If I'm not mistaken, the RF portion of those is the garbage superregenerative design like the cheap green OOK receivers, just piped to that chip to decode it.
Those receivers are garbage (the problem is the receiver, not the transmitter - I tested a bunch of transmitters, and a bunch of receivers. The transmitters made much less difference than the receivers). Unfortunately, your boards have the receiver and the decoder integrated on the same board, so it's somewhat awkward to use a better receiver (like a superhet design based on, say, the Synoxo SYN470/SYN480 chip - as available on the RXB12 boards that sell for a buck or so on ebay).