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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 1978-14 : The use of a programmed computer to perform real-time companding of high-quality sound signals G.W. McNally A small computer has been used to process digital sound signals in real time under the control of a stored program. This has permitted the execution of the processing involved is six companding systems, which are currently under examination for possible use in national and international transmission networks. Thus the subjective performances of the compandors...
Topics: companding, digital, program, nicam, system, signals, signal, bbc, sound, tdf, linearly encoded,...
R&D Report 1965-13 : Transmitting aerials for the Granton VHF television and VHF sound station D.W. Osborne, R.D.C. Thoday The Grantown relay station came onto operation on 8th February 1965. It provides a television and v.h.f sound service to Grantown, Nethy Bridge, Boat of Garten, Carrbridge and Duthil; parts of Aviemore are also served.
Topics: aerial, horizontal, dipole, tiers, gain, templet, transmitting, band, tower, radiation, radiation...
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 1966-68 : Acoustic tests in Dubbing Suite No. 2 Television Centre East Block C.L.S. Gilford, D.K. Jones The second Dubbing Suite, which consists of a Dubbing Theatre and its recording and Mixer Rooms, has recently been completed in the East Block of Television Centre. Measurements of reverberation time, background noise level and sound insulation were made in this Suite of three rooms. Section 2 gives the results obtained and their implications are discussed in Section 3.
Topics: mixer, dubbing, reverberation, theatre, recording, noise, room, insulation, sound, acoustic,...
R&D Report 1991-01 : Interference protection requirements for terrestrial microwave link in the UK private-user frequency bands. P.D. Gill, M.C.D. Maddocks Many broadcast television circuits are carried on microwave links in the private-user frequency bands. At present the television signals are carried in analogue form. High data-capacity links would be required to allow television signals to be carried in digital form. The bandwidth available in the lower frequency private-user bands...
Topics: interference, mhz, offset, spectrum, measured, qpsk, signal, frequency, interfering, calculations,...
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 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 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 1968-52 : A frequency-dependent compandor system for high-quality sound signal distribution D.E.L. Shorter, W.I. Manson Compandors of the type used in telephony for the improvement of signal-to-noise ratio are unsatisfactory for high-quality sound circuits because of the objectionable effect produced by programme-modulated noise. In the case of 'white' noise, this difficulty can be largely overcome by splitting the audio-frequency range into two parts and applying the compandor...
Topics: signal, gain, pilot, tone, frequency, system, limiter, compandor, delay, programme, sending...
R&D Report 1977-12 : LF and MF propagation: a study of sky-wave field-strength variation. P. Knight LF and MF sky-waves vary in strength during periods which may be as short as a minute or as long as 11 years; this range includes day-to-day, diurnal, seasonal and solar-cycle variations. A detailed study has been made of all that is known about LF and MF sky-wave field-strength variation and this has been supplemented by further analysis of measured data.
Topics: variation, measurements, field, propagation, strengths, strength, seasonal, median, frequency,...
R&D Report 1981-01 : Revision of the sound insulation requirements in broadcasting studio centres. R. Walker The BBC sound insulation requirements within studio centres have been based on a report published in 1968. Since that time, there have been new measurements of sound pressure levels in studios, control rooms and other areas, and new background noise level criteria have been proposed for programme areas. Both of these factors affect the amount of sound insulation which is necessary to...
Topics: insulation, sound, noise, studio, criteria, frequency, pressure, level, criterion, background,...
R&D Report 1977-29 : The HMI 575-watt metal-halide discharge lamp: measurements and predicted effects of intensity ripple using sinusoidal lamp excitation. E.W. Taylor A description is given of measurements of the light intensity ripple characteristics shown by the Wotan HMI 575-watt metal-halide discharge lamp as manufactured by Osram BmbH, Germany, when excited from a sinusoidal power source at various frequencies in the range 50Hz-2KHz. Operating conditions which reduce motion picture...
Topics: ripple, lamp, frequency, supply, shutter, camera, ratio, iii, intensity, dissipated, shutter...
