PURPOSE: To transmit underground information to on-ground in the form of an electric signal by making a long hole on the circumferential face of a metallic cylinder in the axial direction, filling an insulator to apply mechanical reinforcement, applying a voltage between metallic cylinders so as to radiate an electromagnetic wave.
CONSTITUTION: A sensor 19, a modulation section 18 applying phase conversion to a digital data and a feeding section 17 radiating a modulated output as an electromagnetic wave are contained in a conductive transmitter case 12 in a drill collar 5. As for the case 12, an upper part 12a and a main part 12b are connected through a insulating ring 14. The upper part 12a and the drill collar 5 are connected electrically. The electrode of the feeding section 17 is connected respectively to the upper end 12a and the main part 12b. In applying a voltage from the feeding section 17 between the main part 12b, the upper part 12a of the case 12 and the drill collar 5, an electromagnetic wave is radiated. The torque exerted to the upper side of the drill collar 5 is delivered to the lower side from the hole 11 (bit side), but the insulator 13 is packed in the hole 11 and the hole is long, the force exerted to the insulator 13b is dispersed.
INOUE SATORU
SANEMORI AKIRO
