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Broadcasting, IEEE Transactions on

Issue 2 • Date Jun 1988

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Displaying Results 1 - 25 of 28
  • Methodology and computer tools to semi-automate assessments of shortwave broadcast coverage resulting from multiple transmissions

    Publication Year: 1988 , Page(s): 283 - 291
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    A computer-assisted methodology, developed for using a point-to-point ionospheric propagation and communications system performance model to assess shortwave broadcast coverage, is presented. The listening area is approximated by a set of geographic coordinates (test points), and the required power gain (RPRG) for the link from each transmitter site to each test point is computed using the IONCAP ionospheric communications analysis and prediction program. The broadcasts may originate simultaneously from a single site or from multiple-transmitter sites (i.e., multicast). Figures of merit are assigned in terms of the RPG values, and area coverage statistics are computed for the simulated broadcasts. Three interactive computer programs were developed to permit a semi-automated multicast broadcast coverage analysis using IONCAP and a computerized equipment database. They are: propagation parameter set-up program; transmission plan set-up program; and multicast analysis program. View full abstract»

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  • Practical techniques for feeding two or more high power shortwave transmitters to one antenna

    Publication Year: 1988 , Page(s): 193 - 200
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (245 KB)  

    How multiplexers can be used in the shortwave frequency range for permitting two or three high-power shortwave transmitters to be connected to one curtain antenna array is described. Radio Free Europe/Radio Liberty Inc. (RFE/RL) has found that the use of multiplexers reduces the number of antennas required for a shortwave broadcast station. View full abstract»

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  • RELEDOP: a full-scale antenna pattern measurement system for high-powered HF transmitting antennas

    Publication Year: 1988 , Page(s): 210 - 220
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1052 KB)  

    A system is presented that utilizes a towed, 3-axis receiver called RELEDOP. RELEDOP is a receiving elementary dipole with optional polarization that measures the transmit directivity patterns of over-the-horizon backscatter (OTH-B) radars and shortwave broadcast transmitting arrays. A dielectric tow cable and a fiber-optic link to the towing aircraft permit excellent electromagnetic isolation of the RELEDOP sensor from the aircraft. High accuracy in position location (±15 m in x, y, and z) and fast-receiver sampling permit orthogonal polarization component measurements with accuracies of ±0.15° in bearing and ±1 dB in relative amplitude. Calibrated receiving element gains permit measurement of absolute field strength. The field strength data, combined with the position data, permit an assessment of transmitter effective radiated power (ERP); a knowledge of input power permits a computation of absolute gain of the transmitting antenna to ±3 dB or better. The RELEDOP system is described, along with its subsystems; towed sensor, airborne, positioning, ground station, and communications subsystems. Example patterns and flight path tracks illustrate the output graphics View full abstract»

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  • A double-sideband shortwave-broadcast signal-quality estimation algorithm

    Publication Year: 1988 , Page(s): 263 - 282
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1252 KB)  

    A method and related algorithm for assessing the quality of a full-carrier, double-sideband signal are presented that were developed through statistical processing of empirical measurements of parameters of the received signal before and after detection. Preliminary results are presented showing the comparison of the objective automated measurement ratings against subjective human listener ratings of overall quality on a five-level scale. The algorithm has been developed to gauge the perceived quality and, inferentially, the intelligibility of a broadcast composed of speech, given that the ultimate goal of a broadcaster is to have the message received and understood by the largest audience possible. The algorithmic measures apply to all broadcast program material; music, as well as speech View full abstract»

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  • HE receiving antenna directivity patterns and gain for ionospheric propagation model predictions for shortwave broadcasting

    Publication Year: 1988 , Page(s): 221 - 229
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Elevation-plane relative directivity patterns of a 9-ft rod measured with the XELEDOP full-scale HF antenna pattern measurement system are compared with values assumed by the Voice of America (VOA) and the British Broadcasting Corporation (BBC). Values of such directivity patterns and gain for a 7.5-ft monopole with sixteen buried ground radials, measured at the same site, are compared with predictions of directivity and gain made with the numerical electromagnetics code (NEC). An extensive set of recommendations is offered, regarding the appropriate assumptions for the receiving antenna in ionospheric propagation prediction programs View full abstract»

