Running RF link at high voltage

The pages for the 315 MHz and 434 MHz RF link transmitters say that the working voltage is 3-12VDC, and that higher voltages mean longer range. Suppose I to maximize range, is it possible to supply 12VDC to the Vcc pin but supply data at 3.3V levels? Or do I have to step up data to Vcc levels?

You may have a try, but be careful not connect to 12VDC through an 110V or 220V to 12V adapter. It’s easy to burn down the transmitter.
It is said that it’s ok to use 12VDC from batteries.