Again, it depends. The PDA and J-box can work with either conventional AquaLink firmware or the PDA-specific firmware. You'll need to pull the PCB out and look at the chip/card on the back and see what version it has. There might be some way to check the firmware through the PDA itself but I have no idea how to do that.
If you look at the chip and it says Rev R or later, you're good to go with just the antenna (IQ30-A). If it's PDA firmware or if it's something less than Revision R, you'll need the whole IQ30-RS kit which includes the jbox antenna and the new PCB.