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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 1956-35 : A survey of factors limiting the performance of magnetic recording systems. E.D. Daniel, P.E. Axon, W.T. Frost. Magnetic recording is now firmly established as a system of storing information, using the term in its broadcast sense, in the scientific, artistic and commercial fields. It is the purpose of the present article to examine such elements as heads, recording media and tape transport systems, which determine the frequency and other characteristics of the magnetic...
Topics: recording, tape, reproducing, magnetic, signal, core, head, frequency, wavelength, bias, short...
R&D Report 1962-41 : The Sennheiser Type MD 82 and Electrovoice Type 642 microphones. W.I. Manson The Sennheiser type MD 82 and Electrovoice type 642 are both directional microphones in which sound is received through openings along a narrow tube. Type MD 82, a number of which are in use in the Corporation, is no longer in regular production but is included in this report for comparison with the currently available type 642. Measured frequency characteristics and polar patterns are given.
Topics: type, microphone, frequency, microphones, directivity, electrovoice, impedance, bass, sennheiser,...
R&D Report 1973-22 : Directional coupler design. G.W. McNally The design and performance of directional couplers are investigated with examples of 0 dB, 6 dB and 15 dB couplers being detailed to illustrate the configurations and construction methods used.
Topics: coupler, bbc, coupling, impedances, characteristic, strips, stripline, impedance, coupled,...
R&D Report 1960-17 : Sound insulation and acoustics of the new studios in the Centre Block, Bush House. C.L.S. Gilford This report describes the design, with respect to acoustics and sound insulation, of the studios recently built in the Centre Block of Bush House. The principles of design are not new but in this application there was considerable compromise on grounds of cost and appearance. The first section, dealing with sound insulation, describes how the design was started from a new...
Topics: studios, studio, insulation, reverberation, absorption, transmission, cubicle, sound, cubicles,...
R&D Report 1985-03 : Further developments of CCD line-array telecine. I. Childs In recent years there have been several advances in technology relevant to the use of solid-state line-array sensors in telecine applications. This Report will examine the improvements in performance of recent generations of line-array sensors, together with the further benefits obtainable by using improved signal processing. The use of digital storage as a necessary part of a line-array telecine also opens up...
Topics: film, dirt, sensor, concealment, telecine, scan, output, signal, sensors, ccd, double sampling,...
R&D Report 1977-18 : CEEFAX: field trials at VHF using System B - Bavaria - April 1975. M.G. Croll, D.T. Wright Tests have been conducted to assess the suitability of the Teletext unified-standard parameters for use with the vhf System B television standard. This work was undertaken jointly by the BBC and the IBA with the co-operation of the IRT. Apparatus was also made available for the tests by members of BREMA and by a German manufacturer of professional equipment. Field tests were...
Topics: teletext, receiver, signal, data, domestic, sites, transmitter, tests, aerial, criterion, teletext...
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R&D Report 1959-23 : Long distance overland propagation measurements at 180.4 Mc/s. J.W. Stark, K.H. Green, S.J. Ashdown, J.M. Caine, I. Rhodes This report presents the results of field strength measurements of v.h.f. transmissions on 180.4 Mc/s overland paths at distances up to 294 miles (473 km). These measurements extended over a period of approximately 3 1/2 years and have been used in the preparation of field strength/distance curves for various percentages of the overall time. The...
Topics: site, field, strength, pontop, propagation, receiving, coldfield, mursley, trees, sutton, permanent...
R&D Report 1995-14 : Digital HDTV bit-rate reduction in the studio T. Vlachos, M.G. Croll Two novel source coding algorithms are presented which are suitable for the recording of digital High Definition Television signals. One of the bit-rate reduction schemes is based on the Wavelet Transform and the other on the Lapped Orthogonal Transform (LOT). According to the first scheme, a multi-layered, hierarchical description of the source signal is obtained by means of a quad-tree, half-band...
Topics: coding, wavelet, transform, quantiser, block, quantisation, digital, frequency, compression,...
R&D Report 1954-31 : The performance of some American convertors and tuning units for television reception in the U.H.F. band. R.V. Harvey, G.F. Newell The results of tests on some current American u.h.f. television converters and tuning units are described. The performance of the better types is extremely good; the noise factor is low, and the drift of the local oscillator frequency after switching on is not excessive in view of the current American practice of intercarrier reception of...
