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BBC Research and Development Reports

A collection of BBC Research and Development reports and white papers, dating from the 1960s through to 1996.



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R&D Report 1990-15 : The design and application of modular, acoustic diffusing elements. R. Walker The requirements for and the advantages of a modular acoustic diffusing element are described. This module was intended to complement the existing range of acoustic absorbing elements already in widespread use. The theoretical background to the principles is summarised, based on the published work of M.R. Schroeder, and a design for such a module is discussed. The performance of the resulting...
Topics: acoustic, diffusers, bbc, primitive, frequency, modular, diffusing, sequence, module, diffuser,...
R&D Report 1954-26 : The subjective discrimination of pitch and amplitude fluctuations in recording systems A.E. Axon, A. Stott. The present report is largely concerned with the subjective aspects of wow and flutter and describes work carried out to determine the sensitivity of the listener to these pitch fluctuations.
Topics: modulation, frequency, amplitude, flutter, frequencies, subjective, fluctuations, threshold,...
R&D Report 1977-19 : Film lighting using metal-halide lamps: some operating conditions giving freedom from picture luminance fluctuations. E.W. Taylor Film and display parameters required to specify the operating conditions and describe exposure variation and luminance fluctuation effects are defined. Theoretical relationships between camera frame frequency and shutter angle, and lamp supply frequency and intensity ripple characteristics, such that picture luminance fluctuations due to the...
Topics: ripple, frequency, asymmetry, luminance, exposure, supply, camera, lamp, fluctuation, charts,...
R&D Report 1983-08 : The improved display of 625-line television pictures. A. Roberts Conventional television, shown on the 625/50 standard with 2:1 interlacing of adjacent fields suffers several minor defects which become much more visible on large, bright displays. Large-area flicker and interline (interlace) twitter are easily seen, and line crawl, resulting from interlace, occasionally causes the picture to appear to be composed of only 312.5 lines. All these effects can be eliminated...
Topics: twitter, structure, picture, algorithm, display, interlaced, vertical, scanning, motion, crawl,...
R&D Report 1956-03 : The Ronette crystal microphone cartridge Type MC.65. W.I. Manson, D.E.L. Shorter The report gives tests results on three samples of the Ronette diaphragm-type crystal microphone cartridge MC.65. The performance varies considerably between individual specimens but is on the average superior to that of earlier microphone of this kind.
Topics: microphone, ronette, frequency, crystal, cartridge, specimens, response, specimen, axial, noise,...
R&D Report 1975-04 : Digital video: Sub-Nyquist sampling of PAL colour signals. V.G. Devereux A simple method of applying sub-Nyquist sampling techniques to digital coding of PAL colour video signals is described. This technique employs a sampling frequency of twice the colour subcarrier frequency, the sampling instants being maintained at a specified phase relative to the reference subcarrier. For System I (625-line, PAL) video signals the resulting sampling frequency is about 8.87 MHz....
Topics: sampling, frequency, signal, components, filter, signals, comb, pal, video, subcarrier, pal video,...
R&D Report 1962-45 : 405-line and 625-line television pictures: The relative impairment produced by random noise. W.K.E. Geddes Subjective assessments have been made, for 405-line and 625-line television pictures, of the impairment produced by addition of random noise to the video signal. It has been found that, for equal impairment, the signal-to-noise ratio must be about 2 dB for a 405 line picture for a 625-line picture.
Topics: noise, subjective, bandwidth, impairment, ratio, random, attenuator, triangular, flat, television,...
R&D Report 1976-12 : Audio non-linearity: A comb-filter method for measuring distortion. R.A. Belcher A new method of measuring non-linear distortion of sound signals is described. This method uses a test-noise signal, based on a pseudo-random sequence and occupying most of the audio band, in conjunction with comb-filter techniques to measure distortion over a wide frequency range; it gives better correlation with subjective test results than the conventional total harmonic distortion...
Topics: distortion, test, signal, subjective, harmonic, impairment, frequency, method, circuits,...
R&D Report 1967-18 : The use of flexible couplings to reduce the transmission of vibrations through water pipes D.K. Jones In studio centres now being built in which a combination of hot-water radiators and simple ventilation systems is used instead of complete air conditioning, vibrations transmitted along the hot-water pipe system into the studios may constitute a source of acoustic noise. This report describes a series of experiments which were undertaken to determine the reduction in...
Topics: couplings, coupling, flexible, transverse, pipe, radiated, vibration, pipes, transmission,...
