1991 Fifth International Conference on HF Radio Systems and Techniques

22-25 July 1991

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Displaying Results 1 - 25 of 74
  • Fifth International Conference on HF Radio Systems and Techniques (Conf. Publ. No.339)

    Publication Year: 1991
    IEEE is not the copyright holder of this material | PDF file iconPDF (71 KB)
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  • Automatically controlled HF radio systems-towards standardisation

    Publication Year: 1991, Page(s):1 - 6
    Cited by:  Papers (2)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (413 KB)

    Automatic systems of three types are discussed: automatic channel selection (ACS), automatic link establishment (ALE), and automatically controlled radio systems (ACRS). Traffic analysis results are presented and discussed for different systems: ACC (asynchronous common channels), SCC (synchronous common channels) SSCT (synchronous separate calling/traffic channels) and ASCT (asynchronous separate... View full abstract»

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  • Simulation modelling of an adaptive HF network

    Publication Year: 1991, Page(s):7 - 11
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (356 KB)

    Describes the use of a computer simulation to model the performance of an adaptive HF radio network. Issues of simulation design, data gathering, validation and extension from small to large networks are considered.<<ETX>> View full abstract»

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  • Performed measurements on traffic capacity for adaptive HF systems

    Publication Year: 1991, Page(s):12 - 16
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (305 KB)

    Presents a method that can be used in order to measure the traffic capacity for adaptive HF systems in a net configuration. The method provides information about the net throughput and the time it takes for a message to be transferred between two stations in the net. Furthermore, it is shown how this method was applied on a test with four adaptive HF systems in order to obtain information about th... View full abstract»

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  • Artificial intelligence techniques in HF system design

    Publication Year: 1991, Page(s):17 - 20
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (248 KB)

    A number of adaptive communication systems have been designed which operate on 'traditional lines', i.e. using a procedural approach. The author discusses an alternative non-procedural approach exploiting knowledge-based techniques. This approach is applied to adaptive HF system design.<<ETX>> View full abstract»

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  • Results from on-the-air measurements with an adaptive HF radio system

    Publication Year: 1991, Page(s):21 - 25
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (357 KB)

    The performance of a modern HF radio communication system, Farcos (fast adaptive radio communication system) has been measured. The authors discuss the HF system design aspects and describe the test methods. Field trial data were statistically evaluated and diagrams are presented showing frequency availability and link set-up performance. The results of the on-the-air measurements confirm the qual... View full abstract»

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  • Design and evaluation of a variable-rate meteor-burst communication system

    Publication Year: 1991, Page(s):26 - 30
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (269 KB)

    Describes elements of a research programme aimed at obtaining greater reliability and throughput with meteor-burst communication (MBC) systems. Essentially, this is achieved by effectively adapting the instantaneous transmission rate in response to channel characteristics, rather than transmitting at a fixed rate, as with most previously deployed MBC systems. During several trials performed betwee... View full abstract»

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  • The effect of space diversity on a broadcast meteor burst system

    Publication Year: 1991, Page(s):31 - 34
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (337 KB)

    Presents preliminary results obtained from a simulated MB broadcast system implementing scanning diversity of signals received at two separated antennas. The results consider the optimum transmitted block size required for a broadcast MB system with and without the implementation of space diversity and a scanning combiner. The signal throughput enhancement achieved using a simple scanning diversit... View full abstract»

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  • A laboratory testbed for performance evaluation of adaptive HF systems

    Publication Year: 1991, Page(s):35 - 38
    Cited by:  Papers (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (288 KB)

    A laboratory testbed is described. Its inherent advantage of generating a full HF interference spectrum allows a direct connection of the antenna interface of the tested HF system to the testbed, without the need for baseband transformation. The interference spectrum is generated by DSPs, which makes it possible to offer identical conditions for each test.<<ETX>> View full abstract»

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  • A long range HF radio paging and response system

    Publication Year: 1991, Page(s):39 - 43
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (314 KB)

    The purpose of the system architecture of the HF message system is to reduce the power and complexity of the mobile stations. This has led to the use of geographical diversity. Results are presented which show the effectiveness of this technique although further work is required to obtain values of 'correlatedness' to compare with previous work. The use of a software modem means that the mobile te... View full abstract»

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  • Applied digital communications via HF radio

    Publication Year: 1991, Page(s):44 - 47
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (418 KB)

    Discusses a number of applications of microcomputers using automated transfers of messages between radio stations, mainly by means of packet radio techniques in the amateur radio environment. The world of amateur radio encompasses all the aspects of radio communications in a condensed form as the individual operator must know something about transmitters, receivers, antennas and propagation. The m... View full abstract»

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  • OTH radar receiving system design using synoptic HF environmental data base

    Publication Year: 1991, Page(s):48 - 53
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (371 KB)

    Estimates noise figure and dynamic range requirements for an Australian radar receiving system from the joint distribution of external noise and interference power. Two periods were selected for analysis, July 1986 and July 1990, to illustrate the joint behaviour with sunspot number.<<ETX>> View full abstract»

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  • Introducing correlation into two dimensional Monte Carlo simulations: an example for OTH radar

    Publication Year: 1991, Page(s):54 - 60
    Cited by:  Papers (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (440 KB)

    Most Monte Carlo simulations draw independent samples from statistical populations of random variables. For many applications, where strong correlation between samples is known or suspected, this traditional approach can lead to significant quantitative errors and can mask important physics. The author formally introduces correlation into two-dimensional simulations and gives a realistic and impor... View full abstract»

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  • A comparison between predicted and measured vessel cross-sections for ground wave radars

    Publication Year: 1991, Page(s):61 - 65
    Cited by:  Papers (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (335 KB)