R&D Report 1963-37 : Accelerometer pickup as a diagnostic tool in noise studies in buildings F.L. Ward In this report are discussed the ways in which a pizeo-electric accelerometer pick-up can be of value in noise studios and associated buildings. Five cases are described briefly as examples. The report is based on a paper presented at the Fourth International Congress Acoustics held at Copenhagen from 21st to 28th August 1962. It contains some material which, although presented in the...
Topics: accelerometer, vibration, transmission, measurements, measurement, source, sound, studio, levels,...
R&D Report 1966-49 : Acoustic tests in the new headquarters, Wales (Baynton House, Cardiff) D.K. Jones. This report gives the results of a series of preliminary acoustic tests in the sound studios, cubicles and recording rooms at the BBC's news Headquarters, Wales. None of the studios was complete; no fabric covers were fitted to the acoustic treatment nor were carpets laid. It is shown that changes in building methods may have serious acoustic consequences unless a close check is...
Topics: studio, reverberation, cubicle, insulation, decay, measurements, studios, noise, recording,...
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R&D Report 1956-38 : Low-power V.H.F./F/M. transmitters - Galashiels area site tests. C.J. White, D.W. Taplin, R.S. Sandell, J. Hall Two sites were tested in the Galashiels area. It was found that Lindean Moor would provide the better service and this site is therefore recommended. Tests on the reception of television sound indicated the probability of a reliable signal from the Kirk o' Shotts v.h.f. transmissions for rebroadcasting from Lindean Moor.
Topics: lindean, strength, moor, shotts, dryden, site, aerial, field, transmitter, kirk, television sound,...
R&D Report 1954-09 : Information on short wave propagation conditions from reception results on fixed frequencies. T.W. Bennington Regular hourly observations made at Panorama, South Africa, on reception of five fixed frequencies from Standard Frequency Station WWV have been analysed to obtain information on propagation conditions and their daily and seasonal variations, for comparison with those given by world charts of predicted MUF. The results indicate that the predications agree well...
Topics: reception, muf, frequencies, gmt, propagation, signal, frequency, predicted, luf, panorama, sinpo...
R&D Report 1979-16 : Digital recording using hologram arrays: development of the transducers for an experimental 100 Mbit/s recorder. K. Hacking, J.L. Riley Three special transducers for use with an experimental holographic recorder have been partly developed. They are a hologram page-composer with 50 ports, a solid-state digital light-deflector and a photodetector array for intercepting 100 light beams. The page-composer is based on an electro-optic ceramic material, PLZT, in the form of a...
Topics: plzt, optical, hologram, deflector, array, modulator, digital, switching, electrode, output,...
R&D Report 1972-40 : Pulse-code modulation for high-quality sound-signal distribution: Subjective effect of digit errors G.R. Mitchell, M.E.B. Moffat In a companion report (Report No 1972/18) a digit-error-protection technique was recommended for use in a multiplex pulse-code modulation (PCM) system for high-quality sound-signal distribution. The technique is briefly summarised in the present report. Tests have been carried out with and without the application of the protection technique to...
Topics: error, impairment, test, probability, tests, errors, grade, subjective, programme, intelligibility,...
R&D Report 1984-08 : A transportable satellite earth station. M.W. Harman, C. Gandy The report describes the main factors that were taken into account in establishing the design of a transportable transmitting earth station for relaying television signals via a satellite. The realisation of a practical system to work with the Orbital Test Satellite (OTS) and the European Communications Satellite (ECS) is outlined together with details of the link power budget and results of the performance...
Topics: satellite, transportable, antenna, ots, bbc, earth, transponder, terminal, ecs, equipment, power...
R&D Report 1996-02 : MPEG-2: Overview of the systems layer P.A. Sarginson The MPEG-2 Systems specification describes how MPEG-compressed video and audio data streams may be multiplexed together with other data to form a single data stream suitable for digital transmission or storage. This Report introduces the principles and terminology of the MPEG-2 Systems layer. The Report covers three main areas: Firstly, the structure of the multiplexes; secondly, the service information that may be...
Topics: elementary, stream, buffer, coder, programme, access, transport, decoder, video, streams,...
R&D Report 1969-52 : A p.c.m. sound-in-syncs distribution system: combination and separation of sound and video signals C.J. Dalton This report, one of a series of four, gives the basic requirements and simple descriptions of experimental equipment for the combination and separation of sound and video signals as used in the 'sound-in-syncs' system for conveying a sound signal together with a video signal along a video link. Performance figures for the equipment are given and from the...
