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Title: A study of possible alternatives in the design and operation of medium wave broadcast receivers
Author: Mejallie, I. D.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1980
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Since the number of broadcast receivers always exceeds the number of transmitters providing the service, by a factor of 10 or more, the introduction of any alternative method of radio transmission compared to the conventional full-carrier double sideband amplitude modulation, will always depend on whether practical receivers are possible, rather than the feasibility and value of new transmission services. This thesis examines the technological implication of some new transmission scheme; namely, (i) having the two sidebands independently modulated, which implies the possibility of stereo AM, or SSB plus full carrier, (ii) adding low data rate digital signalling either to the carrier phase or as sub-audible tones. The technological implication to the radio station transmission are not severe, but as discussed in the thesis, the implications to possible receivers are severe and will predominate any discussion of new service introduction. Discussion in the thesis is supported by having, (i) a representative ISB transmission generator capable of providing independent left and right audio sideband signals with Z 40dB discrimination over the bandwidth 50-5000Hz, $ 40dB intermodulation, and tuneable over the MW band 522-1602kHz; (ii) a prototype digitally tuned MW receiver capable of ISB and conventional reception. The receiver is also novel by the fact that it tunes by channel (O-120 on the MW, 0-15 on the LW) and can also scan the bands electronically. Digital volume control is also included. Synchronous and envelope detection can also be compared. Results of observations made with the ISB transmitter and receiver operating as a pair are presented. An important result is that the non-linearity in a conventional AM receiver, which is not usually apparent to the listener of AM, now becomes a critical factor.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available