Version remaniée de: Diss.--Fakultät für Rechtswissenschaft--Universität Bielefeld, 1987.

Thesis (MScIng)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

The long term isolated pulsar monitoring program, which commenced in 1984 using the 26 m radio telescope at the Hartebeeshoek Radio Astronomy Observatory (HartRAO), has produced high resolution timing residual data over long timespans. This has enabled the analysis of observed spin down behaviour for 27 braking pulsars, most of which have dataspans longer than 14 years. The phenomenology of observed timing residuals of certain pulsars can be explained by pseudo periodic effects such as precession. Analytic and numerical models are developed to study the kinematic and dynamic behaviour of isolated but torqued precessing pulsars. The predicted timing residual behaviour of the models is characterised, and confronted with timing data from selected pulsars. Cyclic variations in the observed timing residuals of PSR B1642-03, PSR B1323-58 and PSR B1557-50 are fitted with a torqued precession model. The phenomenology of the observed timing behaviour of these pulsars can be explained by the precession models, but precise model fitting was not possible. This is not surprising given that the complexity of the pulsar systems is not completely described by the model. The extension of the pulsar monitoring program at HartRAO is used as motivation for the design and development of a new low cost, multi-purpose digital pulsar receiver. The instrument is implemented using a hybrid filterbank architecture, consisting of an analogue frontend and digital backend, to perform incoherent dedispersion. The design of a polyphase filtering system, which will consolidate multiple processing units into a single filtering solution, is discussed for future implementation.

This thesis reports on the design, construction, testing and operation of the spectral line and continuum receivers built for the 22 GHz Radio Telescope. First results from 'the telescope were obtained and have been analysed to give an estimate of system efficiency. Tests have been performed on the front end and in particular on the 22 GHz mixer in order to determine the minimum detectable temperature. The Sun, Moon and major planets are sources suitable for antenna alignment and consequently a literature survey of emission at 22 GHz from elements of the Solar system has been made.

