GB552068A - Improvements in radio telegraphy - Google Patents

Abstract

552,068. Wireless signalling. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Nov. 24, 1941, No. 15139. Convention date, Nov. 23, 1940. [Class 40 (v)] In transmitting telegraph and like signals by the use of different marking and spacing frequencies, multi-path distortion due to reflection and echo effects is reduced by arranging for a transient overswing of frequency at the beginning of each mark and space, as indicated in Fig. 4 in which ordinates represent frequency and abscissae time. The keying device 1, Fig. 6a, may be connected to the frequency-changing transmitter 3 through a condenser-shunted resistance 2, so that a square-topped D.C. voltage at 1 is converted to a voltage across 5 of the shape shown in Fig. 4. An alternative arrangement comprises a series resistance between a and b, and a shunt at b comprises a resistance and inductance in series Fig. 6b (not shown). When the keyed voltage is alternating, the source 11 is connected to the transmitter 3 through a series resistance R<1>, Fig. 7a, and a series-tuned shunt path comprising resistance R<11> capacity C and inductance L. The shunt path may be replaced by a parallel-tuned circuit in series with the resistance R<1>, Fig. 7b (not shown). At the receiver distortion due to the overswing is corrected by connecting between the. detector 7 and the utilization device 9 an inductance and a resistance in parallel as shown in Fig. 8a, or a network comprising a series resistance, and a seriesconnected condenser and resistance in shunt, Fig. 8b (not shown). For receiving alternating current signals, networks comprising parallel-tuned shunt circuits, or series-tuned series circuits are employed, Fig. 9a and 9b, (not shown).