R&D Report 1966-31 : Colour film and colour television C.B.B. Wood This report discusses the use of colour film for colour television, with particular reference to the choice of film stocks.
Topics: colour, film, television, mhz, eastman, kodachrome, telerecording, films, ektachrome, contrast,...
R&D Report 1995-03 : Controlled Image Design: The measurement of Time-Frequency responses. R. Walker This Report describes the measurement of acoustic events in a 3-dimensional measurement domain. An outline of the general theoretical background is followed by a description of the special requirements for the measurement of short-term acoustic responses in rooms. The results of measurements on an experimental synthesis of a single room reflection are also presented. It is shown that the...
Topics: frequency, response, fourier, measurement, transform, impulse, reflection, signal, responses,...
R&D Report 1994-12 : A wideband absorber for television studios. M.D.M. Baird The acoustic treatment in BBC television studios has taken various forms to date, all of which have been relatively expensive, some of which provide inadequate absorption. An investigation has been conducted into the possibilities of producing a new type of wideband absorber which, would be more economic, also taking installation time into account, than earlier designs. This Report describes the absorption...
Topics: absorption, absorber, wideband, frequency, acoustic, mineral, bbc, zintec, weldmesh, absorbers,...
R&D Report 1973-35 : Visibility of chrominance/luminance delay inequality in System I (625-line PAL) video signals V.G. Devereux, G.C. Wilkinson An investigation, including subjective tests, has been carried out concerning the visibility of chrominance/luminance delay inequalities in System I (625-line PAL) video signals. The results obtained indicate that the threshold of visibility of this type of picture impairment corresponds to a delay inequality of about +/- 50ns on critical pictures...
Topics: delay, inequality, luminance, tests, subjective, grade, chrominance, impairment, lessman, timing,...
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R&D Report 1954-23 : The Neumann microphone Type U47 H.D. Harwood, R.J. Packer A new directional electrostatic microphone, type U 47, produced by the firm of Neumann in Berlin, incorporates the capsule originally designed for the type M 49 microphone but uses a cheaper form of head amplifier. The U 47 microphone is designed to give either cardioid or omnidirectional polar response. Frequency characteristics, sensitivity and noise have been measured on a single specimen for both conditions....
Topics: microphone, omnidirectional, cardioid, characteristics, condition, output, neumann, frequency,...
R&D Report 1988-14 : On the design of loudspeakers for broadcast monitoring. C.D. Mathers By designing its own monitoring loudspeakers for about the past forty years, the BBC has achieved a degree of continuity and consensus in a subject where there are almost as many opinions as there are designers. This report describes the approach that has evolved within the Corporation towards design and assessment, and indicates how calculation and objective measurement are supplemented by experience...
Topics: loudspeaker, bbc, design, frequency, damping, coil, acoustic, unit, diaphragm, drive, relative...
R&D Report 1954-04 : Some problems influencing the design of a machine for the high-speed dubbing of magnetic recordings. P.E. Axon The purpose of this report is to give an appreciation of some of the problems which will be met with in an alternative approach to tape duplication by the process of high-speed multi-tape dubbing.
Topics: tape, recording, dubbing, spool, reproducing, tension, shaft, magnetic, required, frequencies,...
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R&D Report 1955-33 : Vertically polarised Band III aerial for Crystal Palace. P. Knight, G.D. Monteath, G.J. Phillips This report describes the first stage in the development, using a small-scale model, of a vertically-polarised aerial for radiating two television programmes in Band III from the Crystal Palace television station. The aerial consists of 8 tiers of tangential batwing elements mounted on a 4 ft 4 in. (1.32 m) square section of the tower.
Topics: admittance, aerial, elements, iii, tiers, mast, feeder, batwing, tier, element, mutual admittance,...
R&D Report 1956-23 : Compatibility of the NTSC colour television system adapted to the 405-line standard: Field trials. W.N. Sproson Three series of field trials have been undertaken to test the compatibility aspect of the adapted N.T.S.C. colour television system.
Topics: chrominance, picture, observers, grades, grading, tests, questionnaires, slides, dots,...
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R&D Report 1959-10 : Peterborough: Television and V.H.F. sound services; Site tests. D.W. Taplin, C.J. White, R.S. Sandell, J. Hall The results of a site test at Morborne Hill, near Peterborough, are given. A Band I transmitter with a mean effective radiated power (e.r.p.) of 1.1 kW will provide a much improved service over most of the area but the overlap with the adjacent Crystal Palace and Holme Moss transmitters is inadequate in certain areas. A Band II transmitter with a mean e.r.p. of...
