Medium-frequency radio transmission system

A medium-frequency radio transmission system comprising:

• a receiving antenna for receiving an amplitude-modulated medium-frequency radio wave at an existing building rooftop;
• a booster connected to said antenna and comprising a phase shifter, a level regulator, and an impedance matching device for preventing oscillation;
• a first coupler connected to said booster for coupling the received medium-frequency radio wave to an existing distributing cable or distributing conductive piping, said distributing cable or distributing conductive piping being for transmitting the radio wave to a predetermined floor;
• a first pair of couplers composed of a second coupler and a third coupler and combined with a first interconnection line at the predetermined floor for linking said distributing cable or said distributing conductive piping to a first loop-like line;
• and
• a second pair of couplers composed of a fourth coupler and a fifth coupler and combined with a second interconnection line at another floor for linking the received medium-frequency radio wave with a second loop-like line, wherein said first and second loop-like lines are closed-loop conductors, said loop-like lines receiving and reradiating the medium-frequency radio wave, thereby enabling listening to an amplitude-modulated medium-frequency radio wave in an objective area of the predetermined floor, wherein said couplers comprise a ferrite core surrounding a primary line and a secondary line, wherein the amplitude-modulated medium-frequency radio wave is transmitted to the predetermined floor via an existing distributing cable or distributing conductive piping with said booster and said couplers including said interconnection lines.