Topics: sound, pulse, signal, video, separator, detection, pulses, sync, separation, distribution, sound...
R&D Report 1982-03 : Radio-frequency ignition hazards: the power available from non-resonant structures. P. Knight Structures in petrochemical and similar industrial plants can act as inadvertent receiving aerials, leading to a risk of ignition of flammable vapours when strong radio waves are present. The hazard is greatest when the structure is tuned to the transmission frequency. When several transmissions are present, the structure is unlikely to be tuned to more than one transmission at...
Topics: voltage, tuned, frequency, curves, power, crane, structures, structure, transmission, impedance,...
R&D Report 1996-12 : Mobile Broadband System. A report on the work of RACE Project 2067. J.T. Zubrzycki Mobile Broadband System (MBS) is a wireless cellular radio network capable of carrying digital signals at bit rates sufficient for digital video, including compressed HDTV. The technological feasibility has been studied in RACE* Project 2067 MBS, which had the aim to extend the Broadband Integrated Services Digital Network (B-ISDN) to mobile users, providing much higher capacity to users...
Topics: mbs, mobile, ghz, base, broadband, demonstrator, antennas, antenna, project, diversity, diversity...
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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 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 1966-26 : Tristimulus spot colorimeter. H.A.S. Philippart The report describes a photoelectric tristimulus spot colorimeter which measures the three stimuli X, Y, Z, as specified by the C.I.F. (Commission Internationale de l'Eclairage) standard observer, and thus permits simple calculation of the x and y trichromatic coefficients (chromaticity co-ordinates). In addition to the usual measurements of the colours of materials, the instrument permits measurements of the colours...
Topics: filters, instrument, tristimulus, colour, wavelength, filter, spectral, colorimeter,...
R&D Report 1965-10 : Transmitting aerials for the Carmarthen VHF television and VHF sound station D.W. Osborne, R.D.C. Thoday The Carmarthen relay station came into operation on 15th March 1965. It provides a television and v.h.f sound service to Carmarthen and Abergwili.
Topics: transmitting, tower, band, dipole, horizontal, gain, carmarthen, aerial, aerials, templet,...
R&D Report 1963-56 : Performance of certain television receivers designed for the 525/60 standard when operated from a 50 c/s mains supply. G.C. Wilkinson This report describes subjective tests on the performance of three domestic receivers, all designed to operate from either 50 or 60 c/s power supplies while displaying 525-line, 60 field-per-second television pictures; the tests and measurements were based upon techniques described previously. The test results show that, when operating...
Topics: receiver, receivers, picture, wobble, flicker, subjective, supply, mains, displayed, television,...
R&D Report 1972-01 : A medium-wave field-strength measuring review D.E. Susans, R.D.C. Thoday, M.J. Buckley This report describes a field-strength measuring system for the frequency range 510-1610 kHz. It incorporates a commercially available receiver, with some modifications. The loop aerial used with this receiver is mounted on the roof of a Commer 2000 metal-bodied vehicle. The calibration arrangement, using a specially constructed unit with an oscillator, permits the receiver to give...
Topics: calibration, loop, receiver, tuning, attenuator, output, amplifier, oscillator, aerial, vehicle,...
R&D Report 1971-23 : Colour film telerecording using a shadow-mask display tube J.D. Lunn The development of shadow-mask tubes with increased luminance has justified an investigation into the feasibility of using such a display in colour-film telerecording equipment. This would represent a considerable simplification over an earlier colour telerecording proposal in which a system of dichroic mirrors superimposed the displays from three separate cathode ray tubes, each carrying a single...
Topics: phosphor, display, luminance, telerecording, matrix, spectral, phosphors, film, colour, luminances,...
R&D Report 1980-04 : Enhanced UK Teletext moves towards still pictures. J.P.Chambers The UK teletext specification includes several provisions for future enhancement of the system while retaining its basic ruggedness and efficiency. By means of an example of a possible specification of an enhanced UK teletext system, this Report draws attention to the immediate benefits that could be provided. It indicates how later extensions up to and including the broadcasting of high-quality still...
