A.J. Gibson

Rutherford Appleton Laboratory

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Co-Authors

L. Thomas

Max Planck Institute of Geoanthropology

M. C. W. Sandford

Central Coast Local Health District

P.A. Bradley

University of the West of England

S. K. Bhattacharyya

Bharatiya Vidya Bhavan

M.T. Chryssomallis

Democritus University of Thrace

L. Arnett

Rutherford Appleton Laboratory

M.R. Bowman

Rutherford Appleton Laboratory

AÖ

A. Özgüç

Kandilli Observatory and Earthquake Research Institute

Cemil B. Erol

TUBITAK BILGEM

Jonathan King

National Institute on Aging

Cooperative Institutions

Rutherford Appleton Laboratory

University of Birmingham

Kandilli Observatory and Earthquake Research Institute

Boğaziçi University

Reckitt Benckiser (United Kingdom)

Istanbul Technical University

Space Research Institute

National Physical Laboratory

Democritus University of Thrace

University of the West of England

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A method for stabilising an air-spaced Fabry-Perot etalon

Journal of Physics E Scientific Instruments (1977)

S. K. Bhattacharyya A.J. Gibson

A simple method is described for stabilising the optical thickness of the air gap in a piezoelectric Fabry-Perot etalon. The spacing between the plates is controlled by an error signal proportional to the difference in intensity of two orthogonally polarised modes of a frequency stabilised He-Ne laser.

Air gap (plumbing)

SIGNAL (programming language)

10.1088/0022-3735/10/9/010

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Citations (3)

Ionospheric propagation correlation statistics for service planning

A.J. Gibson

The present paper extends the spatial correlation results in Gibson et al. (1993) to a longer period of data and other receiver separations. New analyses are presented of correlations of signals at separated frequencies and with geomagnetic activity. Data were collected at frequencies from 7.9 to 19.1 MHz on a 2600 km path from Cricklade in England to the Kandilli Observatory near Istanbul during the period from April 1992 to February 1993, with a different second receiving site during each of the first three months. Small (quiet-time) variations of signal strength from day to day may involve fluctuations in f0F2, hmF2, and f0Es, whose causes cannot usually be identified and hence are called 'geophysical noise'. Larger variations, as reviewed for example by Davies (1990) and references therein, tend to be associated with events on the sun, including sudden ionospheric disturbances, ionospheric storms, polar cap absorption events, large scale travelling ionospheric disturbances, and associated disturbances in the geomagnetic field.

QUIET

Polar cap

10.1049/cp:19950384

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Citations (0)

Azimuthal distribution of noise and interface at HF

Antennas and Propagation, 1993., Eighth International Conference on (1993)

A.J. Gibson L. Arnett

The predictions of atmospheric and man-made noise in CCIR Reports 322 and 258 are for short lossless, grounded, single vertical monopole antennas, but practical antennas may differ from the CCIR reference antenna in many respects. The antenna directivity may be expected to affect both noise and spectral occupancy statistics. Experimental information on the effects of directivity on noise is scarce, and in some respects conflicting. Most previous spectrum occupancy studies have used omnidirectional antennas, but some results with directional antennas have recently been reported. The paper reports further measurements at a site in Southern England.

Directivity

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Citations (1)

Ruby laser damage associated with a liquid Raman frequency changer

Journal of Physics D Applied Physics (1968)

A.J. Gibson

Rapid damage to a Q-switched ruby laser, caused by the use of a Raman frequency changer, has been observed. The effect is interpreted as due to stimulated Brillouin scattering in the Raman liquid.

Ruby laser

Brillouin zone

10.1088/0022-3727/1/7/415

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Citations (4)

Some characteristics of cirrus clouds deduced from laser-radar observations at different elevation angles

Journal of Atmospheric and Terrestrial Physics (1977)

A.J. Gibson L. Thomas S. K. Bhattacharyya

Cirrus

Backscatter (email)

Elevation (ballistics)

Extinction (optical mineralogy)

Molar absorptivity

10.1016/0021-9169(77)90079-4

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Citations (11)

A steerable laser radar system for atmospheric studies

Optical and Quantum Electronics (1978)

Kankan Bhattacharyya A.J. Gibson Ernest C. Hammond M. C. W. Sandford L. Thomas

Position (finance)

10.1007/bf01208856

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Citations (4)

Day-to-day variation of HF signal strength and noise

Electronics Letters (1990)

A.J. Gibson

Measurements of the day to day variations of signal and noise on 120 and 970km paths at 9.3 and 15.7MHz are compared with CCIR reports. Appreciable correlation is found between signal and noise, indicating a need for modification to existing fading allowances for HF service planning.

Signal strength

SIGNAL (programming language)

Day to day

Variation (astronomy)

10.1049/el:19900498

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Citations (1)

A flashlamp-pumped dye laser for resonance scattering studies of the upper atmosphere

Journal of Physics E Scientific Instruments (1969)

A.J. Gibson

A flashlamp-pumped dye laser has been developed to measure minor constituents of the upper atmosphere by resonance scattering. The construction of the laser and the procedures for tuning are described in detail. The spectrum has been narrowed to 5 pm, tuned to one of the sodium D lines, and measurements of atmospheric sodium have been made. The possibility of measuring other atmospheric constituents by the same method is briefly considered.

10.1088/0022-3735/2/9/312

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Citations (27)

Measurements of fading on HF communication links

Antennas and Propagation, 1989. ICAP 89., Sixth International Conference on (Conf. Publ. No.301) (1989)

A.J. Gibson

Although much is known about the amplitude statistics of fading on ionospheric paths, CCIR preparations in high-frequency broadcasting for the World Administrative Radio Conference (WARC-HFBC) revealed a lack of knowledge, for both within-an-hour and day-to-day variations of: (i) the correlations of signals and noise; (ii) the correlations of fading on adjacent channels; and (iii) the correlations of fading at different receiving sites within the coverage area of a broadcast transmitter. Consequently, fading allowances adopted in planning standards for reliability and compatibility need to be validated or replaced. A programme of measurements, which will consist of a series of campaigns, each of about one month's duration, involving different receiving sites throughout Europe covering ranges of 400-2500 km, is currently being undertaken by RAL, with assistance from DTI, to meet this need. The paper presents preliminary analyses of data collected during the first campaign which took place during September-November 1988.

Source

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Citations (1)

Laser radar measurements of the atmospheric sodium layer

Journal of Atmospheric and Terrestrial Physics (1970)

M. C. W. Sandford A.J. Gibson

Twilight

10.1016/0021-9169(70)90102-9

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Citations (85)