PURPOSE: To expand the degree of freedom of the layout of a BS antenna or the like by devising the system such that an intermediate frequency signal passes through a building part with radio wave propagation by a couple of relay antennas located outdoor and indoor with the building part made of a nonconductive plate separating the indoor and the outdoor inbetween.

CONSTITUTION: A couple of relay couplers 5 are opposed to each other with a window glass 6 inbetween, and a relay antenna 7 of an outdoor relay coupler 5 and a relay antenna 7 of an indoor relay coupler 5 are made opposite to each other. Thus, an output signal of a converter 2 is relayed from the outdoor relay antenna 7 to the indoor relay antenna 7 and the output signal of the converter 2 is sent to a BS tuner 4 through a coaxial cable 10. Moreover, an output signal of the BS tuner 4 is fed to a television receiver 11. Thus, the installed location of the outdoor BS antenna 1 and the indoor BS tuner 4 has a remarkable degree of freedom and the reception sensitivity of the BS antenna 1 is always improved.