Topics: transmitter, peterborough, strength, television, unipoles, exceeded, contours, field, field...
R&D Report 1957-10 : Some experiments on the subjective effect of limiting the upper frequency range of programmes D.E.L. Shorter, W.I. Manson, E.R. Wigan To obtain first-hand knowledge of the subjective effects of high-frequency band limitation, some tests have been carried out with Research Department staff of various categories as observers (thirty-four in all), using twelve types or recorded programme material. Low-pass filters having nominal cut-off frequencies of 10 kc/s and 12 kc/s...
Topics: observers, filter, frequency, observer, programme, experiments, filters, band, material,...
R&D Report 1959-08 : Low-signal amplifying valves for use at U.H.F. R.G. Manton The object of this report is to review some of the types of valve that are suitable for use in u.h.f. amplifying stages in receivers, and to describe units which have been constructed to test the performance of two of these valves at a frequency of about 655 Mc/s.
Topics: amplifier, valve, output, input, amplifiers, anode, bandwidth, grid, gain, impedance, electrical...
R&D Report 1961-07 : Crystal-diode modulators for the frequency range 10-1000 Mc/s. G.J. Phillips, R.G. Manton This report describes the development of low-power balanced diode modulators suitable for amplitude modulation by television or sound signals of a carrier in the frequency range 10-1000 Mc/s. From an original model, built in 1954, two later models have been developed having better performance in regard to the insertion loss at the carrier frequency, and uniformity of modulation...
Topics: modulator, modulation, frequency, insertion, signal, amplitude, impedance, transformer, output,...
R&D Report 1963-27 : An introduction to the theory of aerials H. Page This report gives an introduction to the theory of aerials with emphasis on broadcasting. The function of an aerial, when transmitting, is to propagate the electro-magnetic waves flowing from the source into space.
Topics: aerial, radiation, impedance, vertical, doublet, field, aerials, current, transmitting, pattern,...
R&D Report 1963-14 : Television co-channel interference: Some effects of the modulation of the interfering signal. E.W. Taylor The configuration of the interference pattern produced when a television transmission suffers co-channel interference from another television signal is examined in detail, in order to determine the process by which the interfering modulation gives rise to additional patterns. The description of these patterns in terms of the carriers and side-bands of the two...
Topics: interfering, frequency, pattern, signal, wanted, sideband, subsidiary, sidebands, principal,...
R&D Report 1966-06 : Subjective assessments of the portrayal of motion produced by simulations of field-store standards conversion R.E. Davies, S.J. Lent, M.T.A. Salter It is shown that the process of television standards conversion involving a change of field frequency degrades the portrayal of movement in the scene by introducing a jerky motion to certain types of movement. Experiments are described which show that in order to provide satisfactory portrayal of motion, when converting...
Topics: frames, fields, movement, conversion, standards, portrayal, observers, second, grade, picture,...
R&D Report 1967-03 : Field-store standards conversion: a controlled RF switch G.M. Le Courteur This report describes the development of a type of rf switch unit which is intended to control the rf signal routing in an experimental field-store standards converter. The switches are actuated by uni-directional control signals and contain built-in amplification so that they can be adjusted to have zero loss.
Topics: switching, switch, signal, impedance, input, element, diode, output, unwanted, switches, unwanted...
R&D Report 1966-51 : UHF transmitting aerial for Black Hill television station G.H. Millard A u.h.f. transmitting aerial for the Lanarkshire area has been built on the support column of the existing ITA mast at Black Hill. The aerial came into operation with trade transmissions on 11th June 1966 and started full service on 9th July 1966.
Topics: aerial, channel, feeder, transmitter, mast, vision, radiation, horizontal, bbc, arrangement,...
R&D Report 1968-05 : Kilvey Hill UHF relay station: Summary of installation A.H. Jones Brief data sheet detailing equipment used, frequencies, radiation characteristics etc, together with graphs of horizontal and vertical radiation patterns.
Topics: kilvey, vertical, radiation, transmitter, power, horizontal, relay, hill, technological,...
R&D Report 1967-51 : Diurnal and seasonal variations in tropospheric propagation characteristics C.P. Bell In the channel sharing problems associated with broadcast planning at VHF and UHF it is usually assumed that interference from co-channel stations occurs randomly in time. This implies that there is equal probability of occurrence of the meteorological conditions giving rise to abnormal tropospheric propagation at any time of day or any season of the year. In this report the results of...
