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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 1966-18 : K-rating of lenses. A.H. Jones The subjective quality of lenses and the performance of television apparatus may be described by means of Figures of Merit and K-ratings respectively; in this report factors influencing these quantities are examined. The K-ratings of a number of lenses are worked out and it is found that a relationship exists between the K-rating and one of the two quantities determining Figure of Merit; a formula expressing this relationship is derived....
Topics: lens, lenses, waveform, merit, relationship, sharpness, spectrum, optical, fie, apparatus,...
R&D Report 1963-54 : Service area of the Morecambe Bay television transmitter. H.T. Madoc-Jones, J.A. Carter The results of a field strength survey of the Morecambe Bay television transmitter are given in this report.
Topics: morecambe, bay, transmitter, field, television, bowness, holme, strength, aerial, windermere,...
R&D Report 1983-16 : A range of combined error correction and recording channel code schemes M.A. Parker This report describes an error corrections scheme which uses the inherent error detection capability of a channel code as one dimension of the correction process. This reduces the total overheads in terms of hardware and data rate required for correction, allowing the advantages of a channel code whilst minimising the overheads.
Topics: error, errors, burst, correction, code, coding, parity, channel, word, data, correction scheme,...
R&D Report 1955-14 : The measurement of the flow-resistance of acoustic materials. C.L.S. Gilford This report describes methods developed for the measurement of the flow resistance of acoustic materials under direct and alternating flow conditions.
Topics: resistance, flow, resonator, pressure, method, measurements, measurement, sample, acoustic,...
R&D Report 1966-17 : Transmitting aerial for the Brecon VHF sound station. D.W. Osborne The Brecon v..h.f sound relay station came into operation on 20th December 1965. It provides a service to Brecon and its immediate environs and also to the village of Llanspyddid.
Topics: aerial, transmitting, pole, receiving, wooden, templet, horizontal, brecon, udc, etn, transmitting...
R&D Report 1975-29 : A reflection modulator for adding data to a composite television signal at UHF. P. Shelswell A basic reflection modulator cannot be used to add data to a composite television signal at UHF. This report describes the modifications which must be made to a reflection modulator so that it can be used for this purpose. Particular attention is given to the addition of narrowband data to lines in the field-blanking interval. There is a discussion of electronically-variable...
Topics: modulation, diode, frequency, reflection, signal, filter, pin, modulator, modulate, carrier,...
R&D Report 1974-10 : CEEFAX: Interference with television from data signals transmitted in the field-blanking period G.M. Le Couteur This Report presents the results of engineering broadcast tests which were carried out during the early part of 1973 to examine the suitability of certain lines in the television field-blanking interval for the transmission of CEEFAX digital data signals. It was concluded that lines 17 and 18 were preferred for this purpose.
Topics: data, lines, tests, sawtooth, impairment, flyback, observers, test, picture, interference, vertical...
R&D Report 1985-05 : The improved display of 625-line television pictures: adaptive interpolation. A. Roberts Some of the defects of a conventional 625-line television scanning system can be reduced or even eliminated by signal processing in the receiver. The processing need not be very complicated and most scanning system defects can be treated merely by raising the display scanning rate by standards conversion, for example to a sequential structure of 625-lines at 100 pictures a second or...
Topics: motion, algorithm, detector, interpolation, detail, output, vertical, interpolator, algorithms,...
R&D Report 1990-07 : Satellite broadcasting: a common-frequency approach to wideband HDTV with a hand-made example 'plan' J.H. Stott The generation and analysis of a "hand-made" plan for satellite broadcasting are described. The plan is intended as an example of what could be achieved within any band which may be allocated for wide-band HDTV at a forthcoming World Administrative Radio Conference. It is shown that the whole of such a band could be used by every country...
Topics: ghz, orbit, hdtv, countries, frequency, interference, band, antenna, satellite, modulation,...
R&D Report 1966-11 : Acoustic tests in Dubbing Suite 1, East Block, Television Centre. D.K. Jones The installation of a new Dubbing Theatre and its associated Mixer and Recording Rooms has recently been completed in the East Block at Television Centre. Reverberation times and noise levels were measured in the three rooms and the sound insulation between the rooms taken in pairs was obtained. The results are given in Section 2, and their implications are discussed in Section 3.
