A radio signal transmitter for an audio source generator includes a
reception antenna for receiving a plurality of broadcasting signals, a
decision unit coupled to the reception antenna for determining
intensities of the plurality of broadcasting signals received by the
reception antenna, a selection unit coupled to the decision unit for
determining an operating frequency according to a decision result of the
decision unit, a modulation unit coupled to the selection unit and the
audio source generator for transforming an audio signal provided by the
audio source generator into a broadcasting signal according to the
operating frequency determined by the selection unit, and a transmission
antenna coupled to the modulation unit for emitting the broadcasting
signal outputted from the modulation unit in the air.