GB482717A - Improvements in radio direction finders - Google Patents

Abstract

482,717. Directive wireless signalling. HEFELE, E. J. Oct. 1, 1936, No. 26681, Convention date, Oct. 2, 1935. [Classes 39 (i) and 40 (v)] In a direction finder a directional antenna and a non-directional antenna are used for independently receiving the signals which are amplified and imposed upon the deflecting means of a cathode-ray tube. Fig. 5 shows a form of the invention employing superheterodyne reception. The balanced loop antenna 10 and the vertical antenna 11 are respectively connected to radio-frequency amplifiers 13<1>, 20<1>, both coupled to a common local oscillator 32. Condensers are provided for tuning the loop antenna and for bringing the signals applied to the two amplifiers to the same phase. The outputs from 13<1>, 20<1> are passed through intermediate frequency amplifiers 33, 34, and the two output voltages e<1>V, e<1>L are applied to the vertical and horizontal deflecting plates of the cathode-ray tube 17. If the input voltages are in phase, or 180‹ out of phase, the voltages e<1>V and e<1>L will be in corresponding phase and the trace on the cathode-ray tube will be a straight line, the inclination depending upon the relative values of the two inputs and their phase relationship. Movement of the directional aerial may thus be arranged to give a right or left indication. A reversing switch may be placed in the loop antenna connections to give a 180‹ phase-change so as to indicate correctly when the receiver is approaching or leaving the transmitter. If the gain of both amplifiers is controlled by A.V.C. potentials derived from the non-directional receiver, the indicator may be calibrated to read actual degrees " off course '' by means of a manual gain control in the loop amplifier. A reception unit 30 may be used for listening to signals. This comprises an anode-bend detector loosely coupled to the output of the non-directional amplifier, Fig. 7 (not shown), followed by an audio-frequency amplifier. A series resonant circuit is provided to exclude the I.F. frequency from the L.F. circuits. Fig. 10 shows a cathode-ray tube which is bent to economize space, the beam being deflected round the bend by plates 95 connected to the accelerating anode. To reduce electrostatic coupling, screens may be placed between the deflecting plates and between the deflecting plates and anode of the tube, Fig. 9 (not shown). A construction of stream-lined aerial is described, Fig. 6 (not shown). A cursor may be affixed to the screen of the cathode-ray tube, Fig. 4 (not shown), to facilitate flying along a predetermined course.