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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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BBC Research and Development Reports
by W.I. Manson, D.E.L. Shorter, H.D. Harwood, J. Nash, R.J. Packer
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R&D Report 1954-40 : The Telefunken microphones Type Elam 200 and Elam 201. W.I. Manson, D.E.L. Shorter, H.D. Harwood, J. Nash, R.J. Packer Tests have been carried out on specimens of the Telefunken electrostatic microphones type ELAM 200 and ELAM 201. The ELAM 200 microphone is pressure-operated while the ELAM 201 can be switched to give either omnidirectional or cardioid characteristics; identical pre-amplifier arrangements are used for both types. The usual measurements of frequency...
Topics: elam, blam, microphones, sensitivity, microphone, omnidirectional, cardioid, frequency,...
R&D Report 1988-15 : Implementation of amplitude modulation companding in the BBC MF national networks. C.P. Bell, W.I. Manson, W.F. Williams, et al The introduction of new transmitter designs in the LF, MF and HF broadcast bands has not only improved efficiency directly, but permitted use of modulation-dependent control system which can themselves further reduce operating costs without loss of coverage. This report describes the design and development of one such modulation-controlled...
Topics: amc, modulation, transmitter, transmitters, tests, carrier, signal, compression, brookmans, agc,...
R&D Report 1959-08 : Low-signal amplifying valves for use at U.H.F. R.G. Manton The object of this report is to review some of the types of valve that are suitable for use in u.h.f. amplifying stages in receivers, and to describe units which have been constructed to test the performance of two of these valves at a frequency of about 655 Mc/s.
Topics: amplifier, valve, output, input, amplifiers, anode, bandwidth, grid, gain, impedance, electrical...
R&D Report 1975-04 : Digital video: Sub-Nyquist sampling of PAL colour signals. V.G. Devereux A simple method of applying sub-Nyquist sampling techniques to digital coding of PAL colour video signals is described. This technique employs a sampling frequency of twice the colour subcarrier frequency, the sampling instants being maintained at a specified phase relative to the reference subcarrier. For System I (625-line, PAL) video signals the resulting sampling frequency is about 8.87 MHz....
Topics: sampling, frequency, signal, components, filter, signals, comb, pal, video, subcarrier, pal video,...
R&D Report 1973-01 : Digital video: Effect of PAL decoder alignment on the acceptable limits for timing jitter. V.G. Devereux, G.C. Wilkinson Tests have been performed to investigate the effect of alignment errors in PAL decoders on the acceptable limits for timing jitter in the decoded samples from a pulse modulation (PCM) system carrying 625-line PAL colour television signals. It is shown that certain alignment errors in the PAL decoder such as incorrect adjustment of the static phase of...
Topics: jitter, phase, impairment, pal, amplitude, timing, frequency, static, alignment, subcarrier,...
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,...
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R&D Report 1956-19 : Low power television transmitters -- Rosemarkie. C.J. White, D.W. Taplin, R.S. Sandell, J. Hall This report gives the results of tests at the site selected for a television transmitter at Rosemarkie, near Inverness. It is shown that a low power transmitter at Rosemarkie will provide most of the population in the Dornoch and Moray Firth areas with a satisfactory television service. Reception tests show that the Meldrum television transmission should provide a...
Topics: aerial, meldrum, rosemarkie, television, strength, site, field, transmitter, dornoch, median,...
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,...
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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 1992-11 : A modular wideband sound absorber G.D. Plumb The absorption coefficients were measured of various depths of RW2 grade Rockwool laid directly on the floor of the ISO-Standard reverberation room at BBC Research Department. The Rockwool was very effective as a wideband sound absorber. A new absorber was designed and tested, having the dimensions of existing BBC type A modular absorbers and containing RW2 Rockwool. The new absorber has a smoother absorption coefficient...
Topics: absorption, absorber, rockwool, infill, hardboard, plywood, modular, coefficient, absorbers, panel,...
R&D Report 1955-23 : Analysis of data from subjective tests employing graded scales of observer preference. E.R. Wigan This report deals with the statistical analysis of questionnaires in which observers enter their opinions under a series of graded classification, such as "Bad", "Indifferent", "Good". It is shown that the significance of the opinions expressed can be put into simple and realistic terms. The technique is demonstrated by applying it to the...
Topics: median, data, limits, preference, observers, graded, grading, reliability, deviate, fading,...
