prior art or in the above described embodiments further in these figures reference numeral 45 designates the base station device which includes the control circuit a 11 which controls the signal receiver a 7 the signal transmitter a 8 and the synthesizer a 10 and serves as an interface between the signal transmitter a 7 and the signal receiver a 8 and an external device further in the figures reference numerals 46 and 47 designate windings a and b of a hybrid transformer respectively 49 dc voltage supply terminals 50 signal cable connecting terminals 51 further in fig7 reference numeral designates a conical ground plate of a discone antenna and 52 control lines for making access to the control circuit a 11 in fig7 the antenna 6 39 and the conical ground plate 51 are aerial sections and external conductor 19 with the skirt as shown in fig6 are outside of a coaxial cable not shown the components 9 through 11 and 46 through 49 provided inside the external conductor a 19 form a radio section and the connecting terminals 50 form a connecting section the operation of the base station device shown in fig6 will now be described the length of the skirt a 20 is set to a quarter 1 4.