Topics: oscillator, frequency, tuner, converter, tuning, strips, mixer, circuit, triode, diode, germanium...
R&D Report 1967-57 : The design of studio monitoring loudspeakers Types LS5/5 and LS5/6 H.D. Harwood, S.A. Hughes Details are given of the various factors which have led to the design of two new monitoring loudspeakers suitable for use in studios and outside broadcasts. The loudspeakers are much smaller than those of the present type; a floor standing model is designated type LS5/5, and one intended for hanging is called type LS5/6. In the course of the design, the questions of bass...
Topics: frequency, unit, loudspeaker, slit, axial, type, bass, khz, loudspeakers, characteristics, axial...
R&D Report 1968-48 : The performance of an 18:1 zoom lens for the Plumbicon format: The P. Angenieux 18x27.5 E31 No 1213679 K.J. Wright This report details the measured optical performance of the P. Angenieux 18x27.5 E31 lens, an 18:1 zoom lens specifically designed for use with the EMI type 2001 four-plumbicon colour camera. The measurements reported upon are for the transmission, veiling glare index, vignetting and modulation transfer function at full and reduced apertures. The measured...
Topics: focal, lens, zoom, length, vignetting, image, spatial, aperture, angenieux, modulation, full...
R&D Report 1993-09 : The HDTV digital audio matrix A.J. Mason Multichannel sound systems are being studied as part of the Eureka 95 and Radio-communication Bureau TG10-1 investigations into High Definition Television. One emerging sound system has five channels; three at the front and two at the back. This raises some compatibility issues. The listener might have only, say, two loudspeakers or the material to be broadcast may have fewer than five channels. The problem is how best to produce...
Topics: matrix, digital, audio, signal, inputs, hdtv, transputer, analogue, dsp, channel, channel status,...
R&D Report 1980-11 : Colour operation of a solid state sensor telecine. I. Childs An experimental colour film scanner has been constructed using solid state CCD image sensors. Such a scanner should give improved reliability and ease of maintenance together with good picture quality. Various technical aspects of performance are discussed and the picture quality is shown to be in most respects at least as good as that of a flying spot scanner. One possible exception is the noise level, which...
Topics: sensor, sensors, ccd, noise, colour, signal, frequency, sensitivity, spatial, response, light...
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,...
Topics: recording, digital, magnetic, beam, density, thermoplastic, data, film, storage, laser, error rate,...
R&D Report 1954-06 : Assessment of noise in television: Its visibility over the grey scale. D. Maurice The noise characteristics of several different television picture sources are examined and conclusions are reached as to the form of the dependence (or independence) of the noise upon picture signal strength. In some cases the noise is concentrated in the darker regions of the picture whilst in others it is found more in the lighter parts; in yet a third case it is independent of picture...
Topics: noise, sensation, brightness, tube, transmission, characteristic, camera, signal, gamma, film,...
R&D Report 1996-04 : ISO/IEC MPEG-2 AUDIO: Bit-rate-reduced coding for two-channel and multichannel sound. G. Stoll, N.H.C. Gilchrist Since 1988 the ISO/IEC Moving Picture Expertsâ Group (MPEG) has been developing generic coding standards for video and audio, mainly for broadcast and multimedia applications. The MPEG audio standard (ISO/IEC 11172-3) was finalised in November 1992. It follows a three-layer structure in order to fulfil the requirements of various applications. Good audio...
Topics: audio, coding, multichannel, sound, layer, sampling, stereo, digital, frequency, compatibility,...
R&D Report 1956-04 : Absolute measurements in magnetic recording. E.D. Daniel, P.E. Axon. It is shown that an absolute measure of the surface induction of a recorded tape can be made using a non-magnetic conductor of the type developed in Research Department in connection with frequency -characteristic standardisation. Following on this, an analysis of the long-wavelength response of a magnetic recording system is given which leads to a method of defining the absolute sensitivity of a tape...
Topics: tape, sensitivity, recording, induction, flux, reproducing, magnetic, head, recorded, surface,...
R&D Report 1977-21 : Digital video: multiple sub-Nyquist coding. J.H. Stott, G.J. Phillips This Report considers the effect of multiple digital coding of signals, with particular emphasis on sub-Nyquist sampling. Theory is developed which shows that conditions exist whereby no extra degradation due to re-sampling occurs. Experimental work confirming these results is described, and the theory is extended to the use of mixed analogue and digital transmissions, including allowance for...
