QLF Filter Assembly Procedure

Schematic Previous Page

Part 4 - Assemble the Rig Keying Circuit

So now it is time to bless the world with your new found keying ability. To do this, we gotta hook it to your rig. Most modern rigs require a circuit that drives the key center pin to ground. Little current is normally required, but I have put in a heavy duty higher voltage transistor to be on the safe side. You should be able to drive a relay with no problem. If you do this, dont forget the shunt diode to kill inductive induced spikes. Once again, a .01mfd cap is included to help kill RFI emissions.
  1. Install Q2 2N2222
  2. Install R12 33 ohm connect from Q2-emitter to GND
  3. Install R13 4.7K connect from Q2-base to +5V
  4. Install R14 820 ohms connect from Q2-collector to +5V
  5. Install C4 (.01) between Q2-base and GND
  6. Install D1. Connect - end (without band) to Q2-base
  7. Connect + (band end) of D1 to 87c750-22
  8. Install Q3 2N3019
  9. Install D2. Connect - end (without band) to Q2-collector
  10. Connect + (band end) of D2 to Q3-base
  11. Install R15 100 ohm 1/2 watt. Connect from Q3-emitter to GND.
  12. Install D3 with the + end (band) to Q3 - collector and the other end to GND
  13. Install C6 .01 in parallel with D3.
  14. Temporarily install an extra 220 ohm resistor and LED between +5V and the Collector of Q3 to provide a test indicator.
  15. Power up the circuit again and check that the LED lights when code is being sent.
  16. Note: You must remove the test LED and resistor before attaching to your rig.