Topics: propagation, paths, field, strength, ctn, seasonal, diurnal, exceeded, transmission, tropospheric,...
R&D Report 1970-22 : Television reception over sea paths: The effect of the tide P.A. Levan, D.W. Taplin, C.P. Bell On oversea paths within the horizon, the received field strength is the vector sum of a direct component and a component reflected from the surface of the sea. If the level of the sea varies, the relative phase of the reflected component alters and causes field strength variations. To determine the effect of these variations on UHF television reception, a series of...
Topics: fading, aerial, field, strength, receiving, reflection, path, vertical, tidal, variations, path...
R&D Report 1971-34 : Channel 21 television transmissions: Interference to services below 470 MHz R.V. Harvey Some types of communication equipment that are used by public services at frequencies in the private mobile radio band operate just below 470 MHz. The results are given of laboratory tests to determine the susceptibility of this equipment to interference from lower-sideband radiation from Channel 21 television transmitters. The operational factors affecting the incidence of...
Topics: interference, mhz, khz, frequency, sideband, channel, transmitter, receiver, television, signal,...
R&D Report 1971-45 : A colour television illuminant consistency index W.N. Sproson, E.W. Taylor A proposal is put forward for a quantitative method of assessing the suitability of lamps as sources of illumination in colour television broadcasting.
Topics: colour, illuminant, test, bbc, camera, values, consistency, reference, reflectance, colours, skin...
R&D Report 1973-17 : MF propagation: Non-reciprocal ionospheric propagation on multi-hop paths P. Knight At medium frequencies, polarisation coupling loss occurs on multi-hop paths when waves reflected from the Earth's surface re-enter the ionosphere. Under some circumstances the coupling loss changes significantly when the direction of propagation is reversed.
Topics: polarisation, propagation, wave, paths, reflection, bbc, reflected, loss, brewster, mhz, dip...
R&D Report 1976-20 : An experimental 4-phase differential-phase-shift-keying system to carry two high-quality digital sound signals. M.J. Kallaway The report describes an experimental 4-phase differential-phase-shift- keying system to carry two high-quality sound signals. The system has possible applications in outside broadcast links and satellite broadcasting. The system offers a good compromise between the requirements of carrier power, signal bandwidth and instrumental simplicity. The...
Topics: signal, carrier, phase, amplitude, modem, spectrum, recovery, digital, symbol, experimental,...
R&D Report 1979-24 : A statistical analyser for digital field strength data. A.P. Robinson This report describes digital equipment using a microprocessor which carries out a statistical analysis of field strength data as measurements are made. The results are obtained immediately and are printed. The analyser is intended primarily for use with a measuring receiver in a vehicle but the report also discusses the scope for other applications. The equipment obtains results which used to be...
Topics: analyser, marker, event, samples, data, markers, field, strength, median, block, digital field,...
C.D. Mathers, K.F.L. Lansdowne Exposure to high sound levels can cause damage to the auditory system, either gradually over a period of time, or, in the case of very intense sounds, instantaneously. Particular care is therefore required in the use of headphones, which are capable of generating much higher effective sound levels than loudspeakers. This report summarises the results of a series of tests which show that headphone wearers tend to listen at significantly higher levels than...
Topics: headphone, hearing, levels, headphones, tests, artificial, ear, sound, loudspeakers, listening,...
R&D Report 1979-27 : Synchronisation of the Radio-4 (UK) transmitter chain on 200 kHz. G.H. Millard, R.D.C. Thoday, H.M. Price The means by which the carriers of three high-power broadcast transmitters operating at a frequency of 200 kHz are phase locked are described and the effect on the service is assessed.
Topics: phase, khz, frequency, aerial, westerglen, transmitters, transmitter, signal, droitwich, pontop,...
R&D Report 1988-04 : Television animation store: control system operation and implementation. D.G. Kirby This Report describes the computer control system of the electronic rostrum camera animation system developed to enable picture sequences to be generated directly as television signals, instead of using cine film. The ergonomics of the control system are described, together with some of the more demanding aspects of its implementation, which allow complex animated sequences to be...
Topics: animation, disc, sequence, pictures, video, picture, data, control, storage, system, data entry,...
R&D Report 1987-19 : Designing variable-length codes with good error-recovery properties. M.J. Knee An algorithm for calculating the expected resynchronisation time of a variable-length code following a transmission error is described. The results of calculations based on examples are used, together with insights gained from a simplification of the algorithm, to determine the effect on the expected resynchronization time certain easily recognizable design features of codes. The report...
