Another (fainter) possibility is that you have a strong source of interference that is ‘swamping’ your rcvr, so that your signal isn’t seen amongst all the muck.
The frequencies used by these modules (434 and 315 Mhz) are used by lots of household gadgets, including garage-door openers, keyless entry systems for cars, etc.
Are you running 315 or 434? I think 315 is used by more cheap gadgets, and is more likely to see interference.
Try running the rcvr without an antenna wire connected (you should do that anyway until you get everything working). If you have an antenna wire connected, your rcvr is picking up everything within half a block or so… Maybe also try covering the rcvr with a metal box, to shield any unwanted signals.
Pete