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  • The early history of US international broadcasting from the start of World War II

    Publication Year: 1988 , Page(s): 82 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    At the time the US entered into world War II in 1941, there were eleven shortwave international broadcasting stations in the US, all privately owned by companies or foundations. Recognizing the psychological warfare potential of these facilities, the US Office of War Information (OWI), an agency under the Executive Office of the President, negotiated operating contracts with the owners and established studios in New York and San Francisco to provide government programming. This was the origination of the Voice of America. At the same time, budget requests were made to the US Congress and funds appropriated for shortwave facilities expansion and for certain overseas stations operated by the overseas branch of the OWI. The operational and expansion programs which increased the number of shortwave transmitters to 36 in eight station sites by the end of World War II are reviewed. At the end of the war, the OWI was replaced by the US Information Agency (USIA) with its international broadcast service operating the Voice of America. The further expansion of shortwave broadcasting under USIA is outlined View full abstract»

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  • High frequency propagation losses on an open wire transmission line above dissipative Earth

    Publication Year: 1988 , Page(s): 292 - 300
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    Both exact and simplified approximate equations for the current on a pair of conductors above a dissipative Earth are developed. Since, in many practical cases, each conductor consists of a pair of wires, a method for reducing four-wire lines to equivalent two-wire lines is presented. The assumptions used in the approximate expression are that the cross-sectional dimensions of the line (e.g. the distances between conductors but not the height of the conductors above earth) are small compared to the wavelength, that the propagation constant in the Earth is larger than the one in air, and that the conductors are thin compared to the wavelength and any cross-sectional dimension. The first assumption restricts the validity of the equations for the current to below 100 MHz (λ=3 m) for typical transmission lines and the second assumption can be met for most practical air-Earth problems. Numerical results for transmission line loss are computed using both the approximate method and the exact method. It is seen that the two results agree well for frequencies less that 100 MHz. The loss is divided into conductor loss and Earth loss and plotted, and physical interpretation of the frequency dependence of each component is given. The results of a parametric study of transmission-line loss are given along with an interpretation View full abstract»

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  • Shortwave broadcasting band spectrum occupancy and signal levels in the continental United States and Western Europe

    Publication Year: 1988 , Page(s): 115 - 125
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (944 KB)  

    The initial results are described for monitoring using a mobile spectrum monitoring unit (MSMU) that has the capability of fast sampling of radio signals in the frequency spectrum between 2 MHz and 1 GHz. In the summer and autumn of 1987, the MSMU was used to measure signal level and spectrum occupancy in the shortwave band (2-30 MHz) at four locations in the continental United States (CONUS) (i.e. Stanford, California; Ft. Huachuca, Arizona; Ft. Sill, Oklahoma; and Annapolis, Maryland) and at two locations in Europe (Seckenheim and Geinsheim, Federal Republic of Germany). After the measurement period, the recorded data was used to compute occupancy statistics at 111 signal amplitude thresholds. Comparison of spectrum-occupancy and signal-level data between CONUS and Europe is reported View full abstract»

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  • Collocation of receivers and high-power broadcast transmitters

    Publication Year: 1988 , Page(s): 154 - 158
    Cited by:  Papers (13)  |  Patents (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    Receiving antennas and receivers can be collocated with the transmitting antennas and transmitters, if appropriate interference suppression is effected. Since the time-varying characteristics of the interference from adjacent transmitters may not be known a priori, and since the propagation path characteristics may change with time, interference needs to be suppressed by adaptive means. Operational characteristics of the adaptive control system in a shortwave broadcast station and expected degree of cancellation of the unwanted interference are discussed. Some recent tests to evaluate the effectiveness of the adaptive control in the relay station of Voice of America at Delano, California are outlined. Both laboratory and field tests show that adaptive interference-suppression systems can be designed and built for real-life environments expected in broadcast and relay stations View full abstract»

