GB1368466A - Automatic radio direction finders - Google Patents

Abstract

1368466 Radio direction-finders; aerials MARCONI CO Ltd 6 March 1972 [7 April 1971] 8944/71 Headings H4D and H4A An automatic radio direction finder comprises an aerial system of orientable directivity, an open aerial, means for combining signals from said aerial system and said open aerial, and means for employing said combined signals to orientate the directivity of said aerial system. There are also provided means for subjecting the signals from the orientable directivity aerial system to automatic gain control before combining them with the signals from the open aerial, and an additional member, with directivity substantially perpendicular to that of said aerial system, for supplying communication signals to a separate channel. As described, a streamlined housing 1 of insulating material, which is suitable for fitting to an aircraft, contains two mutually perpendicular loop aerials 2, 3 with ferrite cores. An open aerial is provided by a thin metal plate 4 fitted on an outside face of the housing 1. The two aerials 2, 3 are fixed, and are connected to respective stator coils 8, 9 of a radio-goniometer by leads 5, 6. The rotor of the goniometer has two mutually perpendicular coils 10, 11 and is rotatable by a two-phase motor 12 (alternatively, the loop aerials 2, 3 could be arranged to be rotatable). The coil 10 is coupled through an amplifier 13 to a balanced modulator 14. A switching oscillator 15 supplies one phase of the motor 12 and also the balanced modulator 14, output from the latter being combined with signals from the aerial 4 in a coupling amplifier 16. A mixing stage 17, with which is associated a local oscillator 18, follows the amplifier 16 and produces an I.F. signal which is fed via an amplifier 19 to an automatic direction finder detector 20 and passed to an output amplifier 21 to supply the other phase of the motor 12. Output from the detector 20 is also fed to an automatic gain control detector 22, which is coupled to the amplifier 13. Output from the goniometer rotor coil 11 is fed via an amplifier 23 to a mixing stage 24, which is also associated with the local oscillator 18. The resulting I.F. signal is fed via an amplifier 25 to a detector 26, the output of which is taken to headphones 27. In operation, the motor 12 turns the goniometer rotor so that the coil 10 is in a null position, when the gain of the amplifier 13, and the output of the coil 11 have their maximum values.