Topics: teletext, character, display, characters, row, mode, data, mosaic, codes, control, character codes,...
R&D Report 1954-01 : The service area of the temporary television transmitters at Truleigh Hill, Pontop Pike and Glencairn. G.I. Ross This report gives the results of a survey of the service areas of the temporary low power transmitters at Trueleigh Hill, Pontop Pike and Glencairn. Tests in the service area of the Glencairn transmitter revealed that echo effects (ghosts) are not serious and are readily eliminated. Reference is made to the deterioration in the service that may expected when...
Topics: pontop, truleigh, strength, pike, temporary, transmitters, transmitter, field, field strength,...
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 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 1960-10 : The range of colours excited by a two-colour reproduction system. W.N. Sproson Some experiments are described in which two-colour and three-colour reproductions of the same scene are compared. Optical projection of the separation positives was used in the main but a description of a colour television demonstration is also given. The accuracy of a two-colour process is assessed on the basis of the colour names given to specified areas of the colour reproduction in the...
Topics: colour, colours, green, brown, separation, identical, blue, namings, brown brown, observers, grey...
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R&D Report 1955-08 : The Robbins-Joseph (R-J) loudspeaker enclosure. D.E.L. Shorter, H.D. Harwood, R.J. Packer Tests have been carried out on a small loudspeaker cabinet known as the "R-J enclosure" which has been claimed to give improved bass reproduction. A small increase in efficiency at low frequencies resulting from the particular form of construction adopted is accompanied by some reduction of response in other parts of the frequency range.
Topics: enclosure, response, loudspeaker, frequency, vent, impedance, enclosures, cone, axial, frequencies,...
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 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 1964-16 : UHF amplifier and distribution unit D.E. Susans This report describes a simple single-transistor u.h.f. amplifier suitable for use either as a low noise pre-amplifier for a receiver or as a mast-head amplifier remote from the receiver. The amplifier, with a gain of 12 dB, can be made for use at any single Band IV and V television channel. A bridge distribution unit is also described which enables the output of the amplifier or other u.h.f. source to be split into four...
Topics: amplifier, distribution, input, bridge, transistor, unit, output, circuit, outlets, cable,...
R&D Report 1972-13 : The performance of a non-synchronous AM detector designed to remove asymmetric-sideband distortion N.H.C. Gilchrist Asymmetry between the upper side-band and the lower side-band of an amplitude-modulated signal gives rise to distortion of the signal in receivers employing envelope detectors. The use of a synchronous detector removes the problem of asymmetric-sideband distortion. An alternative, non-synchronous, detector has been developed which could replace the...
Topics: detector, carrier, enhancement, modulation, khz, distortion, signal, envelope, sideband, grade,...
R&D Report 1973-18 : The automatic plotting of aerial radiation patterns G.H. Millard, N.F. Spring The presentation of aerial radiation patterns in the form of contour plots is described and a brief account is given of the plotting algorithm.
Topics: radiation, contours, bbc, pattern, aerial, horizontal, plotting, contour, patterns, diagram, beam...
R&D Report 1978-09 : A digital telecine processing channel. A. Oliphant An experimental digital telecine processing channel is described. It performs the operations of gamma correction, colour masking and aperture correction. To give sufficient coding resolution in the green channel a dual-range ADC has been developed which gives 11-bit resolution for small signals. The problem of Moire patterns arising from aliasing caused by non-linear processing have been investigated and found to be...
Topics: digital, signal, sampling, frequency, dither, adc, gamma, channel, input, quantising, quantising...
R&D Report 1982-12 : High quality decoding for PAL inputs to digital YUV studios. C.K.P. Clarke With the planned conversion of studio equipment to digital component signal operation, there will be a requirement for high quality PAL decoders at the interface with current equipment. The addition of movement detection circuits to picture delay comb filters was expected to produce a decoder with good overall performance. However, movement detection methods have so far been unable to produce a...
Topics: chrominance, luminance, decoding, yuv, frequency, digital, signals, pal, movement, comb, yuv...
R&D Report 1992-09 : Low-frequency room responses: Part 2 -- Calculation methods and experimental results. R. Walker The development of a relatively simple method for predicting low- frequency responses for near-rectangular rooms based on the summation of modal responses and their coupling coefficients for the source and receiver positions is outlined. Comparisons between calculated and measured responses show that many of the response features can be reproduced. The question of optimum...
