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Problem of speech pulling and its implementation for the design of phase-locked SSB radio systems

Research output: Contribution to journalArticle

Original languageEnglish
Pages361 - 369
Number of pages9
JournalIEE Proceedings F (Communications, Radar and Signal Processing)
Journal publication dateNov 1981
Volume128
Journal issue6
StatePublished

Abstract

In the paper, the effect of speech interference on the performance of long-loop phase-locked VHF SSB radio systems is evaluated. It is shown that unless the system's reference tone is adequately protected by suitable filtering in the transmitter's audio processing, the problem of 'speech pulling' may occur with severe degradation in intelligibility. Furthermore, residual FM modulation of the VCO's control line (the first local oscillator) through speech interference degrades the oscillator's output spectrum with possible reduction in adjacent-channel rejection. After analysing the effect of interfering sinusoidal signals on in-lock-loop performance, filter design criteria are established for pilot-carrier and in-band-tone SSB systems, and the theoretically predicted results are verified experimentally. Finally, alternate phase-locked receiver configurations are suggested in an attempt to overcome first-oscillator spectrum degradation in long-loop receivers

Additional information

Publisher: Institution of Electrical Engineers (IEE) Rose publication type: Journal article Sponsorship: The authors are grateful to Prof. W. Gosling for his continued support during this project and to G. Lightfoot who has conducted extensive field testing of the tone-in-band system at 86 MHz. A. Lymer is grateful to the UK Science & Engineering Research Council for the award of a CASE research studentship which was supported by the GEC- Marconi Co. Ltd

Research areas

  • radiocommunication, interference

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