Topics: reverberation, mixer, insulation, recording, noise, rooms, theatre, dubbing, sound, room,...
R&D Report 1968-22 : Salisbury UHF relay station: Summary of installation G.H. Millard Brief data sheet detailing equipment used, frequencies, radiation characteristics etc, together with graphs of horizontal and vertical radiation patterns.
Topics: salisbury, vertical, radiation, relay, broadcasting, technological, horizontal, transmitter,...
R&D Report 1969-43 : A camera tube lag meter M.J. Mortimore, I.D. Chisholm The exposure of a camera tube to a brief flash of light and the measurement of the magnitude of the signal current after a known number of television fields can provide an indication of the speed of response of the tube to changing light levels. A meter which permits accurate measurements, in the presence of noise, to within an accuracy of plus or minus 0.1% of white level is described and its performance is...
Topics: tube, lag, illumination, output, source, samples, light, sampling, magnitude, camera, sampling...
R&D Report 1964-43 : Service areas of the Wenvoe television (Band I) and VHF sound transmitters R.C. Vercoe, H.T. Madoc-Jones, J.H. Causebrook, J.A. Carter This report gives the results of a re-survey of the television (Band I) transmission and a survey of the v.h.f. sound transmission. The re-survey of the television transmission is more detailed than the original survey carried out in 1952.
Topics: television, strength, median, transmitters, field, aerial, wenvoe, sound, field strength, exceeded,...
R&D Report 1957-05 : Colour television: The adaptation of the NTSC system to UK standards Part 3: A triple video channel for use with a colour slide or film scanner. A.V. Lord, S.J. Lent A triple video channel has been developed for use with colour slide or film scanning apparatus. This channel includes al the signal correction and modifications necessary to provide standard colour separation signals suitable for coding. An outline is given of the considerations influencing the design; the...
Topics: corrector, signal, afterglow, gamma, output, aperture, correction, characteristic, pulses, pulse,...
R&D Report 1970-09 : UHF television: the interference caused by a receiver operating on channel n to an adjacent receiver tuned to n+4 J.G. Spencer The interference that a television receiver tuned to a UHF channel n can cause to a neighbouring receiver tuned to channel n + 4 was considered in the early stages of development of the UHF plan. It then appeared that this type of interference could constitute a serious impairment of the quality of a colour television service at UHF. Since that...
Topics: receiver, interference, aerial, mhz, receivers, channel, coupling, frequency, strength, tuned,...
R&D Report 1990-06 : NICAM 728 -- digital two-channel sound for terrestrial television A.J. Bower This report describes the development and technical specification of the NICAM 728 system for broadcasting digital two-channel sound with terrestrial television transmissions. NICAM 728 conveys two high-quality digitally-coded sound signals along with the picture and monophonic FM sound signals of the existing system I and systems B, G and H terrestrial television transmission standards. The...
Topics: nicam, sound, digital, system, data, television, carrier, signal, parity, signals, digital stereo,...
R&D Report 1976-06 : Diversity reception at high-frequencies using the single-sideband mode. D.E. Susans When using long-distance HF and SSB re-broadcast links it is customary to use dual-diversity reception. This method of reception has considerable advantages over a single-channel under conditions of 'flat' fading but it has been reported that any improvement is only marginal when the fading is predominantly frequency-selective. The reasons for this are discussed and a new correlation...
Topics: fading, audio, combiner, signals, phase, output, signal, diversity, receiver, correlation, fading...
R&D Report 1965-45 : UHF transmitting aerial for the Winter Hill television station G.H. Millard A summary of the installation of the UHF Transmitting Aerial for the Winter Hill Television Station.
Topics: aerial, channel, radiation, mast, horizontal, vision, triangular, feeder, bbc, transmitter,...
R&D Report 1975-14 : Specification of the timing stabilities of broadcast monochrome and PAL colour television signals. J.R. Chew, D.W. Stebbings The subjective effects of timing instabilities in television signals have been studied. In Part 1 of the Report, movements of the monochrome picture due to fairly large timing errors are considered, and the effects of the performance of the receiver horizontal-synchronising circuits are explored. For the simple case in which the timing error is a...