Topics: filter, sampling, comb, analogue, frequency, coding, digital, response, filters, signal, video...
R&D Report 1960-07 : 'T'-type coaxial notch filters for use at VHF W. Wharton, R.E. Davies This report describes the theory of the "T"-type coaxial notch filter and presents design curves enabling the dimensions of practical filters to be calculated rapidly. the type of filter considered was first described by Sosin and provides a two-terminal impedance with a pole and zero close together in frequency. If the two-terminal impedance is connected in shunt with a transmission line it...
Topics: filter, frequency, notch, coaxial, equations, design, filters, pass, pole, admittance, vision...
R&D Report 1991-03 : A study of sound balances for the hard of hearing C.D. Mathers Over a period of years, complaints have been received from television viewers, especially those who are hard of hearing, that background sound (eg audience laughter, crowd noise, mood music) is often transmitted at too high a level with respect to speech, so that information essential to the understanding of the programme is lost. To consider possible solutions to the problem, a working party was set up...
Topics: hearing, background, subjects, test, tests, intelligibility, speech, bbc, levels, excerpt, hearing...
R&D Report 1996-06 : The Crystal Palace FM filler experiment R.H. Evans, A.J. Bower In some areas of London, listeners to BBC Radio National FM services had suffered from poor reception for some time. The problem was particularly severe immediately south of the River Thames where around one million people suffered with unsatisfactory reception on portable and car receivers. This was due to path blocking of the direct signal from the BBCâs Wrotham transmitter, located several miles south...
Topics: wrotham, crystal, filler, palace, mhz, transmitter, frequency, khz, transmitters, offset, khz...
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 1959-18 : Ring-type transmission-line networks. G.J. Phillips At V.H.F and higher frequencies increasing use is being made of filter networks employing closed rings of transmission line or waveguide. The theory developed here enables them to be related in a simple way to lumped-impedance networks. This not only provides a method of analysing well known arrangements, but is a useful tool in designing new arrangements based on a given lumped-impedance network. The utility of a...
Topics: impedance, impedances, equivalent, terminals, network, networks, lines, circuit, frequency,...
R&D Report 1993-01 : Digital sound: the selection of critical programme material and preparation of recordings for CCIR tests on low bit-rate codecs. N.H.C. Gilchrist A draft new recommendation on low bit-rate digital audio coding for broadcasting is in preparation within CCIR Study Group 10. As part of this work, subjective tests are being conducted to determine the preferred coding systems to be used in the various applications, and at which bit rates they should be used. The BBC has been...
Topics: codecs, audio, material, contribution, broadcasting, digital, recordings, codec, ccir, bbc,...
R&D Report 1990-02 : HDTV -- a chance to enhance television colorimetry. A.Roberts The development of a new High Definition Television system for use within Europe has provided a unique opportunity to depart from standard television colorimetry and coding which has been used worldwide since colour television began. All television systems in operation at present use coding systems which allow substantial proportions of the perceived luminance to travel via narrow band colouring channels,...
Topics: colour, luminance, saturation, hdtv, signals, colours, primaries, mac, gamut, matrix, mac system,...
R&D Report 1987-02 : VHF radio broadcasting: Propagation and diversity reception of mixed polarised signals over a sea path. D.J.Darlington This report describes measurements of VHF propagation over a 170km sea path. Statistical analysis of the results provides information about the correlation between horizontally and vertically polarised field components received from an existing mixed (nominally circularly) polarised VHF transmitting station. The possibility of using a polarisation...
Topics: polarised, signal, polarisation, field, diversity, propagation, component, circularly, reception,...
R&D Report 1986-10 : Development of Slide File -- a digital store for TV stills. M. Weston Slide File is designed to take the place of slide scanners in studios as the prime source of broadcast captions and still pictures. It stores still pictures in electronic digital form and enables them to be selected for transmission by a simple 'cut' or crossfade operation. Such a store provides a convenient means of handling still pictures generated using new electronic techniques as well as handling...
Topics: data, disc, store, pictures, stills, digital, picture, control, computer, input, small pictures,...
