| 摘要 |
682,808. Cathode-ray oscillographs; modulation measurements. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. April 4, 1951 [July 7, 1950], No. 17095/50. Class 37. [Also in Groups XXXV and XL (c)] An automatic modulation control circuit for a carrier wave transmitter is provided with means for indicating or displaying the A.C. and the D.C. components of the rectified carrier wave. The transmitter output feeder 20 is connected to a rectifier 2 with a load impedance comprising a transformer 7 and a resistor 8. Output taken from the transformer secondary coil 11 and the resistor 8 feeds a second rectifier 14 and provides at 19 a control voltage which is used to prevent excessively deep modulation. The cathode of the diode 2 is earthed for carrier frequencies by a condenser 9, and the resistor 8 is shunted for signal frequencies by a condenser 10. The voltage across the impedances 7, 8 is taken through a lead 25 to a deflecting electrode of a double-beam C.R. tube 24 and displays the A.C. signal voltage W on its screen, the D.C. voltage being suppressed by a condenser 26. The voltage across the resistor 8 is transferred through the lead 23 to an electrode associated with the second beam of the C.R. tube, and displays the rectified carrier voltage as a line L. Suitable meters may be substituted for the C.R. tube. |
