R&D Report 1963-15 : Television co-channel interference: The effect of the polarity of modulation. W. Wharton If the frequency difference between the vision carrier frequencies of two co-channel television stations is correctly chosen, the visibility of the interference pattern is reduced to a minimum. In this case, the frequency difference (usually termed the offset) must be maintained with considerable precision; the method of operation is termed "precision offset". In this...
Topics: interference, modulation, brightness, amplitude, carrier, polarity, frequency, visibility, wanted,...
R&D Report 1962-10: V.H.F. sound broadcasting: Mutual interference between transmissions with 100 kc/s channel separation radiating either the same or different programmes. J.G. Spencer Subjective tests have been carried out, using four recent models of domestic a.m./f.m. sound receivers, to determine to permissible ratio of wanted- to unwanted-carrier levels when an interfering f.m. transmission is spaced by 100 kc/s from a wanted f.m. transmission and is broadcasting either the same or a...
Topics: interference, signal, ratio, programme, frequency, transmission, receiver, interfering, modulation,...
Communications, Radar & Electronic Warfare
Topics: radar, figure, radio, antenna, signal, frequency, warfare, electronic, interference, jamming,...
R&D Report 1968-43 : Calculation of the field strength required for a television service, in the presence of co-channel interfering signals. Part 2: Effect of multiple interfering sources E. Sofaer With the great expansion in television services in Europe and elsewhere, several transmitting stations will be operating in the same frequency channel. To any one service all transmitters sharing the channel are sources of interference, and it is therefore necessary that some method of estimating...
Topics: probability, deviation, location, signal, standard, field, interference, protection, strength,...
R&D Report 1971-10 : Reduction of adjacent-channel interference in the LF and MF broadcast bands by reduction of the modulation bandwidth C.R.G. Reed Abstract Transmitter carrier frequencies in the LF and MF broadcast bands assigned under the Copenhagen Plan of 1946 are, for the most part, separated by 9 kHz. Transmitters and receivers operating in these bands are usually designed for a modulation bandwidth greater than 4.5 kHz although the receiver response may be appreciably attenuated at...
Topics: khz, interference, modulation, signal, filter, frequency, bandwidth, receiver, tests, interfering,...
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 1974-20 : Satellite broadcasting: channel separation requirements for FM television signals N.H.C. Gilchrist A practical investigation has been conducted in order to determine the frequency separation required between FM television signals, both with and without a sound subcarrier, so that mutual interference is avoided. The investigation was concerned primarily with interference between PAL colour television signals, but brief tests were conducted to determine the requirements...
Topics: mhz, signal, filter, receiver, frequency, channel, signals, sound, interfering, tests, sound...
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,...
BBC Monographs Collection
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A.J. Pilgrim, K. Hacking, D.E. Susans, C.R.G. Reed, S.W. Amos
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BBC Engineering 89, January, 1972. A.J. Pilgrim, K. Hacking, D.E. Susans, C.R.G. Reed, S.W. Amos. * Editorial: Prospects for the Improvement of Reception in the M.F. and L.F. Bands * Principal Articles:The Move into Broadcasting Centre, Birmingham * Synchronous Demodulation in L.F./M/F/ Receivers * Reduction of Interference by Reduction of Modulation Bandwidth * An Active Deflector for U.H.F. Television Broadcasting.
Topics: receiver, modulation, signal, frequency, filter, bbc, khz, interference, bandwidth, carrier, wanted...
R&D Report 1964-32 : Local oscillator interference with UHF television reception J.G. Spencer This report discusses the possible effects of local-oscillator interference, from u.h.f. and v.h.f. receivers, with u.h.f. television reception. Measures which can be taken in respect of u.h.f. station planning and receiver design in order to minimize these effects are indicated.
Topics: interference, receiver, receivers, monochrome, iii, radiation, aerial, frequency, aerials, colour,...
R&D Report 1959-24 : A F.M. receiver incorporating a new type of limiter and discriminator. J.G. Spencer This report describes a f.m. receiver, covering the band 87.5 to 100 Mc/s, which incorporates a recently developed limiter and discriminator circuit. While comparable in cost and complexity with the simpler type of domestic receiver which relies on a ratio detector for amplitude limiting, it provides a higher degree of amplitude-modulation suppression than such receivers generally attain.
Topics: limiter, discriminator, signal, input, ratio, receiver, frequency, amplitude, tuning, suppression,...
