| 摘要 |
PURPOSE:To make a radio transmitter and receiver small-size and reduce the number of adjusted positions, by generating a transmission frequency signal by a direct oscillating variable frequency divider type synthesizer and by performing the frequency conversion of the transmission frequency signal to use it as a local oscillation frequency signal at the receiving time. CONSTITUTION:At the transmission time, the oscillation signal from a voltage control variable frequency oscillator 17 of a direct oscillating variable frequency divider type synthesizer 16 is modulated by a sound signal which passes through a microphone 3 and a momentary frequency shift control circuit 4, and this modulated signal is amplified by a power amplifier 6 and is transmitted through an antenna 8. At the receiving time, the output signal of the synthesizer 16 is subjected to frequency conversion by a frequency converting circuit 23, and the output signal from the circuit 23 is used as a local oscillation frequency to subject the receiving signal to frequency conversion in a frequency converting circuit 10, and the sound signal is outputted to a speaker 15 through a demodulating circuit 26. Thus, only a reference quartz oscillator 21 for transmission and a local oscillator 25 for receiving are used as quartz oscillators independently of the number of channels to reduce the number of adjusted positions, and therefore, a device suitable for the radio transmitter and receiver for multiple channels is obtained. |
