Monday, May 11, 2009

30m MEPT

As promised, here is a first impression of the 30m MEPT (Manned Experimental Propagation Transmitter).

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).