For 433 mhz, the length of the wire should be around 35 cm, which is the length I had for the transmitter and receiver. I also had them on the same breadboard, so distance shouldn't have been a problem. I never got a single correct transmission. Whenever I measured the antenna's voltage with respect to ground it was always 0.000V and never changed. Even though I don't have an oscilloscope, I thought my digital multimeter would give me some kind of small reading at the antenna.