I know, that's why I said use the USART and pick the byte up after it appears in the buffer. HSERIN is no better than SERIN, SERIN2 or DEBUGIN, it just uses the Hardware, but as for the rest, has the same disfunctionality with noisy reception.

Using FM instead of AM helps at the extremes of range, but the real answer is don't operate at the extreme edge! If you're operating your robot (or model boat or plane or Mars Lander) right at the edge of reliable communications, then it's time you upgraded to a better Radio Link otherwise you'll lose your boat or plane or Martian explorer. Get a better receiver, one with a better signal-to-noise ratio, up the power of your transmitter, improve your aerials, do I need to go on and state all the obvious choices?