R&D Report 1966-15 : Compatible single-sideband modulation: Experimental investigation of the performance with conventional AM receivers. J.B. Izatt A laboratory investigation is described of the overall performance of a compatible single sideband (c.s.s.b) system when used with current types of domestic receivers. The systems employs an alternative method of amplitude modulation to that normally used in the l.f., m.f. and h.f. broadcasting bands, the sideband on one side of the carrier...
Topics: signal, interference, modulation, receiver, fading, audio, receivers, tuning, measurements,...
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,...
Electronics: Communications, Radar & Electronic Warfare (2011)
Topics: radar, figure, radio, signal, antenna, frequency, interference, warfare, electronic, jamming,...
R&D Report 1971-32 : A feasability study of an adaptive system for UHF television D.E. Susans, J.G. Spencer This report describes the results of an investigation into the feasibility of producing an adaptive receiving system for UHF television suitable for rebroadcast links in situations where, with standard techniques, there would be unacceptable interference. The system is designed to adjust continuously the directivity pattern of a receiving aerial array so as to steer minima onto the...
Topics: interference, signal, adaptive, system, test, synchronising, waveform, aerial, pulse, aerials,...
R&D Report 1962-14 : Co-channel interference between television signals of the same or different standards. G.F. Newell, E.W. Taylor This report describes measurements of the ratios of the amplitudes of wanted and interfering signals which produce a particular subjective grade of interference. The measurements were made in order to ascertain the required protection ratios for mutual interference between two stations each operating on any of the three television standards at present in use...
Topics: interference, offset, signal, protection, frequency, ratios, offsets, interfering, required,...
R&D Report 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 1984-12 : The susceptibility of aeronautical navigational aids to interference from adjacent-band broadcast transmissions. G.H. Millard Measurements to determine the susceptibility of some airborne navigation receivers to interference from v.h.f/f.m sound transmissions are described. The measurements were designed to investigate both the response to interference radiated in-band and to intermodulation in the receivers . The results of the measurements were submitted to an ITU...
Topics: receiver, ils, interference, intermodulation, frequency, signal, mhz, broadcast, transmissions,...
R&D Report 1987-09 : A digital audio link to the Channel Islands in the UHF television band: preliminary experimental results M.C.D. Maddocks A digital link at UHF has been proposed as a means of feeding radio programmes over the long sea path to the Channel Islands. An experimental link has been installed to test the viability of such a proposal. Results from the first five months of operation are presented in this Report.
Topics: link, signal, measured, uhf, performance, predicted, field, digital, data, strength, wanted signal,...
R&D Report 1989-07 : Use of an HF active monitoring array in the presence of high level interference. K.L. Beeke An electronically-steerable, active receiving array for HF was developed at BBC Research Department a few years ago. An investigation has now been carried out to find the limiting operating conditions for the array, i.e. under what maximum levels of interference it can be operated satisfactorily. Typically, it has been found that if interference levels are greater than about 100...
Topics: signal, interference, level, levels, amplifier, screening, bbc, array, whip, active, interference...
R&D Report 1962-19 : Television co-channel interference at very low offsets. E.W. Taylor The subjective appearance of the patterns that are produced when a television transmission suffers co-channel interference at very low offsets is described, and the protection ratio required at these offsets is discussed. In the case of non-offset working, an assessment is made of the improvement of the frequency stability of each of the two vision carriers required to give a worth-while reduction of...
Topics: offset, protection, ratio, frequency, required, nominal, interference, offsets, television, scan,...
R&D Report 1963-14 : Television co-channel interference: Some effects of the modulation of the interfering signal. E.W. Taylor The configuration of the interference pattern produced when a television transmission suffers co-channel interference from another television signal is examined in detail, in order to determine the process by which the interfering modulation gives rise to additional patterns. The description of these patterns in terms of the carriers and side-bands of the two...
Topics: interfering, frequency, pattern, signal, wanted, sideband, subsidiary, sidebands, principal,...
R&D Report 1974-21 : Satellite broadcasting: channel separation requirements for FM television signals and for a FM sound signal adjacent to a FM television channel N.H.C. Gilchrist This report describes experimental work carried out to determine the frequency separation required between high-deviation FM sound signals, and between FM sound and FM television signals, when they are transmitted on adjacent channels. A frequency separation of 0.8 MHz is recommended for situations where two FM...
Topics: signal, sound, mhz, frequency, ratio, interfering, separation, television, adjacent, signals,...