    An experimental radar station has been developed by NORDCO Ltd. as well as an 'Advanced ground wave radar performance simulation' software. The simulation software has been extensively verified using data collected from the radar station. The authors report on the initial results obtained from an analytical model developed by NORDCO for evaluating the cross section of a vessel modelled as a parall... View full abstract»

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  • Recent results obtained using the Losquet Island HF sky-wave backscatter radar

    Publication Year: 1991, Page(s):66 - 69
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (258 KB)

    In order to study HF sky-wave propagation, an HF backscatter radar has been constructed by the French National Telecommunications Research Center (CNET) at Losquet Island near Lannion (Brittany). It has been operational since the beginning of 1990. this radar is used for evaluation of radiowave propagation and geophysical research. The authors present recent results in the following areas: real ti... View full abstract»

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  • HF skywave radar studies of ocean wave directional spectra near equilibrium

    Publication Year: 1991, Page(s):70 - 72
    Cited by:  Papers (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (245 KB)

    The author describes how the JINDALEE radar, together with a new wave directional spectrum estimation algorithm, is being used to study sea surface conditions near equilibrium. The angular spreading behaviour is of prime interest, since this attribute is poorly understood. Central to this investigation is the acquisition of sea clutter Doppler spectra over a range of radar frequencies spanning mor... View full abstract»

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  • Calculated and measured radiation characteristics of an HF loop antenna mounted upon a helicopter

    Publication Year: 1991, Page(s):73 - 78
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (511 KB)

    An HF loop antenna installation on a helicopter is described. The azimuthal radiation patterns at 10 frequencies throughout the HF band are obtained by three methods: mathematical modelling, measurements with a physical scale model, and measurements using the real aircraft in flight. The predictions from the mathematical model were made in advance of any measured results being obtained and no empi... View full abstract»

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  • Near vertical incidence skywave antenna examination

    Publication Year: 1991, Page(s):79 - 83
    Cited by:  Papers (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (349 KB)

    The US Marine Corps required near vertical incidence skywave mode antennas for mobile communication. Upon examination of potential antennas for the mobile application, short whip configurations using the standard whip, and loop antennas surfaced as the primary candidates to be examined. The authors briefly review the modeling efforts undertaken in the early phases of the study, followed by discuss... View full abstract»

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  • An assessment of the potential improvement in radiation efficiency of an aircraft HF antenna system using high temperature superconductors

    Publication Year: 1991, Page(s):84 - 88
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (420 KB)

    Estimates are made of the improvements which might be achieved to the efficiency of an aircraft HF antenna system at the bottom of the band by the use of high temperature superconductors (HTS). The particular system considered is that of a 'long-wire' antenna mounted upon a BAC1-11 aircraft. Because it is rather difficult to see how the antenna itself can be cooled to the required temperatures, at... View full abstract»

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  • Numerical design of shipboard communications antenna

    Publication Year: 1991, Page(s):89 - 92
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (165 KB)

    The shipboard communications antenna is sometimes realized as an L- or inverted T- configuration. The main electrical parameters which decide the usefulness of the antenna are: static capacity, effective length, and input impedance. The author looks at a computer aided design (CAD) system for shipboard communications antenna design on a personal computer. First, the structure and modelling techniq... View full abstract»

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  • Numerical modelling of the parasitic effects of supporting structures on HF Yagi arrays

    Publication Year: 1991, Page(s):93 - 96
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (201 KB)

    In many situations, both land-based and on various mobile platforms, HF antennas can be severely compromised by the parasitic coupling effects of conducting objects in their vicinity. The author describes the results of some modelling exercises on a typical HF array with nearby parasitic conductors using MININEC. The presence of unavoidable co-polarised conductors in the vicinity of an HF Yagi-Uda... View full abstract»

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  • HF null steering system with a wide-band structure

    Publication Year: 1991, Page(s):97 - 102
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (401 KB)

    Antenna array adaptive null-steering, which is a relatively new concept in HF offers the possibility of suppressing undesirable interferences, while preserving the desired signal. But good performance requires both special structures and high quality electronic circuits, especially for attenuators and phase shifters. It also requires a good mastering of parasitic delays and of impedance matching t... View full abstract»

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  • Near real-time information about the solar terrestrial environment and HF propagation with BTX

    Publication Year: 1991, Page(s):103 - 107
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (365 KB)

    HF propagation shows considerable day-to-day variation, caused mainly by the influence of variations in solar radiation. In order to maintain HF communications under changing propagation conditions it is necessary to adapt the frequencies in use to the real-time situation. Forecasts required for this purpose suffer from time lag between the observations of the propagation environment and the arriv... View full abstract»

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  • A review of methods for coping with ionospheric variability in connection with HF systems

    Publication Year: 1991, Page(s):108 - 112
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (560 KB)

    Ionospheric variability is one of the more fundamental problems encountered in the analysis of HF system performance, whether it be in the realm of hindcasting, nowcasting, or forecasting. In most instances the problem must be handled statistically. In some instances, typically in the arena of near-term forecasting, more deterministic approaches have been used. In general the approaches for coping... View full abstract»

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  • The research and development of a fully automated daily short-term ionospheric forecasting service

    Publication Year: 1991, Page(s):113 - 116
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (263 KB)

    A fully automated system producing short-term ionospheric forecasts has been developed at GEC-Marconi Research Centre (MRC). The computer algorithms use geophysical and radiowave propagation data available in the European sector. MRC produce a daily forecast of ionospheric and HF radiowave propagation conditions which is distributed to HF users. Customers receive the service via telex or facsimile... View full abstract»

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