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  • An improved high efficiency 500 kilowatt short wave broadcast transmitter with novel features

    Publication Year: 1988 , Page(s): 134 - 136
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    Some of the changes in international broadcaster's HF (high-frequency) transmitter needs are addressed, along with some adaptations in HF transmitter design to reflect those needs. The authors identify three fundamental changes in the emphasis of international broadcast transmitter requirements: due to increasing energy costs, more emphasis has been placed on equipment power efficiency; due to increasing labor costs, more attention is being paid to automation and ease of maintenance, i.e. manpower efficiency; and, third, because of spectrum crowding, improved spectral occupancy has become a concern, particularly with respect to transmitted signal purity, and spectral-efficient modulation modes. Several developments designed to meet these needs of broadcasters are described. The issue of power efficiency has been met with improved transmitter RF and modulator circuits. RF efficiency has been improved in part by lowering losses in RF output coupling circuits. This improvement is afforded by better network design, and better automatic tuning, i.e. tuning for best efficiency. More efficient RF output tubes have also been developed View full abstract»

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  • The renaissance of privately-licensed shortwave broadcast stations in the United States

    Publication Year: 1988 , Page(s): 87 - 93
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    The status of privately licensed shortwave broadcast stations in the US is reviewed. The stations are identified, and their reasons for broadcasting are examined. The laws, rules, and regulations which permit these stations to operate in a world of government-funded stations are discussed, along with the technical standards that they are required to meet, and the particular technical problems that they face View full abstract»

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  • High performance antenna systems for new VOA stations

    Publication Year: 1988 , Page(s): 167 - 179
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    Advancements in curtain-type high-frequency (HF) broadcast antennas are reviewed. Novel high-performance antennas for the Voice of America (VOA) are described, including vertical and horizontal beam selections, performance measurements, effects of finite ground and hills, radiation hazard zones, and transmission lines. Specifications for antennas to be installed at four new VOA stations are examined. The designs provide substantial flexibility in radiation-beam characteristics with four vertical beam modes and seven horizontal beam angles. it is believed that the technique of selecting the optimum radiation beam for ionospheric propagation to VOA target areas will provide a substantial improvement in the performance View full abstract»

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  • The merits of modern technology for today's high power short-wave transmitters

    Publication Year: 1988 , Page(s): 126 - 133
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    Developments in high-power shortwave transmitters are described, and practical experience with such transmitters is reported. Topics discussed are: high-level anode modulation, the pulse step modulator (PSM), the switching module, control of the PSM, the RF driver and final stage, and other modulation techniques View full abstract»

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  • Interference-reducing antennas for shortwave broadcast listeners

    Publication Year: 1988 , Page(s): 159 - 166
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (880 KB)  

    Principles useful in the design of directional antennas capable of reducing interference in shortwave-broadcast reception are identified. Examples are given of designs which go beyond the time-honored vertical loop. It has been found that significantly improved rejection of both ground- and sky-wave interference can be obtained with minimum modification to the associated receiver, even in typical indoor environments. Measurements suggest that single-source sky-wave signal reductions of 20 dB can be achieved on average. This is sufficient in many instances to give satisfactory separation of two signals on the same frequency of comparable strength and having azimuth differences of 90° or greater. It seems likely that widespread use of these antennas would significantly reduce the severity of co-channel interference in shortwave broadcasting View full abstract»

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  • Shortwave propagation prediction methodologies

