We claim the ornamental design for a radio remote control unit, as shown and described.
FIG. 1 is a perspective view of a radio remote control unit showing our new design;
FIG. 2 is a front elevational view thereof;
FIGS. 3 is a rear elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The evenly dashed broken line representations of items in the figures are included for the purpose of illustrating the unclaimed portions of the article that form no part of the claimed design.