PURPOSE: To make it possible to provide a tuning circuit by which desired effective sensitivity can be expected to the post stage of an antenna by dividing the inductance of the tuning circuit into two or more and by selecting one of them corresponding to a reception frequency.

CONSTITUTION: To the post stage of artificial antenna ANTD composed of resistance R1, capacitors C1 and C2, and power supply VA (input voltage), the tuning circuit including varactor diode CV and divided inductaces L1 and L2 is connected. Between connection point J between L1 and L2, and the earth, switch S is provided which switches by an adequate switching signal. In this constitution, switch S is open in a middle-wave band of 535 920KHn to cause resonation with L1+L2 and closed between 920 and 1605KHz to cause resonation with only L1. As a result, the sensitivity-frequency characteristic curve approximates effective sensitivity and the inductance is further divided; and an adequate adjustment of the value makes it possible to obtain easily fixed effective sensitivity, and only the excellent part of diode Cv can be used.