A radio communication apparatus capable of carrying out transmission and reception of signals at a time has a frequency synthesizer and a frequency modulator both in novel structures for removing interference between a local signal and a transmission signal. The frequency synthesizer has a local oscillator controlled by a first phase comparator for phase-comparing a frequency divided output of the local oscillator and a reference frequency signal to provide a local signal. The frequency division of the output of the local oscillator is effectd by a first frequency divider for dividing the frequency of the output of the local oscillator and a variable division ratio frequency divider for dividing the frequency of the output of the first frequency divider. The frequency modulator has a transmission oscillator controlled by a second phase comparator for phase-comparing the output of the first frequency divider and a frequency divided output of the transmission oscillator to provide a transmission signal. The frequency division of the output of the transmission oscillator is effected by a second frequency divider.