GB1110783A - Improvements relating to interrogating apparatus for determining the optimum frequency for radio communication - Google Patents

Abstract

1,110,783. Radio signalling; transistor pulseclipping circuits. E.M.I. COSSOR ELECTRONICS Ltd. 14 June, 1965 [13 June, 1964; 20 April, 1965], Nos. 24632/64 and 16674/65. Headings H3T and H4L. In an apparatus for determining the optimum carrier frequency for use in a radio transmission system, of the type disclosed in Specification 1,110,784 wherein a sequence of pulses of oscillations of differing frequency is sent from the transmitting end, receiving apparatus comprises means for detecting whether the ratio of the received pulse amplitude to the average signal level over a predetermined period exceeds or does not exceed a given value for the respective pulses in a sequence. This is achieved by the circuit of Fig. 5, the demodulated pulses being supplied to the junction of resistors 60, 64. Each pulse 48 has a duration of 50 to 250 Á. sees. and is allotted a 10 m. sees. interval during which it will be received, the 10 m. secs. intervals being spaced by 5 m. sees. intervals, Fig. 3 (not shown). At the beginning of each 10 m. sees. interval short pulses 44 discharge capacitors 61, 67 via transistors 62, 68 respectively and during the 10 m. sees. interval the incoming signal (including noise) is averaged by circuit 60, 61 and supplied to one terminal of a twostate circuit 69. A portion of the incoming signal as determined by potentiometer 65 is peak rectified by circuit 66, 67 and supplied to the other input terminal of circuit 69 so that circuit 69 will be in one state or the other in accordance with which of the input signals is the greater. The amplitude of the received pulses is also quantized and supplied to a display means, Fig. 4 (not shown), and the output of device 69 supplies an " inhibit " signal to block the display if the voltage across capacitor 61 is greater than that across capacitor 67. The " inhibit " signal is supplied via gate 70 controlled by pulses 42 at the end of the 10 m. seoa. interval.