WATERTIGHT ANTENNA SYSTEM

PROBLEM TO BE SOLVED: To provide a watertight antenna system which has such directivity that while watertightness is held, gravel flowing on a riverbed can be detected, and is easy to handle. SOLUTION: The watertight antenna system comprises a nonmetallic pipe which has both end portion closed in watertight structure, and a coaxial cable 203 is loaded in a watertight cylinder 202 disposed in water along its axis direction; and a conductor plate 207 made of a conductive plate member in an equilateral triangle shape is connected to an insertion tip portion of the coaxial cable 203 loaded in the watertight cylinder 202, and a radio wave absorption layer 208 is formed around the outer periphery of the coaxial cable 203 in the watertight cylinder 202. A vertical angle of the conductor plate 207 is connected to a center conductor 203a of the coaxial cable 203, the base of the conductor plate 207 and an external conductor 203b of the coaxial cable 203 are connected through a resistor 209, and the hypotenuse of the conductor plate 207 is disposed toward a vertical direction. COPYRIGHT: (C)2009,JPO&INPIT