.1 disk capacitor to the collector of the transistor. This capacitor couples RF to the output filter, so position it accordingly.
  8. Solder a 0.1 disk capacitor from the 12-volt end of the RF choke to ground.
  9. Now connect a jumper from between terminal strip lugs 2 and 5, connecting the 220ohm resistor and the RF choke.

Output Filter

  1. Solder one 820pF capacitor between the free end of the output coupling capacitor and ground.
  2. Solder another 820pF capacitor to ground about a half inch from the first one. Leave the unsoldered end sticking up free.
  3. Solder L3 (21t #22 on T-50-2) between the ungrounded ends of the two 820 capacitors.
  4. Install the output connector of your choosing.

* Output transistor, Q2 = 2N3053, 2N3866, BFQ163 or equivalent.
  1. Double check your wiring.
  2. Have another person check your wiring too!
  3. Make sure the jumper (step 9) is in the right place.
  4. Connect a load to the output.
  5. Apply 12 volts, as shown. You should get a watt or more of blazing RF power output.

Now on to Raw Power!