| 摘要 |
<p>PURPOSE:To prevent the adverse effect due to a leakage electric field by measuring an electric field strength due to an electromagnetic wave generated in the circumference when the electromagnetic wave is transmitted in a prescribed direction and by controlling a transmission electromagnetic wave so that a value obtained by the measurement be a prescribed value or below. CONSTITUTION:When an electric field strength exceeds a reference value, the maximum output within the reference value can be obtained by making small a pulse width 31 of a transmission pulse supplied from a transmission circuit 4 to a transmission antenna 2, by lowering a pulse voltage 32, or by making a repetition interval 33 of a pulse long. In the case when the result of measurement of the electric field strength is lower considerably than the reference value, the maximum output within the reference value can be obtained by widening the pulse width 31, by making the pulse voltage 32 high, or by shortening the repetition interval of the pulse. This adjustment of the electric field strength is conducted beforehand prior to the start of a finding operation, and it is preferable at first to adjust the electric field strength while transmitting an electromagnetic wave of low electric field strength into the ground.</p> |