Topics: code, error, codes, codewords, resynchronization, probability, algorithm, codeword, sequence,...
R&D Report 1996-07 : EUREKA 147: Subjective assessment of the error performance of the DAB system, including tests at 24 kHz audio sampling frequency. M. Lever (CCETT), J. Richard (CCET), N.H.C. Gilchrist This Report describes tests carried out by the authors and other members of Eureka 147 Working Group âAâ, to assess the performance of the DAB (Digital Audio Broadcasting) system with a low carrier-to-noise ratio at the receiver. The tests were conducted using a number of listeners to...
Topics: uep, mono, stereo, joint, audio, tests, rayleigh, eep, onset, impairment, bit rate, rural rayleigh,...
R&D Report 1960-03 : The power gain of multi-tiered VHF transmitters aerials P. Knight, G.D. Monteath Transmitting aerials for vhf broadcasting usually consist of a number of similar groups or tiers of radiating elements, spaced at intervals along a supporting mast. The power gain of such an arrangement depends on the number of tiers, on the spacing between them, and also on the vertical radiation pattern of each individual tier. A method of calculating the gain is described in this report....
Topics: ooooo, ooo, oooooo, mmmmm, oooo, cfl, iiiii, gain, ooooo ooooo, tfl, moooo ooooo, power radiated,...
R&D Report 1976-34 : A wide-deviation FM receiver. D.E. Susans The report describes two, simple, wide-deviation FM receivers, one operating in the frequency range 40 MHz to 50 MHz, the other in the range 88 MHz to 100 MHz. The receivers are intended for use with an FM system similar to that of the existing VHF FM service service, but with four times the peak frequency-deviation; they are intended for use in future work on the comparison of different modulation systems. A brief specification...
Topics: khz, receiver, mhz, tuner, amplifier, bbc, band, stereo, frequency, input, tuner unit, input...
R&D Report 1977-37 : Improvements to cheap loudspeakers H.D. Harwood, R. Matthews The sound quality of portable domestic audio equipment is limited mainly by the loudspeaker and cabinet. An investigation has been made to determine whether, at negligible extra cost, worthwhile improvements can be made. It is concluded that in some cases, small but worthwhile improvements are possible.
Topics: unit, loudspeaker, type, elliptical, khz, sound, bare, cone, treated, damping, circular unit, cheap...
R&D Report 1978-01 : A method for measuring echoes in the multipath propagation of v.h.f. signals. W.J. Christmas This report describes a method of measuring the amplitudes and delays of the echoes encountered in the multipath propagation of radio waves. The method uses a test signal transmitted on a spare line of a 405-line television signal (CCIR Standard A) and is therefore intended in the first place for use at VHF. The method could easily be extended to UHF.
Topics: signal, sequence, fourier, frequency, echo, test, transform, echoes, sampled, sampling, multipath...
R&D Report 1985-12 : DBS pay television: picture signal scrambling. M.J. Knee Picture signal scrambling methods suitable for a DBS MAC pay television channel are described. They use a technique known as 'rotation scrambling', which is shown to meet the likely requirements for picture quality, security against piracy, scrambling effectiveness and cost. The methods have been tested using experimental equipment and the results have led to an agreement within the EBU to incorporate them into...
Topics: scrambling, rotation, signal, scrambled, cut, dbs, picture, mac, descrambling, descrambled, signal...
R&D Report 1988-02 : The assessment of the colorimetric properties of light sources for use in television scene lighting. E.W. Taylor An account is given of the Television Consistency Index method of assessing the colorimetric properties of light sources for use in television scene lighting. Theoretical limits have been determined within which this Index may be used as a general description of lamp performance, bearing in mind the inevitable differences in spectral analysis characteristics...
Topics: consistency, colour, lamp, test, camera, reference, values, television, analysis, spectral,...
R&D Report 1995-08 : Low-delay predictive audio coding for the HIVITS HDTV codec A.K. McParland, N.H.C. Gilchrist This Report describes the work on predictive audio coding carried out by the BBC as part of the RACE âHIVITSâ project. The purpose of the work was to develop and demonstrate a low bit-rate audio codec with low delay for use with a digital HDTV (high definition television) signal coded by the HIVITS HDTV codec and capable of conveying at least 5 channels of audio within the...
Topics: audio, coding, predictors, hdtv, prediction, predictive, hivits, codec, coder, error, dsp dsp,...