Topics: timing, perturbations, frequency, signal, impairment, phase, subcarrier, flywheel, synchronising,...
R&D Report 1954-25 : Visibility of random noise in a television picture M. Gilbert This report describes an investigation into the relative visibility of narrow bands of noise within a 3 Mc/s video bandwidth. This is an essential preliminary to the assessment of the relative annoyance of different types of noise spectra on the television picture. A set of curves has been deduced and a suitable network has been proposed.
Topics: noise, visibility, attenuation, annoyance, band, frequency, random, threshold, score, bands,...
R&D Report 1960-28 : A comparision of the aerials used during the U.H.F. television survey of 1957/8 E.W. Taylor The three Band V aerials used during the Band I/Band V comparison tests are described and their performances are compared, comparisons with a dipole are also included. The relative effect of small changes in aerial position, and the factors governing the choice of aerial at any given site, are discussed.
Topics: aerials, aerial, dipole, comparison, subjective, received, array, tests, transformer, ratio,...
R&D Report 1963-36 : Varotal V. A 10 to 1 zoom lens for the image orthicon format (No 617566) W.N. Sproson Measurements are reported on the zoom lens Varotal V. These include modulation transfer factor, vignetting, transmission and veiling glare and geometrical distortion. An overall assessment based on sharpness and vignetting is given and comparisons are made with other lenses, both of fixed focal-length and of varifocal length.
Topics: focal, aperture, lens, modulation, lenses, length, zoom, varotal, curves, transfer, geometrical...
R&D Report 1978-06 : Automatic colour control using a microprocessor. R.P. Marsden This Report describes the principles of operation and methods of programming a microprocessor used to control a video colour corrector. The equipment was designed as part of a study of the application of microprocessors in television. The range of application and the problems of testing microprocessor systems are also discussed. It is concluded that a well designed system can eliminate most of the low and...
Topics: microprocessor, colour, corrector, automatic, pulses, control, circuits, program, signals, manual,...
R&D Report 1974-32 : UHF amplifiers: improvement of linearity by pre-correction A.G. Lyner, P. Shelswell The basic principle of pre-correction for improving amplifier linearity is discussed with some theory and the idea of pre-correction using an error signal injection system is introduced. A description is given of a practical form of pre-corrector which was used successfully to double the output power of a transistor amplifier for a UHF television combined sound and vision signal.
Topics: signal, amplifier, output, attenuator, power, amplitude, input, error, coupler, couplers, main...
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 1956-26 : The service area of the Meldrum television transmitter. R.S. Sandell The service area of the Meldrum television transmitter conforms with that predicted from the site tests. Most of north-east Scotland, east of a line from Burghead to Montrose, is within the nominal (100 UV/m) service area. The east coast of Sutherland and part of Caithness receive a fringe service.
Topics: meldrum, transmitter, strength, interference, contour, horizontal, aberdeen, field, field strength,...
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 1968-15 : Kingussie VHF relay station: Summary of installation R.D.C. Thoday, J.P. Crean Brief data sheet detailing equipment used, frequencies, radiation characteristics etc, together with graphs of horizontal and vertical radiation patterns.
Topics: aerial, band, transmitting, aerials, pole, horizontal, receiving, etn, tier, installation,...
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 1978-22 : Narrow-band FM system for television links: tests of performance under conditions of multipath propagation. N.H.C. Gilchrist Mobile transmitters have a number of uses in television outside broadcasts; examples are found in the coverage of horse-racing, where a television camera mounted on a moving road vehicle provides close-up pictures of competitors, and also at golf tournaments and boat-races, where helicopters have been used to carry cameras. Multi-path propagation...
Topics: receiver, multipath, threshold, roving, signal, balloons, system, synchronism, limiter, videotape,...
R&D Report 1993-12 : Predicted coverage of a COFDM Single Frequency Network for UHF digital terrestrial TV broadcasting M.B.R. Lee The Coded Orthogonal Frequency Division Multiplex (COFDM) transmission system provides a very high degree of tolerance towards multipath interference. Three factors contribute towards this tolerance; the inclusion of a guard interval, coding to provide error correction and the division of the digital data amongst a very large number of low bit rate carriers. It...
