GB604255A - Improvements in radio receiving installations - Google Patents

Abstract

604,255. Wireless receiving systems. PHILIPS LAMPS, Ltd. Dec. 6, 1945, No. 33013. Convention date, July 31, 1940. [Classes 40 (v) and 40 (vi)] In a diversity reception system, selection of the channel carrying the strongest signal is effected by obtaining from each receiver a direct voltage dependent on the carrier strength and feeding the direct voltages to the anodes and cathodes of a corresponding number of diodes having the cathodes connected to earth through a common resistance, the voltage differences then appearing between the respective anodes and being used to effect the selection of the desired channel. The apparatus at the central station for selecting the strongest signal from three separated receivers is shown in Fig. 2. Direct voltages derived from the A.V.C. circuits and dependent on the carrier strengths of the signals at the respective receivers are fed to terminals 11, 12, 13 and the corresponding audio-frequency signals are fed to terminals 11<1>, 12<1>, 13<1>, the arrangement being such that the largest direct voltage operates the corresponding relay 32, 33 or 34 to pass the strongest of the three signals to the output circuit 35. The direct voltages are fed to the anodes 14, 15, 16 of a tripole diode, the common cathode 17 of which is connected by a large resistance 18 to earth. Only the anode having the largest voltage will be operative and the cathode will assume the voltage of this anode. Thus, the anodes will assume the same relative potentials as the lines 11, 12 and 13 and these potentials are transferred through resistances 29 ... 31 to the grids of three valves 22 ... 24, the cathodes of which are connected to earth through resistance 25 and in whose anode circuits are the relays 32 ... 34. The valves 22 ... 24 are arranged so that the grid of each valve is connected to the anodes of the other two by a resistance R and thus only the valve with the highest grid potential conducts to operate the corresponding relay 32 ... 34 and so connect the strongest signal from lines 11<1>, 12<1>, 13<1> to output terminals 35. Neon tubes 36 ... 38 indicate which relay is energized at a given time.