Topics: room, frequency, loudspeaker, frequencies, loudspeakers, octave, measured, mode, modes, response,...
R&D Report 1966-28 : The design of a low-frequency unit for monitoring loudspeakers. H.D. Harwood The present state in the design of low-frequency loudspeaker units is reviewed and the areas where improvement is desired are indicated. Experimental details are given leading to the design of 12 in. (305 mm) unit incorporating a vacuum-formed cone of toughened polystyrene with a p.v.c. (poly-vinyl chloride) surround and it is shown by objective and by listening tests that this design is...
Topics: cone, frequency, surround, mould, unit, shape, characteristic, axial, goodmans, loudspeakers,...
R&D Report 1966-63 : Colour errors in the telecine reproduction of Technicolour film C.B.B. Wood, E.W. Taylor, F.A. Griffiths Some colour films show incorrect colour in dark areas of the picture when reproduced by colour telecine. The cause of this error is discussed and a remedy, involving an alteration to the red colour-analysis characteristic, is described.
Topics: technicolor, colour, film, eastman, channel, density, dye, telecine, red channel, output, film...
R&D Report 1968-58 : Ray tracing for ionospheric and tropospheric propagation studies K. Hacking Adapted for a digital computer, conventional ray tracing becomes a potentially useful technique for studying several aspects of long-range wave propagation through stratified media. The development of a ray tracing program and its application to both medium-frequency sky-wave propagation through the ionosphere and ultra-high-frequency (UHF) propagation in the troposphere are described in this...
Topics: ray, propagation, height, trajectory, equation, ionospheric, absorption, refractive, range, angle,...
R&D Report 1987-17 : Experimental radio data system (RDS): A survey of reception reliability in the UK. A.G. Lyner The report describes a field survey which was made to investigate the reliability of reception of the Radio Data System (RDS). Trade-test transmissions of RDS were introduced on all BBC Band II VHF/FM radio signals broadcast in England in August 1987. A full public service of RDS is expected to commence in England in mid-1988. The survey covered both mobile (car) and static...
Topics: rds, reception, codes, survey, multipath, receiver, received, grade, bbc, code, khz injection,...
R&D Report 1986-08 : The measurement of large values of airborne sound insulation. R.Walker The requirements for and the measurement of airborne sound insulation between areas in a broadcasting centre are discussed. In particular, the high values of insulation required in some cases and the difficulties of measurement are described. One method which has been used for such measurements, using explosive charges, has been investigated in detail. Some of the results obtained in the past using...
Topics: sound, measurement, insulation, signal, level, noise, frequency, pressure, overload, acoustic, peak...
R&D Report 1994-03 : Measurements of wideband multipath propagation at 531MHz and 1.265GHz C.P. Bell, P.J. Brightwell, P.J. Brightwell, R.F. Rudd, W.F. Williams Multipath propagation measurements and their analyses are described. The work was carried out by the BBC over the period 1988 - 1990 as a contribution to the Eureka 147 Project, with the aim of providing statistical data required in the configuration of a Digital Audio Broadcast system. Two different areas were chosen for the tests,...
Topics: mhz, delay, bbc, measurements, croydon, urban, ghz, multipath, frequency, propagation, correlation...
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 1966-32 : Sennheiser MKH 404 and AKG 628 microphones. H.D. Harwood Two new capacitor microphones, the Sennheiser type MKH 404 and the Akustische und Kino Gerate type 628, have been produced which employ transistor circuits and radio-frequency polarizing of the capsule; both have a cardioid directional characteristic and are of the end-fire type. Measurements of the frequency characteristics have been carried out for sound incident at various angles; the degree of self-generated...
Topics: mkh, type, sennheiser, akg, impedance, frequency, noise, microphone, microphones, circuit, akg...
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...
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 1966-59 : Band III transmitting aerial for the Moel-y-Parc VHF television station D.W. Osborne, R.D.C. Thoday The Moel-y-Parc relay station came into operation on the 28th October 1965. It provides a service to an area including most of the north coast of Wales and to Denbigh, Wrexham and Ruthin to the south.