Topics: coverage, antenna, guard, digital, field, directional, interval, transmitters, bbc,...
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 1972-37 : The contrast handling requirements of a colour television display R.N. Robinson A survey of domestic television viewing conditions is described. These conditions were reproduced in a laboratory in order to determine the contrast range of the eye. The dependence of the contrast range visible to the eye upon ambient illumination and upon the form and brightness of the displayed picture have been investigated; these results are then interpreted in terms of the contrast...
Topics: luminance, tube, ambient, display, subjective, reflectance, flare, viewing, contrast, light,...
R&D Report 1972-12 : Variation of low-frequency sky-wave field strength with solar activity in Europe. P. Knight, J.P. Crean Low-frequency sky-wave field strengths measured late at night during the solar cycle have been analysed, but no clear dependence on solar activity has been found. It is therefore recommended that the influence of solar activity on low-frequency sky-wave field strength should be disregarded for the time being.
Topics: regression, solar, measurements, strength, activity, variation, allouis, field, coefficients,...
R&D Report 1962-14 : Co-channel interference between television signals of the same or different standards. G.F. Newell, E.W. Taylor This report describes measurements of the ratios of the amplitudes of wanted and interfering signals which produce a particular subjective grade of interference. The measurements were made in order to ascertain the required protection ratios for mutual interference between two stations each operating on any of the three television standards at present in use...
Topics: interference, offset, signal, protection, frequency, ratios, offsets, interfering, required,...
R&D Report 1961-02 : Reflectometer equipment for use at high-frequency transmitting stations A. Brown, G.H. Millard Equipment has been developed for measuring the output power of the transmitters, and the reflection coefficient of the associated balanced transmission lines, at B.B.C. high-frequency (h.f.) transmitting stations. It consists of two directional couplers, one sampling the forward wave, (and thus measuring the transmitter power if the reflection coefficient is small), and the...
Topics: reflection, directional, coefficient, power, transmitter, equipment, coupler, transmission,...
R&D Report 1961-12 : AKG electrostatic microphones Types C26 and C28. H.D. Harwood, J.R. Chew, R.L. Deane, R.J. Packer This report describes tests on two electrostatic microphones manufactured by the Akustische und Kino-Gerate Gesellschaft (A.K.G.). The first, type C26, has omnidirectional and the second, type C28, cardioid characteristics. The microphones are of small dimensions and provision is made in each case for introducing an extension piece between the capsule and the head...
Topics: type, microphone, capsule, extension, interference, impedance, characteristics, frequency, noise,...
R&D Report 1954-33 : The service area of the temporary television transmitter at Douglas, Isle of Man. R.A. Rowden, S.J. Ashdown This report gives the results of a survey of the service area of the temporary television transmitter at Douglas, Isle of Man.
Topics: transmitter, strength, field, isle, transmitters, average, power, temporary, field strength,...
R&D Report 1954-11 : The specification of the reflection coefficient of a F.M. aerial. G.D. Monteath If an aerial radiating f.m. transmissions is not matched to its feeder, amplitude modulation is introduced and the a.f. signal suffers non-linear distortion. The distortion is most marked if the receiver lacks a limiter. These effects are examined in this report and a limit for the reflection coefficient at the aerials is proposed. This constitutes a considerable relaxation of the...
Topics: amplitude, distortion, feeder, reflection, receiver, instantaneous, harmonic, frequency, maximum,...
R&D Report 1963-48 : Normende 'Transita' transistor AM/FM portable receiver. P.J.E. Harvey This report gives the results of tests on the Nordmende 'Transita' Transistor portable receiver on the v.h.f. range. The performance of the receiver is impaired by distortion in the audio output stage.
Topics: receiver, output, distortion, ratio, frequency, input, deviation, signal, measured, sensitivity,...
R&D Report 1962-44 : Fluctuation noise in two forms of the NTSC colour television system. A.V. Lord A recently proposed modifications to the coding of NTSC-type colour television claims to offer some improvements in the picture displayed by both colour and black-and-white receivers. The effects of fluctuation noise in colour receivers are investigated for both the modified system and the normal form of NTSC system. The analysis assumes that "flat-spectrum" noise is added to the...
