The ornamental design for a wirelesstransmitter, as shown and described.
FIG. 1 is a perspective view of a wireless transmitter showing my new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines shown unclaimed portions of the wireless transmitter and form no part of the claimed design. The portion that is broken and bracketed is intended to designate indeterminate length and forms no part of the claimed design.