| 摘要 |
PURPOSE:To receive a broad band including a CATV band, by adopting a 3- band switching system to an input tuning circuit section having a single tuning parallel resonance circuit. CONSTITUTION:Tuning coils L15, L16 and band changeover switching diodes DS6, DS7 and the like are added in an input tuning circuit section, an LPF of about 600MHz comprising coils L17, L18 and a capacitor C11 is inserted between this input tuning circuit and an IF filter section, and an antenna input signal is applied to the input tuning circuit from an antenna input terminal via an IF filter section and the LPF. Band changeover switching diodes DS1, DS6, DS7 and a DC changeover diode D4 are turned on and DC changeover diodes D1, D2 are cut off at the receiving of a B3 band, a single tuning parallel resonance circuit is formed, and a high band (M3 band) of 220-440MHz is received selectively. M2 band and M1 band are similarly received selectively. |
