Have you read the data sheets on the different receivers to understand how they operate? Most, if not all will require a synchronizing stream of bits before any data can be decoded from the received RF signal. The data sheets will tell you what is required. If the receiver requirement and the transmitter requirements are not compatible, there will be no data or it will be miss-interpreted. The data part of the signal will likely be 8-bit, but will not have start-stop bits like async serial data.