Those receivers are trash.
Search eBay for rxb12 or rxb14, the ones with the yellow pcb material (some with red look like good ones in the photos, but arent), get one of those. They're about a buck shipped, and the range is much, much better. Those transmitters are fine - not the best, but not trash. But those receivers are crap.
I got like 10 meters tops with those receivers, vs hundreds of meters with rxb12