Antenna switch circuit

PURPOSE:To enable to prevent the deterioration of a diode at earth side and the deterioration of transmission power, by providing a constant current source and the diode which are started at reception in the path of a front end of a reception circuit from a 1/4 wave length coaxial cable. CONSTITUTION:In a path from a coaxial cable 6 to a front end of a reception circuit of an antenna switch circuit of a radio set of press-tall type consisting of a 1/4 wave length coaxial cable 6, diodes 5, 7 and costant current source 3 started at transmission, a constant current source 13 and a diode 15 started at the reception are provided. Further, at reception a constant current flows to a coreless coil 11 constituting a resonance circuit of front end of the reception circuit to conduct the diode 15, and at transmission the diode 15 is non-conductive to strengthen the isolation between a transmission circuit and a reception circuit.