R&D Report 1990-03 : Electric field strength meters for the HF, VHF, and UHF bands. R.D.C. Thoday The BBC has been deploying two of its own design of RF hazard meters since about 1964. These are used to ensure that levels of RF field can be measured and thus a safe operating regime can be maintained. The scales on the meters have been modified to reflect new guidance from the National Radiological Protection Board and meters therefore have to be recalibrated. This report describes the...
Topics: meter, calibration, field, strength, frequency, parallel, bbc, meters, tem, electric, strength...
R&D Report 1994-06 : Acoustic noise criteria for listening rooms and control rooms R. Walker This report is based on a submission document to both EBU G1(LIST) and ITU-R TG 10/3 drafting committees. It describes background noise criteria for high-quality listening environments from a number of different organisations and the derivation of a compromise criterion for the continuous background noise levels. The outcome of the work, and the proposal submitted to those technical groups, was the...
Topics: noise, octave, curves, bbc, iso, oirt, rating, criteria, noise rating, curve, listening rooms, band...
R&D Report 1969-20 : A UHF log-periodic receiving aerial J.L. Eaton, R.D.C. Thoday A design of log-periodic UHF receiving aerial has been produced which has substantially constant performance throughout Bands IV and V. The relative levels of side and back lobes do not exceed -24 dB in any channel and the gain is approximately 9 dB (relative to a dipole). Ease of manufacture has been considered as an important feature of design. This type of aerial is particularly suitable for domestic...
Topics: aerial, templet, receiving, radiation, balanced, frequency, dipole, lobes, horizontal, aerials,...
R&D Report 1982-19 : Tests on eight video p.c.m. codecs in tandem handling composite PAL and monochrome video signals. V.G. Devereux The performance of up to eight video pcm codecs in tandem, each employing 8 bits per sample, has been examined by means of subjective tests and objective measurements. In the subjective tests, a sampling frequency of 12 MHz was employed for coding System I (625-line, 5.5 MHz) PAL colour and monochrome video signals. Conclusions are given regarding the minimum...
Topics: codecs, video, frequency, codec, signal, signals, mhz, sampling, quantising, subcarrier, group...
R&D Report 1969-23 : An automatic method for the measurement of reveration-time M.E.B. Moffat, N.F. Spring The automatic measurement of reverberation-time includes the making of a special recording which is characteristic of the studio or other room tested; equipment subsequently selects the required signals from the recording, converts them to digital form and punches a paper tape describing relevant characteristics of the signals. Reverberation-times may then be calculated using suitable...
Topics: reverberation, decay, signal, adc, amplifier, jump, studio, tape, reset, test, logarithmic...
R&D Report 1965-37 : Class-AB amplifiers employing a complementary pair of transistors: Improved method for negative feedback J.B. Izatt This note describes a method of applying current negative feedback to transformerless audio class-AB transistor stages. The output impedance of the circuit is very high but the circuit may also be conveniently adapted to provide a matched output resistance, for example, for a 600-ohm line.
Topics: output, feedback, circuit, current, transistors, transistor, impedance, amplifier, distortion,...
R&D Report 1986-03 : Design of a prototype moving-coil high-frequency loudspeaker drive unit. K.E. Randall A high-frequency loudspeaker drive unit (tweeter) suitable for use in a high-quality studio monitoring loudspeaker is described and the necessary manufacturing information provided. Design considerations are outlined and development problems discussed. Performance is assessed and possible improvements are suggested.
Topics: prototype, tweeter, bbc, khz, harmonic, characteristic, diaphragm, unit, current, design, drive...
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 1966-36 : ST and C microphone Type 4126 (2nd model) H.D. Harwood A brief description of the ST & C Microphone.
Topics: serial, microphone, equalised, unequalised, frequency, specimens, udc, type, report,...
R&D Report 1974-06 : Computer programs for UHF co-channel interference prediction using a terrain data bank R.W. King, J.H. Causebrook A set of computer programs has been written to predict the interference caused by co-channel stations to the service of a television transmitter. These programs use geographical and transmitter information stored permanently on a magnetic drum. In this report an outline is given of the methods employed by the programs. Details are given of the required input...
Topics: data, transmitter, terrain, path, paths, calculation, receiver, profile, iii, field, path profile,...