R&D Report 1974-17 : The generation of video synchronising pulses and test waveforms by digital synthesis: Timing errors caused by quantising distortion P.A. Ratcliff Digital waveform-synthesis produces interval timing errors, or wave-shape distortion, when generation of transitions is required at intervals which are not integer multiples of the sampling clock period. A rule has been evolved to determine the timing accuracy with which a digital system, with quantisation limitations, is...
Topics: waveform, digital, pulse, synchronising, timing, analogue, pulses, sampling, jitter, waveforms,...
R&D Report 1979-12 : Channel Islands television programme links: the design of a u.h.f. feed antenna for a 9.14 m diameter paraboloidal reflector. G.H. Millard The design of a feed antenna for a paraboloidal reflector is discussed in relation to the optimization of the gain and the likely side-lobe level. The design has been realized in a practical feed antenna but the performance of the complete antenna has not yet been assessed experimentally.
Topics: antenna, feed, reflector, radiation, aperture, paraboloidal, gain, efficiency, illumination,...
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 1974-09 : Subjective study of two large music studios W.N. Sproson Users of two BBC large music studios (Maida Vale 1 and Glasgow 1) were asked to give their opinions on various acoustic characteristics of these studios using a specially devised questionnaire. Three statistical methods of analysing the raw data were used and the results obtained are outlined in this report. One aspect of the work concerns users' views on what would constitute an 'ideal' music studio and these are...
Topics: studio, maida, vale, variables, analysis, tone, coefficient, characteristics, timbre, ensemble,...
R&D Report 1976-35 : Some considerations on the use of pre-amplifiers at low-power UHF relay stations. J.L. Riley A number of inexpensive, commercially available pre-amplifiers are examined and their performances in respect of gain, noise factor, linearity and impedance match are compared. Some theoretical planning curves are presented for considering low-field conditions and formulae are derived for dealing with high-signal conditions. A re-broadcast link front-end, made up from the most...
Topics: amplifier, input, aerial, output, isolation, amplifiers, signal, noise, receiving, feeder, received...
R&D Report 1994-12 : A wideband absorber for television studios. M.D.M. Baird The acoustic treatment in BBC television studios has taken various forms to date, all of which have been relatively expensive, some of which provide inadequate absorption. An investigation has been conducted into the possibilities of producing a new type of wideband absorber which, would be more economic, also taking installation time into account, than earlier designs. This Report describes the absorption...
Topics: absorption, absorber, wideband, frequency, acoustic, mineral, bbc, zintec, weldmesh, absorbers,...
R&D Report 1973-24 : A UHF ruggedised log-periodic aerial J.L. Riley A ruggedised UHF log-periodic aerial covering Bands IV and V and suitable for both receiving and transmitting purposes has been developed. There are two versions of the aerial, one with an air-spaced main feeder boom and the other with a dielectric loading on the aerial boom. Some of the more important design factors are described in detail. The side- and back-lobe radiation is more than 23 dB down on the main lobe at all...
Topics: aerial, boom, radiation, impedance, dipole, mhz, elements, feeder, frequency, aerials, input...
R&D Report 1977-19 : Film lighting using metal-halide lamps: some operating conditions giving freedom from picture luminance fluctuations. E.W. Taylor Film and display parameters required to specify the operating conditions and describe exposure variation and luminance fluctuation effects are defined. Theoretical relationships between camera frame frequency and shutter angle, and lamp supply frequency and intensity ripple characteristics, such that picture luminance fluctuations due to the...
Topics: ripple, frequency, asymmetry, luminance, exposure, supply, camera, lamp, fluctuation, charts,...
R&D Report 1954-24 : Television receivers operating from non-synchronous power supplies. L.C. Munn The tests described in this report were undertaken in order to determine the subjective effects of operating a television service without the normal mains lock by which the frame frequency of a television system is related to the frequency of the power supply. The two major picture disturbances may be termed 'raster wobble' and intensity variation. In these tests all the observers exhibited a...
Topics: frequency, receivers, raster, observers, critical, tolerable, perceptible, intensity, wobble,...
R&D Report 1957-10 : Some experiments on the subjective effect of limiting the upper frequency range of programmes D.E.L. Shorter, W.I. Manson, E.R. Wigan To obtain first-hand knowledge of the subjective effects of high-frequency band limitation, some tests have been carried out with Research Department staff of various categories as observers (thirty-four in all), using twelve types or recorded programme material. Low-pass filters having nominal cut-off frequencies of 10 kc/s and 12 kc/s...
