Abstract: A power antenna for automatically stopping an electric motor when a telescoping trouble occurs with the antenna to thereby cause a load of more than a predetermined magnitude to be applied to the electric motor and preventing the electric motor from being burned out and a telescoping operating mechanism from getting damaged, whereby the occurrence of an erroneous operation of the antenna such as repeated contracting and expanding operations thereof can be controlled. A worm wheel (2) inside an antenna mechanism is pivotally supported in such a manner as to slide in an axial direction and an engagement groove (21) is formed in an annular fashion, and an operating portion (32) of a movable body (17) of a limit switch (30) provided in a driving circuit for the motor is brought into engagement with the engagement groove (21) of the worm wheel.

Abstract: A roof antenna capable of receiving three kinds of bands, i.e., a FM radio band, an AM radio band, and a wireless-telephone band, includes an antenna element 10 having a structure that a conductor 15 winds around the insulator 16 in the form of a coil. A molded portion 14 is formed at the bottom of the antenna element, in which a trap coil is inserted. The electric length from the antenna top 11 to the internal metal fitting 17 at the lower end of the antenna element 10 is about a quarter of a FM radio wave. The electric length from the internal metal fitting 17 to the lower end of the trap coil 12 is about a quarter of a wireless telephone wave. A cover 19 supporting a basal part of the antenna element installs the first substrate 20 and the second substrate 21. The first substrate 20 and the second substrate 21 have a matching circuit, branching filters, and amplifiers.

Abstract: A device for automatically expanding and contracting an antenna having a rotary member for moving a flexible rodlike member that is coupled to the antenna for expanding and contracting the antenna. A worm is driven by a motor to rotate about a motor axis and an intermediate gear unit having a worm wheel is formed unitarily with a small diameter gear, the worm wheel being engaged with the worm and the small diameter gear being engaged with the rotary member for rotatably driving the rotary member. A gear unit support frame is provided for supporting the intermediate gear unit and a support shaft is fixed to a casing member and coupled to the intermediate gear unit, the intermediate gear unit and the gear unit support frame being axially movable along the support shaft in a direction substantially perpendicular to the motor axis.

Abstract: In an electrically powered mechanism for expanding and contracting antenna in which an operation strip coupled to antenna overcoat members that are telescopically connected to expand or contract, is expanded or contracted by a rotary member driven by a motor, and the operation strip has a width greater than the thickness thereof, and has arcuate surfaces or flat surfaces; the rotary member is rotatably provided in a case body which is provided with an annular guide portion with a guide groove for guiding the operation strip to the side of the drum and to the side of the antenna overcoat members, and a strip-receiving groove is formed along said rotary member into which the operation strip is fitted; and the operation strip is fitted in a curved manner to the strip-receiving groove, and a torque for delivering or pulling the operation strip when the rotary member is roated is so selected as to produce a required holding force depending upon the thickness of the operation strip, the radius of curvature of the s