GB556093A - Improvements in radio antennae - Google Patents

Abstract

556,093. Wireless aerials. STANDARD TELEPHONES & CABLES, Ltd. April 3, 1942, No. 4478. Convention date, April 9, 1941. [Class 40 (v)] A dipole radio antenna comprises, in the form shown in Fig. 1, hollow conductor means 10 extending in opposite directions from a feeding point, an inner conductor 11, 12 extending through the hollow conductor to points slightly beyond its ends, means, such as capacity plates 13, 14 for coupling the conductors 10 and 11, 12 at their ends, and means, shown as a transmission line section 17 with a short-circuiting bar 18, for supplying energy to the inner conductor at the feeding point. The curves 19 and 32 represent the current distributions along the conductor 10 when it is respectively a half wavelength and less than a half wavelength long. In a modification, the two halves of the conductor 10 are insulated from one another at the centre, giving rise to current nodes at the adjacent ends of the two halves and greater current at points towards the outer ends, which latter are also points of low voltage, so that large insulators are not needed for supporting the plates 13, 14. Fig. 3 shows another form giving substantially the same current distribution 22c, 22b without necessitating insulation between the two halves of the conductor 10, in which outer conductive sheaths 24, 25 are connected to the conductor at or near its ends and extend back towards the centre. The sheaths need not be continuous tubular members, but may consist of a number of wires, and they may extend only over a fraction of the distance to the centre of the conductor 10. Fig. 5 shows a dipole carried by a metal mast 30 to the top of which are attached the ends of the conductors 15, which form a transmission line terminated by a short-circuiting bar 31 and connected to the ends of the inner conductors 11, 12. These last are coupled by coils 13A, 14A to the ends of the tubular conductor 10C, 10D, where protective caps 34, 35 of insulating material are provided. A similar construction employing two dipoles and capacity couplings in place of the coils 13A, 13B is illustrated. The invention also comprises a similar construction of mast aerial, mounted directly on the earth and having an outer conducting sheath conductively connected to it at or near the top and extending downwardly. The sheath may be continuous, or formed by stay wires 47, Fig. 11, one or more of which may be connected through an impedance 50 to the earth. The high-frequency energy may be supplied to the adjacent ends of the hollow conductors forming the two halves of the dipole, or to the base of the hollow mast aerial, instead of to the inner conductor. Fig. 16 shows a hollow mast aerial 43 with an outer sheath formed by stay wires 47, and supplied at the base with energy from a source 60. The inner conductor is formed by a double transmissian line 41A, which is employed for supplying energy from a second source 70 to a short-wave radiator 72 mounted on the top of the capacity plate 42 by which the inner conductor is coupled to the end of the hollow mast. The effect of the inner conductor, as explained in the Specification, is to compensate for the high radiation of the large diameter hollow conductor or mast by supplying energy which reinforces the wave reflected from the outer end, so obtaining a symmetrical radiation pattern with well-defined nulls.