Topics: observers, filter, frequency, observer, programme, experiments, filters, band, material,...
R&D Report 1956-03 : The Ronette crystal microphone cartridge Type MC.65. W.I. Manson, D.E.L. Shorter The report gives tests results on three samples of the Ronette diaphragm-type crystal microphone cartridge MC.65. The performance varies considerably between individual specimens but is on the average superior to that of earlier microphone of this kind.
Topics: microphone, ronette, frequency, crystal, cartridge, specimens, response, specimen, axial, noise,...
R&D Report 1963-20 : Photo-electric lens-testing bench. W.N. Sproson, K. Hacking A photo-electric lens test bench capable of measuring lenses of focal length from 12 mm to 1 m is described. Designed specifically for television applications, it gives the 'optical transfer" curve automatically plotted on recording paper, using the sine-wave analyser described by Hacking. Facility is also provided for the recording of the "spread function". The angular field is somewhat in...
Topics: optical, analyser, slit, lens, spatial, modulation, image, bench, measurements, function, fourier...
R&D Report 1963-49 : Noise and vibration levels on the South Bank site of the proposed opera house and National Theatre. C.L.S. Gilford. Measurements of airborne noise and ground vibration on the South Bank of the Thames between County Hall and Hungerford Bridge show that the roofs of the proposed National Theatre and Opera House should give a mean sound reduction of 69 dB with a slope not exceeding 7 dB per octave. Protection of the National Theatre from vibration will present considerable...
Topics: vibration, opera, measurements, underground, ground, hungerford, maximum, theatre, national, site,...
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 1970-02 : Field-store standards conversion: The impairment caused by amplitude-perturbation of the colour subcarrier D.W. Osborne This report describes subjective tests which were made to determine the picture impairment introduced in the Mk 2A Field-Store Standards Converter when the quadrature-modulated intermediate chrominance subcarrier (which is of the NTSC type) is subjected to a systematic amplitude-perturbation, such as occurs in the converter. The tests showed that a...
Topics: amplitude, impairment, subcarrier, picture, tests, standards, waveform, colour, ntsc, signal,...
R&D Report 1973-10 : An automatic shot-change detector for telecine J.R. Sanders, M. Weston A system for the detection of shot changes occurring in films reproduced by telecine has been developed. This information is required for pre-programmed systems of telecine control and was, in the past, always obtained by visual inspection of the film in order to make a record, usually on paper tape, of the positions in the film at which shot changes occurred. The detector described in this report...
Topics: shot, integrator, detector, output, pulses, telecine, signal, film, bbc, video, successive fields,...
R&D Report 1982-05 : Carfax': the effects of co-channel interference. M.E. Bailey The Report describes subjective tests performed to ascertain the level of co-channel interference that would be tolerable during the reception of a "CARFAX" announcement, due to other distant "CARFAX" transmissions occurring simultaneously.
Topics: interfering, interference, signals, message, coded, carrier, tests, signal, transmitters,...
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 1975-01 : The estimation of the service areas of medium- and long-wave broadcasting stations. R.A. Rowden, C.P. Bell The aim of this report is to enable persons having no previous experience of the subject to make reasonably accurate estimates of the service areas of medium- and long-wave broadcasting stations, taking account of the vertical and horizontal directivity of the transmitting installation, its radiation efficiency, and the influence of the ground constants and of...
Topics: strength, field, conductivity, curves, aerial, interfering, transmitter, interference, field...
R&D Report 1981-09 : Improvements to speech quality from a diving helmet. D.J. Meares, K.F.L. Lansdowne The normal quality of speech received from a microphone in a diving helmet is far from acceptable for broadcasting, It is both severely distorted in terms of spectral content and, where air is supplied to the diver via a demand valve, the noise level from the demand valve is extremely high. This report examines, without losing the verisimilitude of the event.
Topics: noise, valve, equalisation, demand, diver, diving, speech, helmet, bbc, frequency, noise...
R&D Report 1987-15 : Theoretical and practical aspects of the "Functional Absorber" method of arranging sound absorbing panels. E.W. Taylor Measurements of the absorption of sound by functional absorbers (panels of porous material mounted so that both sides are exposed to the sound field) are described, the absorbers being arranged in a number of different configurations. The effect of increasing the surface density of the absorbing panels without significantly changing their...
