I ended up making a couple of modifications to the KG-650 to improve the output. The first was to add a 2 Megohm multi-turn trim potentiometer at the output of the oscillator to reduce the signal level feeding the mixer stage. I adjusted this potentiometer until the output waveform looked much better as you can see below.
If you refer back to the circuit diagram from an earlier post, I clipped the connection between C-8 and pin 6 of V-2. The loose end of C-8 was then connected to the center pin of the potentiometer, one end of the pot was connected to ground and the other end to pin 6 of V-2.
Next I made one more modification to improve the modulation level, The original modulation looked like this.
As you can see it is way over-modulated. By changing R-5 from 33K to 1 Megohm the resulting modulation looks like this.
Not exactly ideal, but certainly less modulated than before. This worked very well when I attached it to the radio.
So that’s it for the KG-650, should be a useful addition to the lab.