Topics: noise, luminance, ntsc, decoder, fluctuation, colour, decoding, signal, synchronous, chrominance,...
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 1963-18 : Visibility of small luminance perturbations in television displays. G.F. Newell, W.K.E. Geddes Measurements of the visibility of small-magnitude luminance perturbations at various parts of the grey scale have been carried out using television displays. (This report includes, in a revised and condensed form, material already published in Research Department Reports T-083 and T-092, as well as the results of further work carried out since these reports were written). The...
Topics: luminance, visibility, noise, random, displayed, pattern, test, signal, experiments, perturbing,...
R&D Report 1964-53 : Comparisons between three colour television cameras C.B.B. Wood Tests have been carried out to compare the performance of an experimental four-tube colour camera developed by E.M.I. Ltd, a three-tube plumbicon colour camera manufactured by Phillips and a three-tube image orthicon colour camera manufactured by Marconi, the output of each camera being, in each case, an NTSC coded signal. Subjective comparisons are described and discussed of the pictures obtained when...
Topics: camera, orthicon, plumbicon, tube, subjective, cameras, image, colour, luminance, lipstick, fine...
R&D Report 1964-66 : Visit to School of Radiometeorology, .Lagonissi, Greece, September 1964 P. Knight A report on a visit to the School of Radiometerology in Lagonissi in Greece by the author in September 1964.
Topics: refractive, propagation, measurements, atmosphere, frequencies, meteorological, waves, aerial,...
R&D Report 1968-06 : Experimental equipment for converting television signals into digital signals and vice versa V.G. Devereux, M.T.A. Salter The report describes equipment which has been constructed for converting a television signal into digital form and reconverting to conventional form. The television signal is sampled at a rate of 13 million samples/sec and a 6-bit digital signal is derived which indicates the magnitude of each sample as one of 64 binary numbers. It was found that...
Topics: signal, digital, pulses, video, sample, unit, quantized, signals, output, converter, weighting...
R&D Report 1965-53 : Band III transmitting aerial for the Sandale television station D.W. Osborne A summary of the Band III transmitting aerial for the Sandale Television Station.
Topics: aerial, transmitting, sandale, horizontal, tier, transmitter, height, band, templet, mast,...
R&D Report 1966-58 : Television sound transmission by modulated pulses in the line-blanking intervals A.V. Lord This report reviews the properties of modulated pulses with particular reference to their application to television sound transmission. It is shown that combinations of modulated pulses and video signals could prove practicable for both broadcasting and link purposes.
Topics: pulse, pulses, modulation, sound, sampling, amplitude, signal, frequency, ratio, modulated, uniform...
R&D Report 1965-48 : Compatible single-sideband modulation: Comparisons with double-sideband modulation over high-frequency circuits. D.J. Whythe Field tests are described which investigate the transmission of compatible-single-sideband signals from a typical high-power transmitter for high-frequency broadcasting and which compare reception of double-sideband and compatible single-sideband signals over circuits of some 3,000 and 7,000 miles (5,000 and 11,000 km). The tests show that, given...
Topics: modulation, modulator, sideband, transmitter, hrs, signal, frequency, transmissions, tests,...
R&D Report 1968-09 : U.H.F. Transmitting Aerial for the Sudbury Television Station G.H. Millard A u.h.f. transmitting aerial for the Suffolk area has been built as a top-mast on the new BBC mast at Sudbury. The station started trade tests on 27th January 1968 and full service on 10th February 1968.
Topics: aerial, bbc, channel, mast, transmitter, transmitters, feeder, radiation, transmitting, etn,...
R&D Report 1968-11 : The impairment caused by phase-perturbation of the colour sub-carrier in a colour television system of the NTSC type D.W. Osborne This report describes subjective tests which were made to determine the picture impairment introduced when the quadrature-modulated chrominance sub-carrier in a colour television system of the NTSC type is subjected to a systematic switched phase-perturbation. The tests showed that the system is particularly susceptible to disturbances of...
Topics: impairment, colour, ntsc, perturbation, tests, waveforms, phase, waveform, picture, subjective,...