    Publication Year: 1988 , Page(s): 230 - 237
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    The status of ionospheric-propagation prediction models is examined, with particular emphasis on the use of these models by the shortwave-broadcast community. Their stand-alone capability for forecasts is found to be limited by the use of monthly median, statistical averages of archived ionospheric data, as well as by the use of imprecise control parameter inputs, such as the sunspot number. A variety of developing technologies are discussed for improvement of prediction models. Improvement may result from observations of coronal holes and other relevant solar features for long-term and short-term ionospheric predictions. Also discussed are a variety of other ionospheric measurement schemes for short-term ionospheric predictions, such as the use of vertical-incidence, oblique-incidence, and backscatter sensing from space. The application of this class of measurements for adaptive HF broadcasting systems is discussed. Incorporation of ray-tracing into propagation calculations in the prediction model is also considered View full abstract»

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  • A methodology for modeling the reliability, availability and maintainability (RAM) of a generic shortwave broadcast relay station

    Publication Year: 1988 , Page(s): 242 - 262
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1480 KB)  

    A methodology for developing a reliability, availability and maintainability (RAM) model that is applicable to evaluating conceptual designs for shortwave broadcast relay stations is described. A generic relay station (GRS) that has nine major subsystems exclusive of ionospheric propagation path is proposed. The reliability of the propagation path to the listeners is not addressed. An example of the use of the methodology is presented for the GRS and the sensitivity of the model results is studied for the most significant subsystems from a RAM standpoint: the satellite earth station that delivers the program feeds and the high-powered transmitters View full abstract»

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  • Computer control and monitoring of the 420B-1 500 kW HF transmitter

    Publication Year: 1988 , Page(s): 137 - 140
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    The principal design features of the computer portion of the 420B-1 high-frequency transmitter are discussed, both from a hardware and a software standpoint. The point is made that the primary task of the computer is to simplify operation of the transmitter. Although the computer is an integral part of the control circuit, the transmitter can operate without the computer View full abstract»

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  • The results of WARC-HFBC (87): technical implications

    Publication Year: 1988 , Page(s): 102 - 108
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    The planning principles and technical parameters that were decided at the 1987 second session of the World Administrative Radio Conference (WARC) for the planning of the HF bands allocated to the broadcasting service (HFBC) are described. These planning principles and parameters are intended for use in developing test plans to satisfy the world's high-frequency broadcast requirements. Those parameters that were modified at the second session of the conference are discussed toward obtaining a workable and universally acceptable planning system for shortwave broadcasting. With reference to the results of the planning exercises that were used as the basis of decisions at the second session, the likely impact of these decisions on the HF broadcast planning process is described. Some issues that are likely to concern the US broadcasters in preparation for the third session of WARC are summarized in conclusion View full abstract»

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  • The evaluation of 500 kW shortwave transmitters at the Voice of America

    Publication Year: 1988 , Page(s): 147 - 153
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    The Voice of America (VOA) has initiated a major program to modernize and expand its worldwide broadcast system. The program includes the procurement of 500-kW shortwave transmitters both for new stations and as replacements for aging and less efficient equipment in existing facilities. To develop and verify a specification for new transmitters, four currently available 500-kW transmitters were purchased from separate vendors for evaluation at the VOA facility in Greenville, North Carolina. The intent of this off-the-shelf approach was to ensure a proper level of technical rigor in the specification without unduly restricting competition among suppliers. The evaluation focused on a variety of factors including installation, performance, operability, and maintainability. The procedures followed during the evaluation are described and some of the salient findings are presented View full abstract»

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  • High-power, broad-bandwidth HF dipole curtain array with extensive vertical and azimuthal beam control

