| 摘要 |
1,179,225. Testing radio receivers. RUMANIA, MINISTRY OF ELECTRICAL ENERGY. 11 April, 1968, No. 17684/68. Heading H4L. In a radio-telephone, means are provided for checking the operation of the receiver by utilizing some of the associated transmitter stages. Fig. 2 shows the crystal-controlled master oscillator stage T1, phase-modulating stage T2 and microphone amplifying stage T3, T4 of the transmitter which with switches r 1 , r 2 , r 3 on position a operates normally. With the switches in position b a feedback connection is provided from the anode of T4 to the control grid of T3 so that valves T3, T4 act as an audiofrequency oscillator and modulate the signal from T1 accordingly, the output of modulator T2 is disconnected from the subsequent transmitter stages and connected via a voltage divider R8, R9, filter A and adjustable attenuator B to the input R of the receiver, and the valves T1 to T4 are disconnected from the transmitter power supply and connected to the receiver power supply. The filter A selects a harmonic of the modulated wave from T2 which is equal to the frequency to which the receiver is tuned and which also provides the correct frequency deviation. |
