695,326. Radio transmitting and receiving apparatus; valve super-regenerative circuits. BENOIT, J., and SZEPESI, Z. May 18, 1951 [May 26, 1950], No. 11703/51. Class 40 (v). A portable short-wave transmitter-receiver comprises a crystal-controlled oscillator for transmission, and a super-regenerative receiver, the crystal being short-circuited during reception. With the send-receive switches at E the transmitter comprises an oscillator T1 controlled by the crystal 14, followed by a high-frequency amplifier T2. The grid of the modulating valve T3 is connected to a piezo-electric throat microphone 33 and the output from T3 is amplified by the valve T4 and modulates the screen of valve T2. The headset 30 is connected via capacitor 76 to the anode of valve T4 to provide sidetone. With the send-receive switches at R the crystal 14 is short-circuited and the screen grid of T1 disconnected, and the receiver comprises the valve T2 which becomes a high-frequency oscillator interrupted by means of the grid circuit which has a time constant dependent on the resistor 19, inductance 20, and capacitor 21, the inductance 20 preventing the grid from being earthed for highfrequency through the capacitor 21. The aerial 11 is connected to the anode of valve T2 and the detected signal appears across the inductance 23, is amplified by valves T3 and T4, and applied to the headset 30 via transformer 31. In an alternative arrangement, Fig. 7 (not shown), the functions of high-frequency amplifier for transmission and super-regenerative detector for reception are carried out by separate valves. Power is provided by a twovolt accumulator 40, a series resistor 41SP1/SP dropping the voltage to 1.4 volts for the heaters, and a vibrator 43 providing the H.T. An additional winding on the transformer 44 provides through a rectifier 56 a negative voltage to bias the valve T4. The accumulator can be recharged without removing it from the case by connecting the charger to a coaxial attachment 97 and operating the switch 92. The apparatus fits into a small metal box and is fastened by straps into a shelf-like carrier of aluminium which is attached to the chest of the operator, the rod aerial being arranged well clear of the operator's body.
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