R&D Report 1966-44 : Programme compressor/limiter using light-controlled variable-loss elements and noise reduction gate. D.E.L. Shorter, R.J. Packer, E.R. Wigan For experiments on the restriction of the dynamic range of programmes, a combined limiter and 2: 1 volume compressor has been constructed. Gain variation is effected in each case by varying the light falling on photo-conductive element; fast-acting solid-state light sources are employed. The equipment, which is transistorized and...
Topics: signal, compressor, limiter, dbm, light, input, circuit, control, photoconductive, output, output...
R&D Report 1956-36 : The Service area of the Les Platons Television Transmitter G.I. Ross, A.R. Williams This report gives the results of field strength survey of the Les Platons television transmitter. The service provided in Jersey is very good. Guernsey, on the whole, has a good service, although a small area in the west of the island receivers a field strength of less than 100 uV/m. Ninety-seven per cent of the population of the Channel Isles is within the 0.1 mV/m field strength...
Topics: les, platons, strength, guernsey, median, jersey, transmitter, field, field strength, channel, les...
R&D Report 1973-13 : MF propagation: A wave-hop method for ionospheric field-strength prediction P. Knight A new method for calculating the strength of medium-frequency sky-wave signals at night is described. Estimated losses due to all the ionospheric and terrestrial factors which affect a wave as it propagates from transmitter to receiver are subtracted from the field strength which would arise if losses were absent. This process is carried out for each propagation mode which is likely to...
Topics: ionospheric, loss, field, paths, strength, reflection, polarisation, propagation, ground, magnetic,...
R&D Report 1994-11 : High frequency room responses : Acoustic design and the control of stereophonic image quality R. Walker Aspects of mid and high frequency acoustic design are described, mainly in the context of relatively small rooms. The factors affecting the design and some of the difficulties which may be encountered are also discussed. The primary means of evaluating the quality of reproduced sound is the studio control room (and its associated equipment). This Report is written...
Topics: acoustic, sound, absorption, frequency, surfaces, reflections, design, reverberation, diffuse, bbc,...
R&D Report 1984-14 : Electronic generation of text for television. N.E. Tanton The image quality of present-day television character generators is compared with the quality of text images derived by scanning real network. To illustrate and identify the causes of image distortion (aliasing) prevalent in these and other synthetic television images, the spectral consequences of scanning a scene and of representing any image with a two-level (1-bit) signal are discussed. A method of...
Topics: image, filter, frequency, vertical, filtering, character, scanned, signal, spatial, electronic,...
R&D Report 1971-36 : Field store standards conversion: Equalisers for ultrasonic quartz delay lines R.V. Harvey A field-store standards converter has been built which uses fused quartz delay lines as the storage medium for the television signal. The associated amplifiers, which have been described elsewhere (BBC RD 1970/24), contain equalisers which allow the gain and group-delay to be adjusted so that the overall delay-unit response lies between very close, specified, limits. The present...
Topics: delay, equaliser, amplitude, equalisation, quartz, amplifier, equalisers, response, output, mhz,...
R&D Report 1980-12 : An investigation into the mechanism of sound-energy absorption in a low-frequency modular absorber. R. Walker, K.E. Randall An investigation into the behaviour of a widely used type of modular, low-frequency acoustic treatment is described. A region of spurious sound-energy absorption in the middle part of the audio frequency range, which was originally acceptable, has become more significant in units made since the prototypes were tested in 1969. This has caused...
Topics: absorption, frequency, coefficient, modular, impedance, reverberation, acoustic, absorber,...
R&D Report 1994-13 : DRACULA: Dynamic range control for broadcasting and other applications. N.H.C. Gilchrist The BBC has developed a digital processor which is capable of reducing the dynamic range of audio in an unobtrusive manner. It is ideally suited to the task of controlling the level of musical programmes. Operating as a self-contained dynamic range controller, the processor is suitable for controlling levels in conventional AM or FM broadcasting, or for applications such as the...
Topics: dynamic, gain, range, digital, signal, controller, compression, audio, processor, broadcasting,...
R&D Report 1971-18 : Selectivity of MF transistor portable receivers M.J. Buckley, J.G. Spencer Abstract Subjective measurements have been made in the laboratory on ten transistor portable receivers of current and recent type to determine their selectivity on the MF band, and the extent to which they might suffer overloading by strong local signals. The investigation covered frequency spacings between the wanted and interfering transmissions of from 9 kHz to approximately 250 kHz. The...
