A phasor is a network of capacitors and variable inductors used to adjust the relative amplitude and phase of the current being distributed to each tower in a directional array. A typical phasor has separate controls to adjust the phase of the current going to each tower, adjustable power divider controls, and a common point impedance matching network to adjust the system input impedance to 50 ohms with no reactance without disturbing the phase or amplitude of the tower currents.
References
Phasor (radio broadcasting) Wikipedia(Text) CC BY-SA