The crystal would have to be on the same channel as the Tx.
If you have €200 to spend you can get an excellent radio instead of that toy.
Have a look at this, it's only €89 w/ no servos, or €114 w/ 4 servos
http://www3.towerhobbies.com/cgi-bin...I=LXRXF3**&P=0
Or, you can get this one with no servos for €127 - with 4 servos for €146
http://www3.towerhobbies.com/cgi-bin...?&I=LXPZT8&P=0