GB1226105A - - Google Patents

Abstract

1,226,105. Aerials; radio receiving apparatus. BRITISH BROADCASTING CORP. 7 June, 1968 [8 June, 1967], No. 26547/67. Headings H3Q and H4A. A directional radio receiving system comprises a multi-element aerial array in which each element is substantially alike and is coupled through an amplifier or other active device to common output terminals. The input impedance of each amplifier is arranged to be not less than twice the impedance of the associated aerial element, and it is stated that the effect of mutual impedances between the elements can thereby be made negligibly small, so reducing side-lobes and allowing operation over a wide band of frequencies. As described, each element of an eightelement array is in the form of a metal tube folded dipole having upper and lower limbs 10, 15, the former having within it an R.F. cable 11 connecting a socket 13, which is mounted on a metal block 14 welded to the dipole, to the output of a solid state amplifier 12. The said amplifier is wired to a printed circuit on a glass-fibre board and is housed within a metal tube 24. It has an input terminal 23 which is connected by means of a grub-screw 22 to one limb of the folded dipole, the other limb making connection with the tube 24. An insulating spacer 18 separates the limbs of the dipole, around which an insulating tube 19 is clamped by clips 20, 21. The output impedance of the amplifier 12 is arranged to match the impedance of the cable 11. Adjustable short-circuits 25 across the limbs of the dipole are provided for tuning out the total capacitance across the drive point at the centre frequency of operation.