Wireless PIR Transmitter 433 Mhz

To return to the original question - why does the circuit as shown not work? I would suggest that Q6 is turning off too quickly to allow the 'reset' signal to be sent, probably because there is no base resistor on Q6 and the small capacitor is therefore discharging too quickly. Put a 1K resistor between the diode and the base and that should work, even with a small capacitor. The reason it works with a 3300μF capacitor is that this takes a lot longer to discharge!