The device is designed as follows:
- 5.0688 MHz crystal oscillator (74HC86)
- frequency modulation by a brutish rectifier diode (on the PCB's lower side)
- active frequency doubler (74HC86)
- 10.140MHz crystal filter to the final
- 74HCT240 final, run at 5V
- low pass
- keyer: PICAXE 08M
The keyer is programmed to key the final by a PTT signal and modulate the oscillator using pseudo-analogue generated by PWM. In this way a variety of signals can produced. This TX was up to now used with QRSS, DFCW and S/MT-Hell, see earlier post showing PA9QV's snapshot.
Future plan: go QRO-ish by replacing the second 7805 (next to the 74HCT240) with a 7808 and adding a PA (IRF510).