4000 Mc/s time-division 23-channel radio relay system
01 January 1953
A p.p.m.-a.m. system in which 23 communication channels are provided by a pulse train composed of channel pulses 0.5 musec wide and a marker pulse 1.5 musec wide is about to go into service. At 0 db input speech level, the channel pulses are modulated 30%, giving a speech output level at the receiving end of 0 db. Max. permissible pulse modulation is 70%. The transmitter output power is 100 W and frequency stability is within plusmn200 kc/s. The transmitting valve is a magnetron, the receiver local oscillator a klystron. The i.f. band is 52.5plusmn4 Mc/s and the 9-stage i.f. amplifier provides a gain of 90 db. The aerial is a paraboloid of 180 cm dia. with a gain of 35 db and a beam angle of 3deg. Trials have been held over a 50 km range. With 10 relay stations the equipment can operate over a distance of 1000 km.