| 摘要 |
PURPOSE:To eliminate the effect of unnecessary radiation of a local oscillation section on other radio equipment, by designating an intermediate frequency as an odd number multiple of a half of the frequency interval. CONSTITUTION:The intermediate frequency, fit=(2K-1)Xfch/2 is used, where fit is the intermediate frequency of a superheterodyne reception section, fch is the frequency interval of a radio frequency and K is a natural number. The reception wave caught on an antenna 10 is supplied to a reception mixer 12 of the reception section 1 with an antenna changeover switch 11. The mixer 12 mixes the reception wave with a local oscillation wave of a local oscillation section 2 to obtain the intermediate frequency signal. An unnecessary signal is eliminated from the intermediate frequency signal with an intermediate frequency filter 13, after the result is amplifier at an intermediate frequency amplifier 14, and demodulated at a demodulator 15. The demodulated signal is amplified at a low frequency amplifier 16 and outputted as sound from a speaker 17. A local oscillation frequency fL is placed between radio channels f2 and f3. When the reception frequency is shifted by a half of the frequency interval, the attenuation of about 70dB is obtained normally. |
