Those receivers are GARBAGE.
I recently conducted a test using an Arduino as sender and receiver. The range with those cheap green transmitters was nothing short of abysmal, with or without an antenna. I did not see range exceeding 100' (this is with 3.3v on transmit and receiver, since the project was for battery operation) - while with the $2 each RXB-12 receiver (and the same cheapo green transmitter, both with a quarter wavelength wire, clipped from an old network cable, as an antenna), under the same conditions, got me 1250'. Best of all, they're direct plug-and-play replacement for the crappy green ones.