R&D Report 1955-06 : The service area of the temporary television transmitter at Redmoss, Aberdeen. L.F. Tagholm, G.I. Ross, R.S.A. Sandell This report shows that the temporary transmitter at Radmoss, near Aberdeen, provides the city of Aberdeen with a reasonable television service using an effective radiated power of 3 watts. It is shown that the service will, in general, be similar to that expected from the final transmitter at Meldrum.
Topics: transmitter, aberdeen, temporary, redmoss, strength, vision, field, watts, field strength,...
R&D Report 1960-23 : Analogue computer for aerial radiation patterns H. Page, G.J. Phillips, J.A.S. Fox An analogue computer has been constructed to calculate the horizontal radiation patterns of aerial arrays comprising a number of radiating elements mounted on a central support mast. The radiation pattern of a single element must be known, and from this the pattern for a number of identical elements round the mast may be calculated. The currents in the elements may have any desired...
Topics: radiation, uniselector, circuit, wiper, elements, pattern, output, contacts, stepping, wipers,...
R&D Report 1961-19 : Visit to Germany covering transmitting installations and the 1961 Berlin Radio Show. G.J. Phillips, D.E. Todd A four-day visit to Germany was undertaken to see transmitting installations in North Germany and Berlin, and to visit the two-yearly German Radio Show, held this year in Berlin. In Hamburg we also had discussions at the Institut fur Rundfunktechnik (I.R.T.). Special attention was paid to work in Germany connected with u.h.f. television transmissions, primarily...
Topics: transmitter, transmitters, band, mast, aerials, transmitting, aerial, television, siemens,...
R&D Report 1963-21 : Service area of the Manningtree television transmitter. J.A. Butt, J.C. Westhorp This report presents the results of a field strength survey of the television transmitters at Manningtree. The service provided is very severely restricted by the high level of interference caused by United Kingdom co-channel stations and the Belgian television station located at Liege. Nevertheless, the principal towns in the service area are provided with a good service for a high...
Topics: manningtree, transmitter, strength, field, receiving, liege, aerial, interference, field strength,...
R&D Report 1963-66 : New transmitting aerial for the Hastings television station. D.W. Osborne A brief summary of the installation.
Topics: aerial, hastings, etn, horizontal, channel, templet, transmitting, gain, feeders, consists,...
R&D Report 1969-10 : Expansion of functions in terms of Chebyshev polynomials J.W. Head If f(x) is continuous and of bounded variation in the range x is greater than or equal to -1 and less than or equal to +1, it can be expanded in terms of Chebyshev polynomials. The numerical procedure for such expansion is given in detail. The reverse process of evaluating an expression for which the 'Chebyshev coefficients' are known is also fully considered, for cases in which these coefficients can be...
Topics: chebyshev, coefficients, polynomials, differential, terms, series, linear, equation, expansion,...
R&D Report 1970-35 : Band II FM sound broadcasting: Field tests at radio Nottingham using mixed polarisation J.G. Spencer Field tests have been carried out in the Nottingham area to investigate the effects of a change from horizontal to either circular or slant polarisation for Band II FM sound transmissions. The results show that there is little to choose between these two types of mixed polarisation from the point of view of reception. A change to either would be equivalent to a reduction...
Topics: polarisation, aerial, measurements, transmission, aerials, mixed, circular, reception, field,...
R&D Report 1970-38 : Satellite broadcasting: Spectrum efficiency of television services in the 12 GHz band G.J. Phillips The report is confined to a study of the use of geostationary satellites transmitting in the 12 GHz band to provide multiple television broadcast services within a wide area. The theoretical possibilities are first examined with reference to an ideal lattice of just-overlapping circular service areas. By proper assignment of satellite positions in the equatorial orbit and...
Topics: satellite, aerial, protection, receiving, lattice, satellites, transmitting, channel, service...
R&D Report 1956-21 : A comparison of CW interference effects on colour and monochrome television transmissions. A.V Lord, G.F. Newell This respect describes measurements of the interference by an unmodulated carrier with both colour and monochrome transmissions. The British 405-line system was used for both colour and monochrome transmissions, the colour system being a modified N.T.S.C. type. The results show that colour transmissions are more susceptible than monochrome transmissions to...
Topics: monochrome, colour, receivers, protection, transmission, ratios, interference, receiver,...
R&D Report 1965-29 : Tropospheric propagation measurements over mixed land and sea paths at 560 Mc/s E. Sofaer, J.W. Stark Field strength measurements of a transmission at 560 Mc/s were carried out over mixed land and sea paths at distances ranging from 198 km to 356 km. The results show that the attenuation, relative to an all-sea path, introduced by sections of land at the end of the path increases with distances from the coast. A method of estimating the attenuation due to the presence...