Topics: panel, aerial, bbc, panels, facing, mounted, transmitting, mast, feeder, feeders, transmitting...
R&D Report 1967-02 : Reports on acoustic tests in studios 1967 A.N. Burd, D.K. Jones Acoustic tests were carried out to investigate interference by noise of footsteps with programmes originating in Mixer Suite 1A. The measurements showed that such interference may be reduced to an acceptable level by the use of resilient covers on the floors of adjacent corridors, staircases and offices.
Topics: mixer, amplitudes, accelerometer, hammer, blows, continuity, studio, position, acceptable,...
R&D Report 1971-11 : Variation of medium-frequency sky-wave field strength with solar activity in Europe J.O. Drewery, P. Knight Abstract Medium-frequency sky-wave field strengths measured late at night during the solar cycle have been analysed. The reduction in field strength due to solar activity has been found to depend significantly on the distance between transmitter and receiver. A modified field-strength correction based on sunspot number and distance is proposed.
Topics: regression, sunspot, solar, strength, activity, distance, variation, field, coefficient,...
R&D Report 1990-04 : Electromagnetic field exposure in broadcast environments. S. Wakeling Recently there has been renewed concern over possible deleterious health effects from exposure to electromagnetic fields. In the light of increasing evidence of detectable biological 'effects', international authorities have been recommending more stringent exposure levels. As a consequence, the areas around broadcast antennas to which a person can safely gain access are becoming increasingly...
Topics: exposure, field, electromagnetic, effects, strengths, nrpb, magnetic, sar, biological, fields,...
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 1956-18 : Measurements on loaded building-board panel sound absorbers. A.N. Burd. Measurements have been made of the absorption coefficient of resonant absorbers consisting of soft building-board panels loaded with steel weights. The results do not substantiate the claims made by Continental workers because the mode of action appears to be completely different from that postulated in a recent paper. A possible explanation of the experimental results is suggested and some measure...
Topics: panel, absorption, frequency, absorbers, reverberation, stiffness, measurements, resonance, peak,...
R&D Report 1967-23 : Transmitting aerials for the Northampton VHF television and VHF sound station D.W. Osborne, R.D.C. Thoday, J.P. Crean The Northampton relay station came into operation on 26th September 1966. It provides a television and v.h.f. sound service to the town of Northampton and the villages of Weston Favell, Duston and Hardingstone.
Topics: aerial, transmitting, tiers, band, yagis, pid, aerials, etn, templet, tower, horizontal radiation,...
R&D Report 1980-13 : The general design of a digital stills-storage system for use with an electronic rostrum colour camera. M.G. Croll The design of a television stills-storage system is described which, in conjunction with an electronic rostrum camera, will generate television sequences including animation effects. Thus, the use of photographic film can be avoided in preparing such sequences for television. The system uses a computer-type disc-pack to store digitised colour television...
Topics: pal, luminance, picture, output, television, vertical, decoder, system, electronic, rostrum, output...
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 1965-24 : Relative visibilities of spatial variations in luminance and chromaticity. K. Hacking An optical method of producing sinusoidal (spatial) variations of the colour of an illuminated screen is described. Either colour variations of chromaticity at constant luminance or colour variations of luminance at constant chromaticity can be selected. An observer viewing the screen can control the magnitude of the colour variation - and hence its visibility. By making...
Topics: luminance, colour, chromaticity, variations, viewing, grating, test, sensitivity, ratio, variation,...
R&D Report 1957-06 : Low-power V.H.F./F.M. transmitters site tests at corwen (Cyrn-y-Brain). C.J. White, D.W. Taplin, R.S. Sandell, J. Hall This report gives the results of an f.m. transmitter site test at Corwen (Cynn-y-brian). It is shown that a low-power transmitter will provide a satisfactory service for most of the population of Denbighshire and Flintshire. The service area would not extend to Anglesey and north-west Wales and another site would be necessary for this area.
Topics: corwen, transmitters, median, site, aerial, transmitter, field, strength, omnidirectional,...
