| 摘要 |
PURPOSE:To obtain stable input matching characteristics and good noise factor characteristics, by providing a by-pass circuit in parallel to a halving circuit of an antenna switching circuit and thereby eliminating the use of unstable halving circuit in a VTR mode. CONSTITUTION:Input signal from a TV antenna is halved by an halving circuit 1. A signal outputted from an output terminal 3 is inputted to a built-in tuner 5 of VTR, stored in the tape of VTR, and an output signal from a terminal 4 is added to the terminal 9 of a switching circuit 7. A signal from the terminal 9 and a signal from an RF modulater 11 are switched and selected electronically by the circuit 7, and inputted to a TV receiver from a terminal 8. A by-pass circuit 13 is provided in parallel to the halving circuit 1, and a switch 17 linked with the switch 16 of the circuit 7 is provided in the circuit 13. When the switch 16 is made to VTR mode, the halving circuit 1 is by-passed by the switch 17 and unstable halving circuit 1 is not used. Thus, input matching characteristics and noise factor characteristics are improved. |