Topics: site, field, distance, curve, curves, path, measurements, strength, land, tropospheric, site...
R&D Report 1965-08 : Specification of the impedance of transmitting aerials for monochrome and colour television signals D.J. Whythe Any departure of the impedance of a television transmitting aerial from the characteristic impedance of its feeder results in the transmission of delayed signals. This report specifies the maximum departures of impedance that are permissible without visible distortion for 405-line and 625-line monochrome and colour television signals. The specifications for...
Topics: delayed, signal, aerial, impedance, feeder, signals, reflexions, monochrome, transmitter,...
R&D Report 1967-05 : The determination of dipole reactance by radiation pattern integration P.C.J. Hill A new method for determining the input reactance of a cylindrical dipole is given based upon the principle of analytic continuation of Poynting integration into the part of the radiation pattern outside the normal, or 'visible' region. The theoretical basis for this extension, recently described by Rhodes for the case of planar aerials, is re-stated here and then applied to cylindrical...
Topics: dipole, cylindrical, equation, reactance, radiation, aperture, integration, pattern, power,...
R&D Report 1966-38 : A phase-corrected video "notch" filter R.E. Davies, G. Edmondson Video "notch" filters are used in television apparatus to suppress unwanted spectral components in the video-frequency band; an important application is the suppressions of signal components at the colour-subcarrier frequency in the luminance channel of colour television equipment. However, the presence of a notch filter results in "ringing" whenever transients are present and...
Topics: filter, notch, phase, circuit, frequencies, bandwidth, components, frequency, signal, delay,...
R&D Report 1967-24 : An investigation of the law of displacement and of width of a stereophonic image for male speech H.D. Harwood An account is given of the present position, both in theory and practice, regarding the relation between the displacement of a stereophonic image and the corresponding interchannel difference in level. The disagreement amongst published results is indicated. Experiments are described which show that for male speech this relation is largely independent of the...
Topics: image, width, position, stage, circuit, frequencies, frequency, interchannel, listening,...
R&D Report 1968-46 : Calculation of the field strength required for a television service, in the presence of co-channel interfering signals. Part 3: The computer program R.W. Lee Parts 1 and 2, which have been issued separately, give the theory underlying the calculation processes which have been actually used in the BBC Research Department. Part 3 describes the original computer program used for carrying them out.
Topics: transmitter, field, terrain, location, test, interfering, calculation, strength, path, calculate,...
R&D Report 1971-32 : A feasability study of an adaptive system for UHF television D.E. Susans, J.G. Spencer This report describes the results of an investigation into the feasibility of producing an adaptive receiving system for UHF television suitable for rebroadcast links in situations where, with standard techniques, there would be unacceptable interference. The system is designed to adjust continuously the directivity pattern of a receiving aerial array so as to steer minima onto the...
Topics: interference, signal, adaptive, system, test, synchronising, waveform, aerial, pulse, aerials,...
R&D Report 1975-09 : A traffic information service employing time division multiplex transmissions. R.S. Sandell, M.W. Harman The use of broadcasting to provide traffic and road information to motorists continues to be developed, but there remain several problems. It would seem that a real improvement could be realised if it were possible to provide the driver with a service dedicated to his needs, but which would not overwhelm him with irrelevant data. The shortage of frequencies and other...
Topics: traffic, field, receiver, strength, frequency, stations, mute, announcements, tdm, bbc, local...
R&D Report 1977-04 : Two audio test-signal generators for assessing programme-related noise in digital compandors. W.I. Manson, D.F. Reid Certain forms of programme-quality impairment are, at present, best investigated subjectively. Natural sounds cannot be repeated precisely without using a recording process which may itself introduce some impairment, so their use as test signals for subjective investigations is somewhat limited. Synthetic signals, generated electronically, are attractive...
Topics: digital, signal, test, generators, noise, khz, envelope, output, quantum, shaper, department...
R&D Report 1977-07 : Satellite broadcasting: slant path attenuation through rain storms. J.L. Eaton A recently proposed statistical precipitation rate profile for isolated rain storms in the UK is employed to obtain the effective attenuation path length or 'effective distance' for storms lying directly in the transmission path from a broadcasting satellite operating in the 12 GHz band. This effective slant-path distance is a function of the elevation angle and distance from the storm...
Topics: attenuation, path, distance, storm, effective, intensity, rainfall, slant, storms, satellite, path...
