so it should be possible to send data only to a designated receiver module?
Yes and no...
When data is sent it is sent everywhere. It is up to the receiver to "decode" the signal. Even data that the receiver does not understand hits the receiver.

Think back to serial comms with wires. You have a "wait" for something before the receiver acts on the data. Pretty much the same with RF. But with RF there is noise from everywhere hitting the receiver.

Dig through the app notes from these folks
http://www.linxtechnologies.com/Supp...ication-Notes/
AN-00160
AN-00232
AN-00500
AN-00501
Are some good one to start with.