R&D Report 1968-53 : Bedford VHF relay station: Summary of installation R.D.C. Thoday, J.P. Crean Brief data sheet detailing equipment used, frequencies, radiation characteristics etc, together with a graph of horizontal radiation.
Topics: transmitting, aerial, band, bedford, transmitter, bbc, installation, horizontal, receiving, tower,...
R&D Report 1968-40 : A set of phosphors for use in a colour telerecording display E.W. Taylor, G.D. Judd The spectral and actinic characteristics of three phosphors (red, green and blue) for use in a colour-telerecording display are described. Absorption-type filters are specified for shaping their emission spectra.
Topics: phosphors, phosphor, spectral, actinic, exposure, display, telerecording, cathode, filters,...
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 1970-01 : Detemination of the current distribution for aerial arrays of collinear elements with any number of sidelobes having equal maxima J.W. Head A 'normalized radiation pattern' is derived initially for a system having only four equally spaced elements. The general nature of a 'normalized radiation pattern' with good sidelobe suppression ratio is then discussed, and the relevance of Chebyshev polynomials is considered. A general formula for the feed currents in each aerial...
Topics: sidelobe, suppression, radiation, chebyshev, ratio, beamwidth, equation, normalized, elements,...
R&D Report 1976-01 : Digital video recording: some experiments in error protection C.D. Mathers This report describes two error-protection systems which were designed for use with the experimental digital television recorder. These systems were developed as part of a more general investigation into error protection for digital television recording. In the first, concealment of error bursts is controlled by a detection system based on parity bits which constitute 4.8% of the total data rate....
Topics: parity, error, concealment, data, digital, correction, bits, errors, bursts, word, parity bit,...
R&D Report 1977-38 : Experimental 704 kbit/s multiplex equipment for two 15 kHz sound channels. D.F. Reid, N.H.C. Gilchrist An outline description is given of equipment which converts two high-quality audio signals into digital form, and digitally compands and codes them into a single time-division multiplex signal with a bit rate of 704 kbit/s. The equipment is primarily intended to operate with a four-phase differential phase-shift keying modem and it incorporates special measures in the...
Topics: parity, framing, frame, khz, equipment, error, signal, digital, bbc, bits, sound channels, sending...
R&D Report 1976-09 : Ceefax: initial field trial at UHF of unified standard M.G. Croll A short series of field trials was conducted in late 1974 to assess the effects of some changes in the specification of the transmitted CEEFAX data waveform brought about by adopting the unified standard parameters. The results of 24 site tests indicate that these changes reduced the minimum field strength required for a marginal CEEFAX service by about 3.5 dB. The field strength for half the characters...
Topics: ceefax, field, unified, data, sites, trials, interference, uhf, signal, bbc, ceefax service, bit...
R&D Report 1973-38 : Holography: A general survey E.W. Taylor The history of the development of holography is surveyed and an introduction to the general theory is given. Techniques for the preparation of holograms are described, and materials for use as holographic recording media are discussed. An extensive list of references is included.
Topics: holographic, hologram, beam, interference, image, photographic, radiation, object, light,...
R&D Report 1973-32 : Solid state sensors: The use of a single dimension 512 element array for film scanning D.T. Wright Following some early experiments with a 72 element self-scanned linear array of photo-diodes, a 512 element array was obtained. This has been used to scan continuously moving film since this provides a convenient means of assessing the potential of single dimension solid state image pick up devices. The method of application and the resulting performance are discussed.
Topics: array, output, film, signal, mhz, scanning, scanned, clock, lens, saturation, stored correction,...
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 1973-08 : Computer program: MF sky-wave interference J.L. Eaton, A.M. Bunting A short self-contained computer program for calculating sky-wave interference at MF has been written. The program employs a simple empirical law for calculating field-strength and makes a correction for the transmitting aerial vertical radiation pattern, the take-off angle being derived from the great circle distance and the number of 'hops'. Protected field-strengths are calculated for each wanted...
Topics: transmitter, frequency, transmitters, interference, bbc, weighting, program, interfering, ccir,...