Topics: absorption, absorbers, absorber, sound, panels, absorbing, reverberation, coefficient, arrangement,...
R&D Report 1961-07 : Crystal-diode modulators for the frequency range 10-1000 Mc/s. G.J. Phillips, R.G. Manton This report describes the development of low-power balanced diode modulators suitable for amplitude modulation by television or sound signals of a carrier in the frequency range 10-1000 Mc/s. From an original model, built in 1954, two later models have been developed having better performance in regard to the insertion loss at the carrier frequency, and uniformity of modulation...
Topics: modulator, modulation, frequency, insertion, signal, amplitude, impedance, transformer, output,...
R&D Report 1962-49 : Multiplex systems for stereophonic broadcasting G.J. Phillips, J.G. Spencer This report discusses the various systems which have been proposed for broadcasting stereophonic programme from a single v.h.f. transmitter. The results of laboratory tests on two systems are summarized. The first is the Zenith-G.E. system, adopted in 1961 by the F.C.C. for stereophonic broadcasting in the U.S.A. and more recently recommended by the European Broadcasting Union. The second is a...
Topics: stereophonic, subcarrier, monophonic, signal, reception, receiver, systems, system, modulation,...
R&D Report 1962-13 : Determination of the effective modulation depth of monophonic programme transmitted on the Zenith-GE stereophonic system D.E.L. Shorter In the Zenith-G.E. stereophonic broadcasting system, a small proportion of the available modulation capacity is taken up by a pilot signal used in the demodulation process at the receiver. The remainder is divided between the sum of the left- and right-hand stereophonic signals, transmitted in the same way as a monophonic programme, and...
Topics: signal, monophonic, stereophonic, programme, test, transmitter, level, modulation, amplitude,...
R&D Report 1962-46 : The Service area of the Les Platons VHF sound transmitters (1962). M.J. Buckley, J.H. Stewart This report gives the results of a field strength survey of the v.h.f. sound transmissions radiated from Les Platons in Jersey and Guernsey. Most of Jersey gets a satisfactory service, but about one fifth of the island of Guernsey is not served. An Engineering Information Department (E.I.D.) survey showed that the v.h.f. service in Sark from Les Platons is satisfactory but...
Topics: les, platons, strength, transmitters, ville, aerial, guernsey, field, les platons, receiving, field...
R&D Report 1963-46 : 'MINAR' - A miniature rack modular system for electronic equipment. T.N.J Archard, M.A. Hammond 'MINAR' is a modular system of unit construction based on a standard 19-inch x 5 1/4 inch (48.3 cm X 13.3 cm) panel, This panel is in the form of miniature rack into which units of various sizes may be inserted. The mechanical construction is straightforward and the overall assembly of units is capable of being used either in a standard 19-inch (48.3 cm) bay or in a portable...
Topics: det, panel, rack, mounting, unit, miniature, rods, units, carrying, standard, front panel,...
R&D Report 1970-22 : Television reception over sea paths: The effect of the tide P.A. Levan, D.W. Taplin, C.P. Bell On oversea paths within the horizon, the received field strength is the vector sum of a direct component and a component reflected from the surface of the sea. If the level of the sea varies, the relative phase of the reflected component alters and causes field strength variations. To determine the effect of these variations on UHF television reception, a series of...
Topics: fading, aerial, field, strength, receiving, reflection, path, vertical, tidal, variations, path...
R&D Report 1977-14 : Permissible timing jitter in broadcast PAL colour television signals. V.G. Devereux The report considers the results obtained from a number of different sets of subjective tests concerning tolerances for timing instabilities (referred to as jitter) in broadcast PAL colour-television signals. The magnitude of the timing errors considered is of the order of a few nanoseconds. These errors produce perturbations in the saturation and hue of colour areas of a displayed...
Topics: jitter, series, test, static, phase, sinusoidal, frequency, magnitude, tests, impairment, jitter...
R&D Report 1978-23 : The zone plate as a television test pattern. J.O. Drewery The zone plate pattern is a two-dimensional linear sweep of spatial frequency which can be used to give a quick appraisal of a television system's frequency characteristics. Applications discussed include measurement of filter characteristics, source and display properties, sub-Nyquist sampling system impairments, PAL coding and decoding and standards conversion. The pattern can be generated electronically in...