    Publication Year: 1988 , Page(s): 201 - 209
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    The design, construction details, and performance of a prototype high-power HRS 12/6/.5 antenna system covering the 6 to 26 MHz international broadcast bands are presented. The antenna has been developed, erected, and tested as part of the Voice of America modernization program to demonstrate the feasibility of controlling the horizontal and vertical apertures and beam directions of high-power, broad-bandwidth (2:1 frequency ratio) antennas. The antenna system provides 11 vertical slews, 15 azimuthal slews, and five azimuthal widths. The peak of the elevation pattern can be steered to angles of 4° to 20° above the horizon and the azimuthal beam can be steered up to ±30° with respect to boresight. Gains range from 16 to 31 dBi. Azimuthal beamwidths between -6 dB points range from 8° to 75°. The antenna is designed to handle the input power of one or more 500-kW double-sideband, amplitude-modulated transmitters. The antenna system has been designed using basic dipole and antenna switching modules from which smaller subarrays (HRS 2/6/.5, HRS 4/6/.5, HRS 8/6/.5, etc.) can be readily developed. The extensive beam control provided by the antenna system enables a shortwave broadcaster to use fewer antennas to reach the same audience. This reduces the land area of the station as well as its acquisition and operating costs View full abstract»

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  • The Wertachtal shortwave broadcasting station

    Publication Year: 1988 , Page(s): 306 - 308
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    A description of the Wertachtal, West Germany shortwave broadcasting station is presented, along with modifications to satisfy Voice of America (VOA) requirements. A brief description of proposed high-efficiency transmitters, and new computers and supervisory equipment is included View full abstract»

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  • Jamming to the HF broadcasting service

    Publication Year: 1988 , Page(s): 109 - 114
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The Institute for Telecommunication Sciences has been actively involved in an internationally coordinated monitoring program to determine the location of emitters of harmful interference (jamming) to the high-frequency (HF) broadcast service. four monitoring programs were undertaken between October 1984 and June 1986. The procedures that have been used and the results that have been obtained are summarized. The locations of the emitters that cause jamming to the HF broadcast service are shown and selected characteristics of the jamming environment are described. The degree to which jamming that is directed to certain broadcasters adversely impacts the performance of other broadcast services that operate on the same or adjacent channels as the targeted broadcaster is examined View full abstract»

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  • The future of high frequency broadcasting

    Publication Year: 1988 , Page(s): 94 - 101
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    Since the end of World War II, the number of daily frequency hours used by high-frequency (HF) broadcasting (also known as shortwave and band 7, 3-30 MHz) has tripled. Approximately 35000 daily frequency hours are carried in an HF spectrum that can barely accommodate half that amount. As a consequence, congestion is severe, and interference levels intolerably high. Attempts to remedy this situation by planning the high-frequency bands date back to 1947, but, thus far, they have not been successful. International planning conferences in 1984 and 1987 have shown a possibility for agreement; another conference is tentatively scheduled for 1992. Some broadcasters have attempted to solve their congestion problems by moving out-of-band, sometimes expanding their services int bands allocated to other services, such as amateur radio, fixed, aeronautical, and mobile. It is feared this trend will continue. The attempts that have been made to plan the HF bands in an effort to alleviate congestion are described and the outlook for the remainder of the 20th century is discussed View full abstract»

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  • High frequency sky-wave propagation predictions in the design of broadcast systems

    Publication Year: 1988 , Page(s): 238 - 241
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    Classical methods used to predict the performance of point-to-point sky-wave systems are extended to the design of high-frequency broadcast systems through a summarizing procedure based on the use of time-location samples. Examples of frequency, antenna, and site selection are shown. It is concluded that predictions of these types are most useful when comparisons are involved; e.g. selection of antennas, and choice of sites View full abstract»

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  • High-power steerable short-wave antennas

    Publication Year: 1988 , Page(s): 186 - 192
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    The theoretical study and model measurements on a high-power, steerable shortwave antenna covers a spherical reflector, a parabolic reflector, and a log-periodic switch-steerable-type antenna. The scale modeling facilities are described and the modeling results are presented. The spherical reflector gives reasonable good azimuth and elevation steering over the shortwave band from 5.8 MHz to 27 MHz. The parabolic reflector gives good azimuth steering, with higher gain but no vertical steering. The log periodic antenna provides a high-gain switch-steerable antenna suitable for over-the-horizon radar detection View full abstract»

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IEEE Transactions on Broadcasting covers the field of broadcast technology, including the production, distribution, transmission, and propagation aspects of broadcasting.

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