| 摘要 |
PURPOSE:To attain broad band with simple constitution by replacing part or all of tuning capacitors into varactor diodes and changing the terminal voltage. CONSTITUTION:Transistors TRs 6-8 are switched by using a channel switching signal from a CPU 9 to split a required band. When a switching signal is outputted to a channel switching signal output terminal 10, the TR 6 is turned on and a DC voltage preset by a variable resistor 13 is fed to the variable capacitor 4, the tuning capacitor is changed to tune the loop antenna 1. The TRs 7, 8 are turned on by a signal from output terminals 11,12, the preset DC voltage of the variable resistors 14, 15 is fed similarly to the variable capacitor 4 to tune the loop antenna. The TRs 6-8 are used to switch the DC voltage fed to the variable capacitor 4 to change the tuning capacitor. Thus, the broad band is attained with simple constitution.
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