The purpose of the beads is to keep common mode RF current off of the control lines.
The first line of defense is to place the beads at the transmitter end. However, depending on line lengths, shielding, grounding, termination impedances, and transmitter antenna placement, common mode currents can still be introduced into the interconnections. A best practice is to provide suppression at both ends of the cable.
It should also be noted that the ferrite material selection is important. It must have adequate suppression properties at the frequency of operation. But care must be taken that it does not provide any significant suppression at the frequencies used in the control cable.