R&D Report 1993-02 : Digital sound: subjective tests on commentary-quality codecs N.H.C. Gilchrist, A.J. Oxenham Subjective tests have been carried out on five commentary-quality audio codecs on behalf of CCIR Task Group 10/2. All codecs operated at a bit rate of 60 kbit/s per mono signal, and were tested in both mono and stereo configurations. Significant differences in performance were found. All codecs introduced some impairment on the most critical programme items.
Topics: mono, codecs, stereo, grades, audio, tests, bbc, codec, material, digital, khz sampling, department...
R&D Report 1996-09 : A comparison of motion-compensated interlace-to-progressive conversion methods G.A.Thomas The conversion of interlaced video to progressive format may be carried out in a number of ways, including simple vertical interpolation, fixed or motion-compensated vertical-temporal interpolation, and approaches based on motion compensation using non-uniform sampling theory. Motion-compensated methods are the only ones which offer the possibility of maintaining high vertical...
Topics: vertical, filter, field, vectors, vector, filters, motion, temporal, errors, picture, motion...
R&D Report 1966-43 : Simple application to broadcasting of the results of subjective tests. R.D.A. Maurice The report discusses some different scales of criteria suitable for subjective tests for broadcasting applications and mentions a method of using the statistical results of subjective tests that may make maximum use of them aid management decision making.
Topics: subjective, impairment, grade, assessments, gaussian, statistical, tests, broadcasting, percentage,...
R&D Report 1974-03 : LF and MF propagation: Sky-wave field-strength prediction P. Knight During the night, medium-frequency sky-waves propagate to great distances via the ionosphere. The report describes the various factors which affect the waves as they travel from transmitter to receiver. Several methods which can be used for estimating the strength of sky-wave signals are compared.
Topics: curves, propagation, loss, ionospheric, wave, magnetic, coupling, polarisation, ccir, variation,...
R&D Report 1979-17 : Digital sound: sampling-rate synchronisation by variable delay. N.H.C. Gilchrist In a situation where a number of digital sound signals, all from sources operating at nominally the same sampling frequency, need to be processed, a variable delay technique may be used to synchronise the signals at the input to the processor. This Report describes experimental equipment which changes the sampling rate of a digital sound signal by using a variable delay which is...
Topics: synchroniser, sampling, digital, signals, signal, reset, samples, store, input, delay, sample...
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 1977-28 : Couteur The electronic concealment of blemishes on the output of solid state image sensors. G.M. Le Couteur This report discusses the nature and importance of blemishes which can occur on pictures produced by different types of solid state image sensor. The distraction and annoyance caused to the viewer by these blemishes can have a serious effect on the subjective quality of pictures, since in general blemishes are only tolerable at extremely low levels. The types of...
Topics: blemishes, clock, sensors, dark, output, signal, photodiode, concealment, blemish, variations,...
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 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 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 1987-04 : SPECOL: A colorimetric measurement system. A. Roberts This report describes a newly constructed colour measurement system comprising a light detector and a microcomputer. The light detector is a monochromator which can be tuned over the entire wavelength range of visible light so that spectral energy distributions of all types of light sources can be measured. The computer has direct control over the monochromator and can derive the chromaticity coordinates of the light...
Topics: colour, chromaticity, spectral, measurement, measurements, coordinates, cie, tristimulus,...
R&D Report 1989-13 : A digital HDTV recorder using a cluster of four D1 DVTRs. P.R. Burfield This report outlines the design philosophy of a digital HDTV video recording system that has been constructed from four conventional D1 digital video component recorders. Technical specifications of the recorder are given with explanations of how the system can be used to edit source material into good quality programmes. At present, the HDTV recorder is housed in a mobile laboratory together with...
Topics: hdtv, digital, recorder, recorders, mhz, sync, replay, video, chrominance, audio, edit controller,...
R&D Report 1991-14 : HDTV sound: programme production developments D.J. Meares The success or otherwise of multichannel sound with HDTV will depend to great extent on the programme makers being able sensibly to exploit the sound system in order to enhance the listening/viewing experience. This report documents the BBC's programme experiments over a period of about two years and presents the conclusions of that work.
Topics: sound, surround, stereo, hdtv, multichannel, channels, compatibility, channel, microphones,...