Topics: signal, frequency, receivers, selectivity, wanted, interference, interfering, khz, protection,...
R&D Report 1966-55 : Differential fading of television signals at UHF C.P. Bell When receiving television signals at a translator rely station, for re-transmission after frequency changing, a common amplifier for sound and vision signals is usually employed. Thus the power ratio of the re-transmitted signals is the same as that received from the parent station. Differential fading of the sound and vision signals is therefore important, inasmuch as it would affect this radio. This report...
Topics: fading, vision, receiving, differential, measurements, caversham, sound, aerial, height,...
R&D Report 1995-15 : The effects of frequency errors in OFDM J.H. Stott An OFDM system can suffer from two types of frequency error: firstly, a frequency offset (as might be caused by the tolerance of the local=oscillator (LO) frequency); secondly, an error in the receiver mast clock frequency (which will cause the spacing of the demodulating carriers to differ from those transmitted, and the duration of the receiver integrate-and-dump process to differ from the reciprocal of the...
Topics: carriers, frequency, carrier, error, symbol, offset, ofdm, ici, receiver, variation, demodulating...
R&D Report 1985-18 : Digital video: assessment of comb-filter design for sub-Nyquist PAL codecs. N.D. Wells One very effective technique for the bit-rate reduction of digital PAL signals is sub-Nyquist sampling. This technique requires the use of comb filters which attenuate unwanted alias components produced by the sub-sampling process and also reconstruct the colour signal to standard form at the decoder. Variations are possible in the design of comb filter; in particular, the...
Topics: pal, comb, frequency, signal, digital, chrominance, filter, filters, picture, alias, digital comb,...
R&D Report 1994-17 : Com3: A Composite-Compatible Component coding system G.A. Thomas This Report describes a method for conveying a component video signal on a single cable in such a way that it may be passed through any existing composite studio equipment that has a bandwidth of approximately 9 MHz. The system was originally termed Extended Studio PAL, although it is now referred to as Composite-Compatible Component (Com3, Com cubed) in order to emphasise the quality difference it offers...
Topics: signal, chrominance, luminance, vertical, ntsc, frequency, coded, pal, filter, horizontal,...
R&D Report 1992-13 : Measurement of display transfer characteristics using test pictures. A. Roberts There are three basic parameters which define the transfer characteristic of monitors: contrast, flare and gamma. Each of these can be measured, with varying degrees of accuracy, by a variety of methods. This Report attempts to clarify the definitions of the terms and to specify methods of measurement which give unique and repeatable results. Test pictures are described which permit...
Topics: measurement, flare, test, black, display, measurements, signal, contrast, displays, level, test...
R&D Report 1993-08 : Optimum dimension ratios for studios, control rooms and listening rooms. R. Walker Most control rooms, listening rooms and small studios have dimensions that become comparable with the wavelength of the sound within the normally accepted audio range. Standing waves, where one of the room dimensions is an integer multiple of half the wavelength of the sound energy, result in irregular frequency responses. The response will also be a strong function of position of both...
Topics: room, rooms, criterion, proportions, values, quality, modes, height, mode, bbc, dimension ratios,...
R&D Report 1986-06 : Compatibility of Band II broadcast transmissions at frequencies below 105 MHz with private mobile radio in the band 105-108 MHz. G.H. Millard, R.D.C. Thoday Consideration is given to the problems that may arise with the operation of Private Mobile Radio (PMR) receiving base-stations using the frequency band 105-108 MHz in proximity to broadcast transmitters in Band II. The existing criteria for the protection of the Broadcasting Service from land mobile services and the...
Topics: broadcast, transmitter, mhz, pmr, transmitters, spurious, receiver, frequency, intermodulation,...
R&D Report 1989-02 : The control of the audible effects of ground vibrations in building structures. R. Walker, C.D. Mathers Over a period of about 8 years a number of investigations into the problems of vibration isolation, particularly of large structures, has been carried out, mostly in preparation for the development of a site (The Langham) which is subject to severe vibration interference from London Underground trains. The well-known limitations of some types of commercial vibration...
Topics: vibration, isolation, frequency, acoustic, studio, frequencies, measured, vibrations, resonant,...
