Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html
A 23A battery will not be any better than a PP3 battery for a start, not enough current capacity.
A voltage divider will not provide you with a regulated supply that the Arduino requires.
Can you post the specs/data of the 315MHz tx/rx, I don't think it will withstand 12V supply.
Tom.. 