Most of those RF modules use ASK. And generally, they don't need CRC bits (that's all up to you), but what they do need is manchester encoding (aka bi-phase encoding) to keep the internal data slicer from losing it's mind.
Search for and check that thread I mentioned earlier and you'll see. Basically, you end up cutting your data rate in half by changing all the 1's to '10' and 0's to '01'. Sounds silly but it works great.
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