Topics: zone, frequency, plate, vertical, spatial, horizontal, sampling, components, hyperbolic, alias,...
R&D Report 1985-04 : Electronic detection and concealment of film dirt. R. Storey Film as an image source for television has four obvious impairments; film grain, dirt, unsteadiness and motion aliasing. The first three of these impairments can, at least in theory, be minimised electronically. For example, a previous Report has described the design of specialised electronic processing equipment to reduce the level of noise in a television signal; this is also very effective at reducing the...
Topics: dirt, motion, frame, detection, detector, spatial, film, signal, filter, aperture, difference...
R&D Report 1990-08 : A practical study of a vibration isolated room J.A. Fletcher It is common practice within the BBC to support studios and similar rooms on "anti-vibration" mountings (AVMs) in order to provide isolation from structure-borne sound. In practice these constructions do not usually achieve the designed resonant frequency. The isolation achieved is also rather doubtful. The source room of the transmission suite at Kingswood Warren, despite careful supervision of its...
Topics: resonant, vibration, frequency, room, source, floated, isolation, stiffness, amplitude, floor,...
R&D Report 1994-05 : Maximal-length sequence methods: Acoustic measurements in the presence of high levels of extraneous noise. R. Walker The use of the maximal-length sequence method to measure acoustic responses in the presence of high levels of extraneous noise is described. Direct and reliable measurements of time and frequency response functions down to a signal-noise ratio of 0 dB are possible. With modest amounts of signal-averaging, response functions down to S/N ratios of -20 dB...
Topics: measurement, frequency, measurements, impulse, signal, response, noise, sequence, averaging,...
R&D Report 1961-19 : Visit to Germany covering transmitting installations and the 1961 Berlin Radio Show. G.J. Phillips, D.E. Todd A four-day visit to Germany was undertaken to see transmitting installations in North Germany and Berlin, and to visit the two-yearly German Radio Show, held this year in Berlin. In Hamburg we also had discussions at the Institut fur Rundfunktechnik (I.R.T.). Special attention was paid to work in Germany connected with u.h.f. television transmissions, primarily...
Topics: transmitter, transmitters, band, mast, aerials, transmitting, aerial, television, siemens,...
R&D Report 1963-56 : 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 1964-62 : Acoustic characteristics of Maida Vale Studio 1. C.L.S. Gilford, D.K. Jones This report sketches the history of Maida Vale 1 studio from the time of acquisition by the Corporation. The major difficulty with this studio is the dip in the reverberation characteristic centred at 130 c/s which is shown to be due to vibration of the ceiling and which could be reduced by stiffening the structure. However, in view of the consideration being given to increasing the ceiling...
Topics: reverberation, ceiling, studio, frequency, stiffening, vibration, maida, absorption, woodwind,...
R&D Report 1965-21 : The Pumbicon camera tube J. Redmond, D.R. Morse, C.B.B. Wood The purpose of this report is to review the present technical performance of the plumbicon tube and to explore Philips' ability to supply the tubes which the Corporation may require for operation in future colour television cameras. The report discusses the current situation and arrives at the conclusion and recommendations which are set out in the main part of the report.
Topics: plumbicon, tubes, tube, camera, bbc, colour, sensitivity, philips, electronica, target, target...
R&D Report 1969-33 : The prediction of co-channel interference to television broadcasting services in the frequency range 470 to 960 MHz J.H. Causebrook, B. Davis, R.S. Sandell The operation over a period of four years of a computer programme designed to assist with the planning of a nework of television transmitters has revealed the need to carry out certain modifications. A description is given in this report of the revised method of calculating field strengths which has been incorporated...
Topics: terrain, correction, propagation, calculation, interference, field, method, angle, bbc, horizon,...
R&D Report 1969-51 : Car radio reception tests: Winter 1968/9 C.R.G. Reed, J.G. Spencer During the winter of 1968/9 observations on car radio reception in the UK were made by a number of BBC staff. Questionnaires were completed by 29 participants covering the reception quality of BBC services in the low-frequency (l.f), medium frequency (m.f) and very-high-frequency (v.h.f) bands. Analysis showed that the single l.f transmitter provided a reliable service over most of England and Wales. The...
