GB679154A - Improvements in and relating to radio repeaters - Google Patents

Abstract

679,154. Radio signalling valve gating circuits. BRITISH COMMUNICATIONS CORPORATION, Ltd., and HEFTMAN, T. S. June 6, 1951 [March 6, 1950], No. 5632/50. Classes 40 (v) and 40 (vi). In a radio repeater system, the receiver 11, Fig. 1, and transmitter 12 of the repeater station are tuned to the same frequency and are rendered inoperative alternately, a device 16 being adapted to store signals received while the receiver is operative and to apply the stored signal to the transmitter during its operative interval. A frequency-changer 13 supplied by the receiver 11 and a local oscillator 14 feeds I.F. signals of a few hundred kc/s. into a delay line 16, the output of the line being fed into a second frequency changer 17 supplied from the local oscillator 14 so as to restore the frequency of the transmitter to that of the receiver. The output of the line 16 also feeds a switch device 18 which when signals exceed a predetermined amplitude appear in the line, switches off the receiver and switches on the transmitter so as to relay the signals in the line until the output ceases and the receiver and transmitter are again switched on and off respectively. The switch-devices 18, Fig. 2, comprise a pair of diodes 19, 20 reversely connected to the delay line 16. The diode 19 is biased by a battery 23 to render the receiver pentode 24 normally conducting but to prevent charging of the condenser 21 in response to noise. The diode 20 is rendered normally non-conducting by a battery 27 and the transmitter valve 28 which is connected to the frequency changer 17 through a resistor 29 is made normally non-conducting by a biasing battery 30. When signals in the delay line 16 exceed the bias on the diodes, the condensers 21, 25 are charged, the former rendering the valve 24 non-conducting and the latter opposing the bias provided by source 30 to render the valve 28 conducting. The delay-device may take the form of a column of mercury, the received signals being applied at one end through a piezo-electric crystal and picked up at the other end by a further crystal. The switching device 18 also may be in the form of a switch driven continuously.