There are two different antennas (SMA stub type) available in the RZ600 kit
Long Type: This is used only in conjunction with the AT86RF212 radio transceiver.
Short Type: This antenna is made for the 2.4GHz frequency band and can be used either on the AT86RF230 or AT86RF231 radio transceiver.
The antennas should be screwed onto the respective radio frequency board and gently tightened.