Topics: receiver, reception, radio, interference, signal, frequency, grade, transmitter, car radio, tuning,...
R&D Report 1955-06 : The service area of the temporary television transmitter at Redmoss, Aberdeen. L.F. Tagholm, G.I. Ross, R.S.A. Sandell This report shows that the temporary transmitter at Radmoss, near Aberdeen, provides the city of Aberdeen with a reasonable television service using an effective radiated power of 3 watts. It is shown that the service will, in general, be similar to that expected from the final transmitter at Meldrum.
Topics: transmitter, aberdeen, temporary, redmoss, strength, vision, field, watts, field strength,...
R&D Report 1970-18 : Pulse code modulation for high quality sound distribution: Quantizing distortion at very low signal levels M.G. Croll In PCM systems, distortion of very low level signals is known to occur, and in high-quality programme distribution it is the most objectionable signal degradation caused by this kind of system. This report describes a series of subjective tests which show that it is necessary to use 14 bits per sample to code the audio signal in order to make this form...
Topics: distortion, granular, quantizing, noise, system, attenuator, input, signal, level, inaudible,...
R&D Report 1971-24 : Voltage breakdown in UHF feeders and combing equipment J.L. Eaton, N.H.C. Gilchrist The peak voltage in a transmitter feeder carrying four vision and four sound carriers exists for only about 2% of the total operating time, in the form of very short pulses (of about 10 nanoseconds in duration). It is reasonable to expect that the rating of feeders and associated equipment need not be specified to withstand the peak voltage under these conditions. The findings of this...
Topics: carriers, breakdown, voltage, field, peak, gas, feeder, electron, ionisation, free, sound carriers,...
R&D Report 1964-59 : Transmitting aerial for the Canterbury VHF television station. R.D.C. Thoday A brief summary of the installation of Canterbury Relay Station.
Topics: aerial, canterbury, yagi, transmitting, carrier, tower, oriented, aerials, templet, technological,...
R&D Report 1977-02 : Quadraphony: developments in Matrix H decoding. P.S. Gaskell, P.A. Ratliff The Matrix H 2-channel quadraphonic encoding system has been designed to transmit the maximum amount of directional information consistent with mono and stereo compatibility. This report discusses methods of decoding such transmission signals for 'surround-sound' reproduction. The basic form of decoder is a complex-coefficient linear matrix, but this has an inherent lack of separation between the...
Topics: matrix, logic, decoder, decoding, modified, separation, linear, signals, quadraphonic, basic, basic...
R&D Report 1963-08 : The suppression of corona- and precipitation-interference in vhf television reception: Thrumster experiments D.J. Whythe This report describes the results of a series of field tests conducted between November 1960 and August 1961 at the Thrumster station to assess the degree of suppression that can be provided against "precipitation-static" interference on television reception. For the tests, the interference levels from two aerial systems were compared both...
Topics: interference, aerial, subjective, thrumster, suppression, unprotected, protected, corona, receiver,...
R&D Report 1965-05 : Surface-wave feeders for U.H.F. site tests D.E. Susans This report describes experimental surface-wave feeders and launching horns for use with balloons for u.h.f. site tests. The general problems associated with design of this type of transmissions system are discussed together with the results on some practical feeders and horns.
Topics: horn, feeder, cable, dielectric, conductor, loss, feeders, balloon, power, conical, launching horn,...
R&D Report 1970-28 : A PCM sound-in-syncs system for outside broadcasts C.J. Dalton The standard Sound-in-Syncs system that has been developed for use on distribution networks has shortcomings when used on temporary links of poor quality. A ruggedised version is described which, in exchange for a reduction in audio bandwidth and signal-to-noise ratio, provides sound and vision circuits over links which have been degraded to an extent where they would normally be regarded as unusable. Field...
Topics: sound, pulse, signal, sync, input, syncs, pulses, video, ruggedised, separator, restored video,...
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 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 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 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 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 1964-78 : Transmitting aerials for the Hereford VHF television and VHF sound station D.W. Osborne A brief summary of the installation of Hereford Relay Station.
Topics: aerials, transmitting, horizontal, band, templet, gain, hereford, aerial, radiation, receiving,...
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...