R&D Report 1984-09 : Satellite broadcasting: the performance of C-MAC in a hardware simulation of a DBS transmission chain. P. Shelswell This report describes a series of experiments and gives details of measurements of C-MAC, a new transmission standard for direct broadcasting by satellite, when passed through a hardware simulation of a complete satellite transmission chain. The quality of the vision and sound (or digital data) were monitored throughout the chain, for the nominal chain and...
Topics: transponder, output, channel, interference, spectrum, mhz, psk, loop, amplitude, signal, data...
BBC Monograph 25: A Quality-checking Receiver for V.H.F. F.M. Sound Broadcasting. C.G. Mayo, R.E. Jones.
Topics: receiver, frequency, ratio, modulation, oscillator, bbc, output, suppression, interference,...
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 1963-41 : Line-store standards conversion: Subjective effect of unconverted components V.G. Devereux This report describes experiments that were carried out in order to investigate the subjective effects of interference caused by 'break-through' of unconverted input signal to the output of a 625-line/405-line line-store standards converter. The effects of two different forms of 'break-through' were investigated; the first form was that which would result from an aperiodic...
Topics: signal, interference, luminance, interfering, visibility, slide, display, attenuation,...
R&D Report 1969-09 : The susceptibility of portable band II FM receivers to interference by services operating in adjacent frequency bands C.R.G. Reed Nine portable receivers, designed for FM reception and retailing at prices ranging from under 10 to over 25 pounds, were tested for their susceptibility to interference by an amplitude-modulated signal whose carrier frequency differs from that of the wanted signal by between 300 kHz and 3.5 MHz. The tests were repeated on some of the...
Topics: signal, interfering, receiver, receivers, frequency, tests, modulation, interference, deviation,...
R&D Report 1972-04 : Interference characteristics of dual-standard monochrome television receivers operating in the UHF bands C.R.G. Reed This report gives the results of a series of measurements made in 1970 on the interference-rejection characteristics of six British monochrome dual-standard (Systems A and I) receivers operated in the UHF bands (Bands IV and V) using System I.
Topics: receiver, interference, signal, channel, mhz, amplitude, receivers, frequency, signals, carrier,...
R&D Report 1973-05 : Ionospheric non-linearity: Protection ratios required against cross-modulation interference (Luxembourg Effect) D.J. Whythe, C.R.G. Reed Studies of intermodulation of a weak signal by a strong signal in the ionosphere have defined the degree to which the level of intermodulation varies as a function of modulation frequency of the strong signal. This report describes experiments which show that, as a result, a 6 dB relaxation, relative to co-channel interference, may be...
Topics: modulation, ionospheric, interference, bbc, ionosphere, frequency, signal, interfering, capacitor,...
R&D Report 1956-41 : C.W. interference with television: Its reduction by means of frequency modulation. A.V. Lord, R.V. Vigurs This report has been written as the result of work carried out on a proposal by E.P. Wethey to reduce the visible effect of c.w. interference on a television picture. The proposal relies on the principle that if an interference pattern is broken up by the use of frequency modulation at the transmitter, the protection requirements can be somewhat relaxed. The report...
Topics: frequency, carrier, interference, modulation, receiver, deviation, vision, monochrome, colour,...
R&D Report 1976-13 : A VHF multipath simulator. D.E. Susans A description is given of a VHF multipath simulator intended for use in laboratory comparisons between different VHF sound transmission systems such as standard FM, wide-deviation FM and PSK systems. Provision is made for generating single or multiple echoes with delays of up to 100 microseconds and, for some modulation systems, adjacent- or co-channel interference can also be simulated. This equipment is a valuable tool for...
Topics: delay, output, multipath, frequency, fading, delayed, oscillator, signals, variable, simulator,...
R&D Report 1978-33 : M.F. andL.F. reception: susceptibility of domestic receivers to interference. R.V. Harvey Self-generated interference in domestic lf and mf broadcast receivers has been investigated theoretically and the susceptibility of five typical receivers has been measured. A systematic analysis of the results has been attempted and a procedure established for assisting planning exercises by assessing the likelihood of interference from particular combinations of frequencies.
Topics: khz, frequency, interference, frequencies, receivers, interfering, mechanism, signal, coefficients,...
R&D Report 1985-02 : An electronically-steerable active receiving array for h.f. A.P. Robinson The array described offers advantages over the directional aerials commonly used for monitoring at h.f.. It is compact and can be steered electronically in any direction. A steerable null may be placed in the radiation pattern. Active elements are used so that the effects of mutual coupling are negligible. The array comprises eight short, vertical monopoles in a line, the outputs of which are...
Topics: null, array, delay, pattern, direction, mhz, broadside, beam, signal, main, radiation pattern,...
