Okay so if my TX crystal is on 72 MHz band, I dont have to keep buying new crystals for the TX but I just have to buy new crystals only for the new reciver but I have to make sure its on 72MHz correct?

For example all i would buy for a new plane is a flight pack with a crystal like this(my reciever is low band)
http://www2.towerhobbies.com/cgi-bin...I=LXBFK7**&P=M


How would I know what number that receiver crystal is? for example 12.
I wont need 2 crystals one for TX one for RX but only for Rx (Reciever)

so all i have to keep buying for new planes is crystals only for the reciever never for the transmitter unless I descide to use a different frequency and band.