I have stumbled upon this very cheap so called "crystal-less" RF transmitter: http://www.mouser.com/ds/2/368/Si4012-35123.pdf
It says there on page 5 the Carrier Frequency Accuracy is 250 ppm while crystal-less. Does this mean that for a 433 MHz carrier there will be 250 x 433 =
maximum drift above or below the nominal carrier frequency ? Does this look like enough for the FSK receiver not to be able to tell the signal any longer ? A few tips on how to program the receiver and whether or not I can get away with a non-crystal-less SiLabs paired receiver would help.