[Al Skierkiewicz]

[R66]
A noise filter may be wired across motor leads or PWM leads. For the purposes of Inspection and rules compliance,such filters will not be considered custom circuits, and will not be considered a violation of Rule [R49] or Rule [R65].
Acceptable signal filters must be fully insulated and are:
A one microfarad (1 μF) or less non-polarized capacitor may be applied across the power leads of any motor on your Robot (as close to the actual motor leads as reasonably possible).
A resistor may be used as a shunt load for the PWM control signal feeding a servo.
It is not uncommon for servos to react to RF noise generated in the motors and motor wiring. It is best to run the PWM cables away from high current wiring and when it must cross, cross at right angles to minimize mutual coupling. the resistor lowers the impedance of the cable and generally, keeps the RF from overcoming the servo command signal.