mauried:
The data sheets for those cheap 433 Mhz transmitter / receivers are a bit confusing.
The 3 - 12 V spec applies to the Transmitter only.
The receiver needs 5V regulated and the super regen receivers (the ones without a crystal) are the most critical , voltage wise.
What's confusing? The datasheet does clearly say 3-12V for transmitter and 5V for receiver. (4.9V-5.1V in my datasheet)
I only mentioned powering the transmitter with 12V. I used 5V on my receivers, which suited the PIC chips that I used to control this system. (And the usual Arduino setup, of course, but I hadn't started using Arduinos when I built the alarm systems.)
But you raise a good point that I overlooked - DrAzzy used 3.3V on both ends. 