It is not clear what you mean about the crystals in the transmitter and receiver not matching. The transmitter crystal is not the same as the reciever crystal (they cannot be interchanged) and are not exactly the same frequency if you are looking at the actual frequency in megacycles. The RC units are usually marked by a channel number (11 thru 60) for aircraft use. If your transmitter crystal is the same channel number as the receiver number you are okay, i.e. both marked channell 20 or XX you are okay. Any hobby shop should be able to explain that to you if you are still in doubt.