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 1976-26 : Video digital filter Study II: Temporal first-order recursive digital filter. N.E. Tanton A study is being made of methods of reducing the level of noise in television picture signals. This Report describes a low-pass filter that acts in the temporal-frequency domain whilst allowing full spatial-frequency resolution of stationary scenes. The filter was built in a digital first-order recursive form. It works with 8-bit monochrome PCM signals at a 13.3 MHz sample rate....
Topics: filter, temporal, picture, filtering, noise, filtered, recursive, spatial, stationary, frequency,...
R&D Report 1957-03 : A new test signal for acoustic measurements - The coherent constant percentage bandwidth pulse. W.K.E. Geddes, C.L.S. Gilford. For the measurement of reverberation time, "warble-tone", bands selected from continuous spectrum noise, or pistol shots have hitherto been used as the test sound. As all three types of sound have disadvantages, apparatus which produces a repeatable continuous spectrum of known shape has been developed. This report describes the...
Topics: cathode, pulse, reverberation, pulses, bandwidth, frequencies, decay, tone, decays, discharge,...
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 1964-42 : Design of a free-field sound measurement room: The selection of sound absorbent material H.D. Harwood In designing wedge-type sound absorbers for use in a new free-field room, various kinds of plastic foam were considered as possible alternative to glass wool or glass fibre. The reflexion coefficient of the plastic materials was found to be influenced by mechanical resonances in the material, which in turn were markedly affected by the method of mounting the wedge. the...
Topics: reflexion, wedges, polyurethane, coefficient, ether, sound, wedge, absorbent, mechanical, rod, air...
R&D Report 1964-70 : UHF field trials 1962/63: laboratory tests carried out on prototype 625-line u.h.f. colour and monochrome receivers E.W. Taylor The characteristics of nine prototype 625-line colour receivers and fourteen 625-line monochrome receivers were evaluated in connection with the 'home-viewing' tests that formed part of the U.H.F. Field Trials which took place during 1962/63. This investigation was undertaken jointly by the BBC Designs and Research Departments. In this report,...
Topics: frequency, receiver, channel, carrier, signal, receivers, tuning, vision, ratio, measurements,...
R&D Report 1964-73 : Self-generated vision-on-sound interference in 625-line television receivers using intercarrier sound. J.G. Spencer, A. Jackson This report describes a mechanism by which non-linear distortion of the video-frequency signal in television receivers using the intercarrier sound technique can produce interference in the sound channel. The design features that affect the susceptibility to this form of interference are discussed and, as, an example, the results of objective...
Topics: intercarrier, sound, receiver, video, modulation, distortion, signal, interference, amplitude,...
R&D Report 1966-52 : Transmitting aerials for the Cambridge VHF television and VHF sound station D.W. Osborne, R.D.C. Thoday The Cambridge relay station came in to operation on the 7th March 1966. It provides a television and sound service to Cambridge, Fen Ditton, Cherry Hinton, Teversham and parts of Histon and Girton.
Topics: aerial, aerials, transmitting, band, mast, gain, receiving, horizontal, gasholder, templet,...
R&D Report 1969-47 : Viewing conditions for film review theatres T.W.J. Crompton This report describes viewing conditions for film review theatres used to appraise film for television purposes or for accurate colour grading. The advantages of conventional projection (e.g. simplicity, high resolution and shadow details) are preserved. The addition of a large illuminated surround of suitable brightness and colour temperature to the projection screen goes a long way towards subjectively...
Topics: surround, luminance, picture, viewing, ambient, film, colour, illuminated, brightness, screen,...
R&D Report 1971-35 : Protection ratios for 625-line System I television transmissions, impaired by interfering frequency-modulated television signals A. Brown Subjective tests have been carried out to find the protection ratio required by a 625-line system I television transmission, when the interfering signal is FM television. The effects of deviation, pre-emphasis, and energy-dispersal of the interfering signal are considered, as well as the addition of random white noise.
Topics: impairment, interfering, interference, protection, mhz, modulation, frequency, deviation, ratio,...
R&D Report 1995-01 : Modular acoustic diffuser: The development and performance of a modular acoustic diffuser. R. Walker, M.D.M. Baird The development of a prototype modular acoustic diffuser into a commercially reproducible product is described. The difficulties with materials, manufacturing processes and with fire-safety considerations are discussed. Acoustic measurements carried out on the final production modules showed that the diffuser met the acoustic requirements, despite...
Topics: diffuser, acoustic, absorption, modular, response, receiver, bbc, reflection, measurement,...