GB630399A - Improvements in and relating to multiplex radio stations operating as a network - Google Patents

Abstract

630,399. Multiplex radio signalling. SOC. FRANCAISE RADIO-ELECTRIQUE. Aug. 19, 1947, No. 23032. Convention date, Aug. 20, 1946. [Class 40 (v)] Relates to multiplex radio systems for communication between a number of stations operating as a network, and of the type in which channels occupy adjacent bands in the radiated spectrum. The speech channels are shifted to their final position by a plurality of modulation and heterodyne stages. In the embodiment described, the twelve telephony channels comprise microphones. Mi, the 0-4 Kc/s. outputs from which are transposed, by modulators T and carrier generators #1 ... #12, to the bands 60-64 kc/s.... 104-108 Kc/s., selected by filters F#1 ... F#12. These bands are then used to modulate generators P1 ... P12 which produce carriers of 6 Mc/s.... 11.5 Mc/s. respectively at 0.5 Mc/s. intervals, and the outputs of the modulators Mo are combined. The combined spectrum is transposed by 24 Mc/s. at t to produce a 30 ... 35.5 Mc/s. band which again modulates the main 270 Mc/s. carrier at E to produce the radiated spectrum of 12 modulated waves of 300, 300.5 ... 305.5 Mc/s., the carrier and lower sideband being suppressed. At the receiver the heterodyne oscillator H operates at 291 Mc/s. to obtain, from the incoming wave, the modulated frequencies 9, 9.5 ... 14.5 Mc/s. which are fed to the channel demodulators DM. These are supplied with the 6, 6.5 ... 11.5 Mc/s. carriers from the sources P1 ... P12 respectively to produce a common intermediate frequency of 3 Mc/s. in each channel which after demodulation at AD results in the recovery of the shifted speech bands 60-64 Kc/s.... 104- 108 Kc/s. Further mixing with sources #1 ... #12 respectively, recovers the 0-4 Kc/s. speech band for each channel which is fed to the reproducers C.