R&D Report 1966-46 : Long-distance tropospheric propagation measurements over the North Sea at 774 MHz. J.W. Stark, C.P. Bell This report presents the results of field strength measurements on horizontally polarized u.h.f. transmissions at 774 MHz over North Sea at distances from 198 km to 950 km. These measurements extended over a period of 2 1/4 years and have been used in the preparation of curves showing field strength as a function of distance for specified percentages of the total...
Topics: measurements, mhz, curves, band, propagation, ccir, strength, field, values, receiving,...
R&D Report 1971-27 : A theoretical model of a colour television display for the assessment of random noise E.W. Taylor A mathematical model of a colour television display is developed, by means of which the subjective visibility of noise in the display may be computed from a knowledge of the noise-signal components at the three video-signal inputs to the display.
Topics: noise, signals, signal, magnitude, colour, luminance, circuit, display, visibility, equation,...
R&D Report 1982-17 : The introduction of mixed polarization for VHF sound broadcasting: the Wrotham installation. G.H. Millard The considerations that led to the decision to change the polarization of the VHF/FM radio network transmitters from horizontal to mixed are discussed. The installation at Wrotham, the first high-power station to be changed to the new standard, is described and its performance given.
Topics: antenna, polarization, horizontal, wrotham, radiation, bbc, component, vertical, phase, mhz, slant...
R&D Report 1996-03 : MPEG video coding: A basic tutorial introduction S.R. Ely MPEG has been outstandingly successful in defining standards for video compression coding, serving a wide range of applications, bit-rates, qualities and services on a worldwide basis. The standards are based upon a flexible toolkit of techniques for bit-rate reduction. MPEG video coding uses a combination of motion-compensated interframe prediction (for reducing temporal redundancy) with Discrete Cosine...
Topics: prediction, dct, coding, picture, macroblock, coded, quantisation, mpeg, frame, coder, video...
R&D Report 1955-17 : Receiver signal/noise ratio improvement using post detector selectivity. R.V. Harvey In the design of radio receivers for the measurement of certain types of amplitude-modulated transmission, a useful increase in the output signal/noise ratio can be achieved by restricting the bandwidth after detection. Even when the signal is well below noise level at the detector input, it may be considerably above noise level at the output of the receiver. The effective gain of the...
Topics: output, signal, detector, ratio, receiver, bandwidth, input, noise, attenuator, modulated, noise...
R&D Report 1966-04 : Acoustic tests on the Walker Memorial Hall, Birmingham. C.L.S. Gilford, T.J.B. Smith Acoustic tests carried out before and after modifications to the Walker Memorial Hall, Birmingham are described. Floor resonances which caused unacceptable musical quality satisfactorily removed.
Topics: reverberation, measurements, floor, studio, decay, accelerometer, cubicle, acoustic, resonances,...
R&D Report 1964-23 : Low noise amplifiers for UHF reception R.V. Harvey, J.B. Izatt, P.C.J. Hill Noise in broadcast receivers generally increase as the frequency increases, whereas noise from external sources decreases. In receivers designed for u.h.f. using conventional valve or transistor circuits, the noise is about 10 dB greater than the aerial noise. There is therefore an obvious economic advantage to be gained by reducing receiver noise at u.h.f., particularly for special purposes...
Topics: amplifier, frequency, noise, diode, idler, circuit, parametric, signal, pump, gain, negative...
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 1964-38 : Transistorized EHT supply for multiplier photo-cells H.A.S. Philippart Multiplier photo-cells normally require a high tension supply of the order of 1000 volts. This supply is usually obtained from the electricity supply mains by means of conventional rectifiers and stabilizing circuits. Mains surges can still be detected however unless more complex and bulky equipment is used. In the case of a fixed installation this is not a great importance but when portability and...
Topics: output, voltage, transistorized, converter, zener, performance, multiplier, supply, technological,...
R&D Report 1964-15 : UHF Harmonic radiation from VHF tuners in television receivers G. Edmondson The local oscillator of a v.h.f. television receiver tends to radiate energy at harmonics of the fundamental oscillator frequency. Some of these harmonics fall within the u.h.f. Bands IV and V and may, therefore, interfere with the reception of u.h.f. television transmissions. The radiation oscillator harmonics of several v.h.f. television receivers has been measured, and the results obtained...
Topics: receiver, radiation, interfering, oscillator, receivers, harmonics, aerial, harmonic, signal,...