R&D Report 1987-01 : A survey of achieved levels of airborne sound insulation in broadcasting studio centres. D.J. Meares A survey has been carried out on results from field measurements over the past fifteen years of the sound insulation of partitions in the technical areas of studio centres. The conduct of that survey is outlined and some examples of the acoustic performance of paritions are given.
Topics: sound, insulation, partition, bbc, average, acoustic, studio, partitions, triple, brick, triple...
R&D Report 1960-16 : Band II receiving aerial for a motor car H. Page, J.A.S. Fox Although the very-high-frequency (vhf) sound service in Band II (87.5 - 95 Mc/S) now provides virtually complete coverage of the United Kingdom, the car receivers in use in this country rarely incorporate a vhf range. This is probably because the medium-frequency (mf) transmitters give reasonably satisfactory reception in a car of all British programmes. The main drawbacks are fading, man-made interference,...
Topics: aerial, horizontal, radiation, ratio, band, height, whip, sensitivity, receiving aerial, reference,...
R&D Report 1972-25 : Loudspeaker distortion associated with low-frequency signals H.D. Harwood Three differing forms of distortion, which are associated with low-frequency signals in loudspeakers, are investigated. It is shown that distortion due to the Doppler effect can be compared with that due to wow and flutter in recording machines and subjective data obtained for this purpose can be applied to loudspeakers. Generalised design limits for loudspeakers are calculated and it is seen that...
Topics: distortion, loudspeaker, frequency, sound, orifice, velocity, doppler, vent, pipe, resonance, sound...
R&D Report 1971-43 : Tropospheric radio wave propagation over irregular terrain: The computation of field strength for UHF broadcasting J.H. Causebrook, B. Davies The report describes techniques for application in a digital computer programme to calculate the field strength of UHF transmitters, with a particular emphasis on the determination of field at long distances which may cause a co-channel interference limitation to a broadcast service. Theoretical calculation methods for certain...
Topics: diffraction, propagation, surface, edge, tropospheric, heights, loss, path, height, field,...
R&D Report 1952-02 : Some experiments on the calibration of velocity microphones at low audio frequencies by motional impedance measurements (Second Report). H.D. Harwood, D.E.L. Shorter Experiments on the low frequency calibration of ribbon type velocity microphone by electrical impedance measurements have been extended to diaphragm type microphone. One of these microphones has been calibrated by this method as a standard of frequency response in the range 40 c/s to 200 c/s and the...
Topics: frequency, ribbon, coil, velocity, motional, impedance, microphones, calibration, response,...
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 1996-11 : Motion estimation for MPEG-2 coding using 'true' vectors G.A.Thomas The motion estimator is a key component of any MPEG-2 video coder. It is common practice to use a method based on block-matching, which generates vectors designed to yield good predictions of images to be coded, without regard for whether the vectors correspond to actual motion. This Report describes a method of deriving motion vectors for an MPEG-2 coder from a motion estimator designed to produce...
Topics: vectors, vector, refinement, field, coding, traced, pixel, tracing, sequences, motion, vectors...
R&D Report 1968-45 : The influence of the ground and the sea on medium-frequency sky-wave propagation P. Knight, R.D.C. Thoday The strength of the low-angle sky waves radiated by a medium-frequency aerial depends on the conductivity of the ground extending for many wavelengths in the direction of propagation. The field strength is greatest if the aerial radiates over open sea from the coast and falls to a limiting value as the distance between the aerial and the sea increases. Measurements...
Topics: ground, aerial, loss, inland, propagation, field, vertical, aerials, sea, strength, vertical...
R&D Report 1955-24 : The Stephens electrostatic microphone Type C-1. D.C. Derham Laboratory tests have been carried out on a single specimen of the Stephens Trusonic Microphone, Type C-1, a pressure-operated electrostatic instrument which functions by amplitude-modulating a radio-frequency carrier. Measurements of frequency response, sensitivity, variation of sensitivity with mains voltage, impedance and susceptibility to interference from magnetic fields have been made; the stray...
Topics: frequency, microphone, stephens, transformer, circuit, demodulator, impedance, electrostatic,...
R&D Report 1963-29 : Relative merits of the VU meter and peak programme meter in the regulation of AF signals in broadcasting. E.R. Wigan The relative merits of the 'V.U. meter' and 'Peak Programme Meter' (P.P.M.) as volume-indicating devices have been hotly if inconclusively contested for many years; this article introduces some points which merit fuller discussion and is based on the experience gained by the BBC in the last decade. The conclusion is confirmed that a quasi-peak reading...
