In a transmission signal generating apparatus according to the present invention, a voice signal is amplified by a variable amplifier which varies its amplification factor in accordance with an amplitude control signal, and the amplitude of the voice signal output from the variable amplifier is limited by a variable limiter which varies its amplitude limiting range in accordance with the amplitude control signal. The thus amplified and amplitude-limited voice signal is supplied as a modulating signal to a voltage controlled oscillator constituting part of a PLL circuit which generates a transmission signal. A control signal generating section generates the amplitude control signal for the variable amplifier and the variable limiter by detecting the f/v sensitivity of the voltage controlled oscillator based on an output of a low pass filter constituting part of the PLL circuit.