R&D Report 1977-10 : UHF scatter propagation across the English Channel. G.H. Millard The incidence of scatter propagation in a trans-horizon path across the English Channel has been studied in order to assess the effect it has on the performance of a uhf television re-broadcast link to the Channel Islands. For small angles of scatter the degree of scattering observed was consistent with simple theory. The effect will result in a relatively minor degradation of link performance.
Topics: aerial, signal, scattering, interference, surface, kippure, aerials, directivity, scattered,...
R&D Report 1978-10 : Digital aperture correction. M. Weston An experimental digital aperture corrector has been constructed which provides vertical correction together with 'in-band' horizontal and 'out of band' horizontal aperture correction of the luminance component of 8-bit PCM Red, Green and Blue signals from an experimental digital signal processing channel. The vertical and horizontal aperture correctors operate in parallel on a 'luminance' signal matrixed from R, G, B inputs to...
Topics: correction, aperture, corrector, signal, horizontal, corrected, vertical, digital, frequency,...
R&D Report 1977-41 : A digital split-band compandor for 64 kbit/s coding of speech with s 7kHz bandwidth. W.I. Manson, D.W. Stebbings This Report describes a three-channel split-band digital compandor arrangement for coding a 7 kHz speech signal for transmission at 64 kbit/s. It was not practicable at the time to construct equipment for real-time evaluation, but the performance of a simulation has been assessed. The results obtained are regarded as promising, but the performance was...
Topics: khz, digital, companding, coding, system, compandor, sampling, speech, bandwidth, technique,...
R&D Report 1982-23 : The design of microcomputer-controlled equipment for the measurement of reverberation time. R. Walker, M.M. Leather The practical methods of measuring reverberation time are discussed briefly. The design of a microprocessor controlled system for measuring reverberation time in a wide range of different types of rooms is described. The system employs analogue signal processing to provide the loudspeaker excitation signal and to receive and process the microphone output...
Topics: reverberation, frequency, amplifier, display, signal, filter, data, microphone, measurement, range,...
R&D Report 1980-06 : A study of peak multiplexed signal level in the context of 2 1/2- or 3-channel surround-sound transmissions. E.W. Taylor The effect on peak multiplexed signal level of quadrature modulating the 38kHz subcarrier of a pilot-tone stereophonic system with the third of 'T' signal of a 2.5 or 3-channel System UHJ surround-sound transmission is discussed. Theoretically-derived values are compared with measurements made using test material received during Independent Local...
Topics: signal, peak, multiplexed, level, equation, phase, signals, subcarrier, sin, pilot, phase shift,...
R&D Report 1982-21 : Broadcast telephone speech: use of speech synthesis to extend the audio bandwidth. P.S. Gaskell, W.I. Manson, T.A. Moore Speech signals received over the public telephone network are increasingly being used in broadcasting, particularly for contributions from correspondents and commentators and in the "phone-in" type of programme. Though telephone - speech quality is normally adequate for communicating information it can compare very unfavourably with studio...
Topics: speech, synthesis, telephone, prediction, pulses, signal, components, pitch, synthesised,...
R&D Report 1954-13 : The Klein-Plessey Ionophone loudspeaker. J.R. Chew A novel type of loudspeaker, known as an "Ionophone", has been tested. In this loudspeaker the conventional vibrating diaphragm is dispensed with and the sound is produced by a modulated r.f. corona discharge. The device is used in conjunction with a horn radiator and its main field of application is therefore in the high-frequency range; smooth response can be obtained up to at least 20 kc/s. In its present...
Topics: frequency, ionophone, horn, distortion, output, tuning, loudspeaker, axial, corona, overload,...
R&D Report 1955-19 : The application of correlation methods and phase-coherent detection to room acoustics. M.W. Greenway, C.L.S. Gilford. In an attempt to produce an improved method of displaying the acoustic behaviour of a room, an investigation has been made into some phase-sensitive and correlation methods. In particular, a phase-coherent modification of the pulsed glide type of display has been developed, in which the microphone output is modulated by the original frequency of...
Topics: coherent, glide, pulsed, display, logarithmic, output, correlation, frequency, studio, tone,...
R&D Report 1962-27 : The variation in the visibility of interference over the grey scale of a television picture. W.K.E. Geddes Subjective measurements have been made in order to establish the relative visibility, at different points on the grey scale, of interference superimposed on a television picture. Results are compared and contrasted for a number of distinct types of interfering signal.
Topics: visibility, noise, signal, test, level, grey, values, brightness, coherent, curves, television...