GB1263027A - Tunable aerials - Google Patents

Abstract

1,263,027. Aerials. PYE Ltd. 12 May, 1970. No. 22935/70. Heading H4A. In an aerial a variable inductance coil is connected between two radiating members. An insulating housing carriers or encloses the coil and one of the radiating members, the other radiating member being secured to it. Means for varying the inductance of the coil in order to tune the aerial comprises a ring which is slidable upon the housing. As described, a portable transmitter-receiver 2, Fig. 1, is connected via a flexible gooseneck section 3 to the lower end of an aerial 1. A tubular housing 6 made, for example, of resin bonded glass fibre, is sealed at its lower end by a ferrule 7, which provides means for attachment to the gooseneck section 3, and is sealed at its upper end by a ferrule 8, which provides means for attachment of a whip section 5 of the aerial 1. Located within and adjacent the upper end of the tube 6 is a coil 9 provided with a ferrite core 10. Said coil is connected to the ferrule 8 and to a radiating conductor 11, which extends to the ferrule 7. A tuning assembly 12 comprises an insulating material tube 13 having secured to its inner surface one or more rings 14 of a non-magnetic conductive material, such as aluminium. Said tuning assembly may be slid between an upper position, when the rings are closely coupled with the coil so that its inductance is reduced, and a lower position, where the coupling is minimal. The coil 9 may be wound upon a former in which is the core 10, in the form of a plurality of short sections placed end to end. Two collars may be cemented inside the tube 6, between which the coil and core assembly is retained together with a compression spring (Fig. 2, not shown). The tuning assembly 12 may be held in position by means of a spring- loaded lever mounted thereon which bears frictionally upon the outside of the tube 6, or a split collet chuck type device may be provided. The coil 9, and also the conductor 11, may be embedded within the wall of the tube 6. The rings 14 may be replaced by a single conductive cylinder of length equal to that of the coil 9, if maximum variation of inductance is required. In another embodiment, the tuning means is ferromagnetic, so that the inductance of the coil is increased (instead of decreased) as the tuning means is moved to encompass the coil. Specification 1,007,896 is mentioned.