09-26-2013, 09:08 PM
I repurposed an old "Superior Instruments" (not that superior anyhow
) signal generator (100KHz to 180MHz, 6 bands) to become an AM modulator microtransmitter. I removed the generator's old modulation circuit, which modulated the oscillator, which produces both AM and FM. Yuck. 
That old modulation triode (the other section of the osc 12AT7) became a cathode follower to provide unmodulated RF output. I built a new modulator circuit, using a 6CS6 pentagrid tube. It's similar to a 6BE6 except it's sharp cutoff. Which you want for audio. I included an AM detector to produce a feedback signal to the input audio driver amp 6AV6 tube. This to remove some distortion from the modulation.
) signal generator (100KHz to 180MHz, 6 bands) to become an AM modulator microtransmitter. I removed the generator's old modulation circuit, which modulated the oscillator, which produces both AM and FM. Yuck. That old modulation triode (the other section of the osc 12AT7) became a cathode follower to provide unmodulated RF output. I built a new modulator circuit, using a 6CS6 pentagrid tube. It's similar to a 6BE6 except it's sharp cutoff. Which you want for audio. I included an AM detector to produce a feedback signal to the input audio driver amp 6AV6 tube. This to remove some distortion from the modulation.