The problem of data transmission in a packet radio system with one central base station and a number of mobile/stationary terminals is addressed. More specifically, the effects of possible collisions between packets on the inbound channel are investigated. Schemes which can be used to improve the performance are studied. The use of capture to improve the performance of slotted ALOHA systems is discussed. For a power group division scheme proposed by Metzner in which a capture effect is artificially induced, it is shown that in the two power group case, the higher power packet needs only be able to tolerate interference from up to three lower power packets in order to realize most of the achievable improvement of the infinite capture model. The evaluation of the performance for more than two power groups is also considered. A packet radio system in which a capture effect exists due to the fact that mobiles will generally be at different distances from the base station is also investigated. A number of different capture and spatial distribution models are discussed. Methods for evaluating the probability [formula omitted] of successful reception when there are [formula omitted] contending transmitters are examined. It is shown that a generalized capture model can be used to estimate [formula omitted] for an example system which uses non-coherent frequency shift keying modulation. This model can be applied to other systems as well. In most practical systems, the mobiles cannot get arbitrarily close to the base station. The effects of this constraint on [formula omitted] is examined. The dependence of the capture probability for a test mobile on its distance from the base station is also analyzed. The use of multiple directional antennas and receivers in a slotted ALOHA system in which the signals from the different transmitters are received with more or less the same powers is analyzed. It is shown that the performance of the system can be substantially improved by using directional antennas and multiple receivers. Results indicate that fewer than five antennas per receiver are required in order to achieve most of the achievable performance. A finite population Markov model is used to evaluate the performance of a multi-antenna and receiver slotted ALOHA system in a mobile radio environment in which the signal power levels from different mobiles are no longer equal. The effects of three different antenna patterns, background noise and Rayleigh fading are studied. Here again, numerical results indicate that substantial gains are possible with the use of several antennas and receivers. It is also found that the dynamic behaviour of the system is improved. The selection of the antennas to be connected to the receivers becomes an issue if the number of receivers at the base station is less than the number of antennas . Four antenna selection schemes are compared for three different channel models, assuming an ideal antenna pattern. It is found that the scheme which selects the antennas with the largest received signal powers is nearly optimum. The effects of using a more practical non-ideal antenna pattern are also discussed. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Radio broadcasting, from its inception, was recognized as a medium with educational possibilities. The decision of the Privy Council in 1931 to vest control of broadcasting in the federal government, therefore, invited Dominion participation in radio education. With the establishment of the CBC, and the implication that it was to develop radio's educational potential, the possibility of having national radio education became more real. National radio education developed in response to four general forces. First, as the depression closed, the CBC was able to stabilize its financial situation, evolve a policy on controversial programming, establish co-operative relations with certain voluntary educational associations, and sponsor a national investigation into school broadcasting. Second, the arrival of the Second World War created a fervent nationalistic feeling and provided the conditions for an increase in the power of the federal government. The result was an interventionist-nationalist policy, on the part of the Dominion Government, which found cultural expression in national radio education schemes, such as "Young Canada Listens" and "Farm Radio Forum." The third force involved in the development of national radio education was related to a general programme shift in Canadian broadcasting from light entertainment to a more serious fare. Besides the use of more abstract content, this programme shift was characterized by the creation of radio programmes to suit specific audience groups, various attempts to overcome the passivity of the radio audience and the use of the radio as a medium for artistic and creative expression. The growth of national radio education in the early 1940's both reflected this general programme shift and provided another channel within which it could be conveyed. Finally, national radio education developed because of a desire, on the part of provincial educational authorities, to co-operate with a federal agency, the CBC, in the production of educational broadcasts. This desire to co-operate stemmed, in part, from a renewed sense of confidence in the national broadcasting authority and a wish to secure the educational benefits presented by the radio. Co-operation was achieved eventually on three levels of radio education - inter-provincial, Dominion-Provincial and international. The fruits of such co-operation in educational broadcasting were programmes, such as "Young Canada Listens," "Kindergarten of the Air," "National Farm Radio Forum," "Sports College" and "National Citizen's Forum." The CBC emerged from the 1940's as a national clearing house for Canadian education. Through its radio broadcasts, publications, and co-operative relations with provincial and voluntary educational organizations, the Corporation helped to provide Canadians with a national educational experience. The CBC also provided the Canadian Government with a useful instrument in international radio education affairs. Radio's role in education also became firmly established in the 1940’s. Broadcasting functioned as an educational aid and was to be integrated into the traditional learning situation. No new methodology or philosophy accompanied the radio into the classroom. True to an early prophecy, the radio had expanded the range of possible experiences available to the learner, but that was where its educational influence terminated. / Education, Faculty of / Graduate

In the fall of 1986 the Galactic Radio Patrol began total power observations with the new seven feed system on the 91 metre radio telescope at Green Bank, W. Virginia. The data were taken at a wavelength of 6 cm, with Nyquist sampling intervals, in the region of the galactic plane corresponding to the coordinate ranges of 1=25 to 225 degrees, and |b| ≤ 5.5 degrees. Existing surveys at 6 cm provide a coverage of the galactic plane over the galactic longitude range 190 to 60 (through 360) degrees. This work is largely complementary in that its coverage is over the galactic longitude range of 25 to 225 degrees. A mapping technique has been developed to fully exploit this data. This technique will allow the mapping of the galactic region with a sensitivity several times that of previously available surveys and with reliable structural information on angular scales of ≤ 1 degree. The above technique was applied to a test region centred upon the supernova remnant G109.1-1.0. The resultant maps were compared to a previously published map of this supernova remnant in order to determine the strengths and reliability of the present reduction method. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

"When the subject of the use of FM radio in the public schools was suggested by the writer as a subject for a research paper one of the first comments made by a fellow student was, 'Radio is a dead issue. Television has already made it out of date.' This comment immediately made the subject a challenge. Had we in America, in less than a generation, advanced to rapidly that one of the world's greatest media of communication was already out of date? The writing of this paper is an effort to answer that question, and in answering it to present a picture of the status of frequency modulation broadcasting in the public schools throughout the nation today"--Introduction. / Typescript. / "August, 1953." / "Submitted to the Graduate Council of Florida State University in partial fulfillment of the requirements for the degree of Master of Arts." / Advisor: John W. Mitchell, Professor Directing Paper. / Includes bibliographical references (leaves 67-68).

No description available.

The purpose of this study is to determine what writers in the field consider essential information for a school administrator to have in inaugurating radio in the school.