GB769067A - Improvements in or relating to monitoring means for reflector type aerials - Google Patents

Abstract

769,067. Testing aerial systems. STANDARD TELEPHONES & CABLES, Ltd. May 27, 1955 [May 28, 1954], No. 15431/55. Class 40(7) A monitoring arrangement for an aerial system having an extended metallic reflector comprises a cavity tunable to be resonant at the radiation frequency of the system disposed behind the reflector and coupled to the radiated energy through a suitable aperture. If the aerial system functions at a number of differing frequencies a plurality of cavities, one tuned to each frequency, may be provided coupled through separate apertures or through a joint aperture. The energy accepted by the or each resonant cavity is detected and applied to a meter or other device to provide an indication that radiation at 'the resonant frequency is. being effected. In the embodiment shown a paraboloidal reflector 2 of sheet metal or .wire mesh is energized by means of a dipole primary .element 8 backed by a disc and fed by means of a co-axial feeder 9. The primary element may be a waveguide horn if desired. The monitoring device comprises a tuned cavity 1 coupled to the radio field by means of aperture 3 and tuned to the correct frequency by plug 7. The energy accepted by the cavity is detected by a crystal rectifier connected to hair-pin lead 5 and feeding a meter. The reflector may form part of the wall of the cavity as shown or the cavity may be coupled to the aperture 3 by means of a tube. If this tube exceeds half an inch in length a loop or probe within the tube improves the coupling. The coupling aperture in the reflector have negligable effect on the radiation pattern as their dimensions are small compared with a wavelength. They may be protected by being filled or covered with dielectric material.