| 摘要 |
1,135,889. Filter networks. HAZELTINE CORP. 25 Sept., 1967 [5 Oct., 1966], No. 2713/68. Divided out of 1,135,888. Heading H3U. Two circuits operative over different frequency bands are connected by a resistance device including a body of lossy dielectric material and providing a high resistance in the higher band and a low resistance in the lower band. As shown, the two circuits are the UHF tank circuit 13, 14 and the VHF tank circuit 15, 17 of the local oscillator of a television receiver and are tunable by a slider movable along first one and then the other coil. The device 18 has a low resistance in the VHF band and allows the VHF circuit to be effective but at UHF the VHF circuit is ineffective because of the high resistance of the device 18. The feedback through capacitor 20 is augmented at VHF by feedback through a circuit 21 which in the UHF acts like a choke and provides no coupling. The device 18 also serves to damp spurious resonances in the VHF circuit when the oscillator is operating at UHF. |