Topics: meter, programme, signal, modulation, transmitter, operator, loudness, transmission, peak,...
R&D Report 1954-37 : NTSC colour television system: Interference on monochrome television receivers by the chrominance subcarrier. L.C. Munn, R.D.A. Maurice The tests described were undertaken during the period in July for which a simulated chrominance signal was radiated from the Alexandra Palace, and, a far as possible, the radiated signal was used for the purpose of the tests. Measurements were made at Kingswood on a group of six domestic television receivers, the main objects being: a....
Topics: subcarrier, chrominance, brightness, receivers, receiver, luminance, dot, raster, sound, signal,...
R&D Report 1964-74 : Visit to Holland and Germany June 1964 R.S.C. Gundry, A. Brown, L.G. Rogers, C.L.S. Gilford A report on a visit to Holland and Germany to discuss recent trends in the broadcasting services and in studio design and equipment.
Topics: studios, studio, stereophonic, insulation, monophonic, acoustic, hanover, reverberation, holland,...
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 1956-37 : Temporal variation of the ground-wave field strength of medium frequency broadcasting transmitters. M. Deakin, E. Sofaer, R.A. Rowden This report surveys the results of measurements made by the BBC Research Department and comments on earlier work by others. It is concluded that the effect, which is due apparently to a variety of factors not yet fully investigated, is no longer of significant importance in broadcasting.
Topics: strength, variation, field, variations, temporal, wave, conductivity, transmitters, signal,...
R&D Report 1962-05: Vertical resolution and line broadening. G.D. Monteath This report is concerned with the effects of scanning in lines on a television picture, and with methods of broadening the scanning lines so as to reduce or eliminate these effects. Scanning is treated theoretically as a sampling process, and the ideal form consideration of polynomial interpolation. A number of methods of line broadening are discussed; two of these enable the profile to attain negative values, so...
Topics: vertical, scanning, profile, lines, spot, horizontal, wobble, broadening, frequency, picture,...
R&D Report 1954-14 : A new programme meter. E.R. Wigan This report looks at the design and making of a new performance meter.
Topics: scale, meter, optical, instrument, mirror, pointer, modulation, standard, frosted, light, programme...
R&D Report 1960-18 : An experimental transistor receiver for VHF sound broadcast reception. R.V. Harvey The report describes the design of an experimental transistor f.m. broadcast receiver. The circuit uses ten transistors which are currently available at moderate cost, and embodies a recently developed type of limiter and discriminator. The performance is equal, in the more important respects, to that of the better quality domestic receiver using valves.
Topics: output, receiver, oscillator, limiter, suppression, discriminator, frequency, signal, transistor,...
R&D Report 1954-32 : The Labor Tube microphone Type MD3 Studio. W.I. Manson, J. Nash The Labour type MD 3 Studio microphone is a moving-coil instrument in which the sound is transmitted to the diaphragm through a telescopic tube several feet long; the microphone is used occasionally for special purposes in television transmissions. Measurements of frequency response, sensitivity, impedance and susceptibility to interference from alternating magnetic fields have been made on a single...
Topics: microphone, frequency, tube, labor, axial, studio, baffle, response, telescopic, impedance, labor...
R&D Report 1961-20 : Visit to Aachen, 25th-29th September, 1961. W.N. Sproson This report details the authors visit to Aachen in September 1961 to attend the ninth annual convention of the German Television Society (Fernseh-Techische Gesellschaft) during which they presented a paper.
Topics: television, described, colour, paper, ntsc, magnetic, vidicon, papers, technique, transmitter,...
R&D Report 1982-02 : L.F. radio-data: specification of BBC experimental transmissions 1982. S.R. Ely, D.T. Wright The BBC long-wave am transmitter network is currently carrying an experimental data signal, in addition to the normal programme signal modulation. The data signal is conveyed by phase-modulation of the carrier, the signal parameters being chosen so that there is no disturbance to reception on existing domestic receivers. This Report describes the experimental data signal and...
Topics: data, block, code, blocks, codes, cyclic, crc, transmitted, bbc, bits, crc word, binary number,...