GB529103A - Improvements in or relating to wireless transmitting and receiving systems for two-way operation - Google Patents

Abstract

529,103. Duplex wireless signalling; frequency and phase modulation. PERCIVAL, W. S. May 12, 1939, No. 14242. [Class 40 (v)] In combined wireless transmitter and receiver apparatus for two-way operation employing frequency or phase modulation, the transmitter oscillator is employed as a local oscillator for the adjacent receiver. As shown in Fig. 1, a common aerial is employed for the transmitter 1 and the receiver 2. The transmitter may generate a 250 m.c. wave which is fed to the aerial through a filter circuit designed to present low impedance to the transmitted wave but high impedance to the 245 m.c. received waves. The aerial is connected to the receiver 2 through another filter circuit which readily passes the received wave, but allows only a suitable fraction of the transmitter energy to reach the receiver and set up therein a 5 m.c. intermediate frequency. The distant station has a similar circuit arrangement, but the transmitter is tuned to 245 m.c. and the receiver to 250 m.c. Separate aerials may be associated with each transmitter and receiver, the local oscillation for the receiver being radiated from the adjacent transmitter. Depth of modulation in a transmitter may be indicated in the adjacent receiver; or if desired the signals from the adjacent transmitter may be balanced out in the detected output of the receiver. Both transmitters may be provided with suitable means for stabilizing their frequencies; or one transmitter only may be directly stabilized, the other being adjusted by means responsive to changes in the intermediate frequency in the adjacent receiver. In a third arrangement neither frequency is directly stabilized, but AFC means are provided for maintaining a constant difference between them. Specification 170,154, [Class 40 (v)], is referred to.