GB1313019A - Antenna - Google Patents

Abstract

1313019 Aerials JFD ELECTRONICS CORP 19 Aug 1971 [28 June 1971] 38897/71 Heading H4A An aerial comprises a thin, flat, elongated member and a thin insulating substrate upon which it is mounted. There are two spacedapart gaps along the length of the member, which are bridged by resistors, and two output terminals. Amplifier means is also mounted on the substrate, and its input terminals are coupled to the said two output terminals. The resistors enable the aerial and the amplifier to be substantially matched over the operating frequency range. As described, an aerial 10, Fig. 1, for operation in the three bands 54-88 MHz (low V.H.F.), 174-218 MHz (high V.H.F.) and 470-890 MHz (U.H.F.) comprises a thin insulating substrate 11 upon which conductive coatings constituting aerial elements are deposited or otherwise formed. A high V.H.F. dipole comprises arms 13a, 13b having capacitive loads 22a, 22b at their outer ends, and L- shaped sections 15a, 15b at their inner ends. The dipole is connected to terminals 14a, 14b and, through capacitors 18a, 18b, to shunt feed points along an adjacent low V.H.F. dipole. Two V.H.F. directors 23, 24 are provided, the latter carrying a centrally-disposed strip 19. The low V.H.F. dipole arms comprise first meandering portions 17a, 17b, extending from the strip 19, gaps bridged by resistors 20a, 20b, second meandering portions 21a, 21b, and capacitive end loads 22a, 22b. Two V.H.F. reflectors 25, 26 with enlarged ends 25a-25b and 26a-26b are provided. The U.H.F. section of the aerial comprises three dipoles 51, 52, 53 which are coupled through pairs of strips 55, 56, 57 to terminals 54, and a director 58. An amplifier of printed circuit construction, as indicated by the outline 16, is mounted under the substrate 11, which is first sandwiched between two flat resilient insulating sheets 69, 70, Fig. 5, and is then installed in a housing assembly 60, having upper and lower lightweight moulded plastics portions 61, 62. The portion 61 has a downwardly directed marginal lip 61a which extends around the portion 62, and may be sealed thereto. The amplifier is secured to the portion 62, and connection to external equipment is made by means of a cable which passes through a hole in said portion to a connector 34. Three fixing points are arranged around the housing 60, and brackets 75a-75c may be secured thereto. The assembly may be erected on top of a pole (Figs. 4, 4a, not shown). In one embodiment, an amplifier 40, Fig. 2, has input terminals 42, 43 for the V.H.F. signals, which are separated by filtering circuits into the high and low bands, and are then amplified by means of respective transistors Q1, Q2. The output signals from the transistor circuits are recombined, and are associated with unamplified signals from the U.H.F. section of the aerial, from input terminals 44, by means of a balun B1, with output to the connector 34. The cable to the said connector also feeds in power at mains frequency, which is rectified by a diode D1, and is smoothed to supply the transistors Q1, Q2. The circuitry of apparatus for connection to the cable, which supplies the said mains power and separates the V.H.F. and U.H.F. signals, is described (Fig. 3, not shown). In another embodiment, the amplifier includes a third transistor, which is used for amplifying the U.H.F. signals, and power for the said transistors is fed in by the cable in direct-current form (Fig. 2a, not shown). The Specification makes reference to divisional Specification 1,313,020.