Aerial Space Research Articles

Studies on the Feeding Habits of the Brown Planthopper, Nilaparvata lugens (STÅL) (Hemiptera : Delphacidae) : IV. Probing Stimulant

The brown planthopper was observed to make only infrequent attempts to probe the aerial space or distilled water behind a parafilm membrane. Most of the stylet sheaths produced in these regions were very short and did not brnch. Sucrose and aspartic acid showed little influence on the probing response despite their action as sucking stimulants.Salicylic acid was found to stimulate the stylet probing, and its optimum effect was recorded when 0.001 to 0.004 M salicylic acid was present together with 2% sucrose. In such media, the planthopper deposited a large number of branched and well extended stylet sheaths similar to those produced in rice plant tissues, indicating an enhanced stylet probing response. Other aromatic monocarboxylic acids accurring in rice plants had no effect.Salicylic acid suppressed the sucking response at the efficient concentratios at the probing stimulant. The saps obtained from rice plants and four kinds of non-host plants stimulated stylet probing of the brown planthopper.

An investigation of the ground diffraction pattern of radio waves reflected by the ionosphere

An experimental investigation of the spatial correlation of amplitude fading records of echoes from the E-region has been carried out, with a view to testing the validity of the assumption that the spatial and temporal autocorrelograms have identical shapes. Results of the analysis of a large amount of data show clearly that although the shapes are similar, all values of spatial correlation are in general under-estimated. An important consequence of this is that the semi-diameter ( d) of the characteristic ellipse is also under-estimated. The effect is very marked for small aerial spacings, but the calculated value tends towards the true value as the aerial separation increases. The under-estimate of d will produce errors in the velocity and direction of drift calculated by full correlation analysis, which will be most severe when small observing triangles are used.

Investigations of North‐South Ionospheric Movements at a Low‐Latitude Station

Cross‐correlation and ‘similar fades’ time delays obtained on widely spaced aerial pairs in the north‐south direction have been used in investigating north‐south ionospheric motion at the low‐latitude station of Ibadan (magnetic latitude, 3°S), and a north‐south velocity of considerable magnitude is revealed. It is also found that, if an aerial spacing of at least one‐half kilometer is used at this latitude, systematic diurnal and seasonal variations of this velocity can be detected. The procedure of the analysis is briefly outlined, and the reliability of the results is discussed.

Design Considerations of Spacers for Aerial Spacer Cable

The design considerations for the use of high alumina in spacers for spacer cable are discussed. The spacer configuration is a function of the characteristics of the insulation materials involved?both the spacer and the phase conductor covering. Electrical considerations dictate a minimum of material in the spacer consistent with mechanical requirements. A new equivalent circuit, coupled with a method for comparing the voltage division between a spacer and the phase conductor covering, permitted evaluation of new designs. Flashover tests for the latest spacer design are reported. Surface leakage test results show the relative merits of ceramic and fluorocarbon coatings in reducing leakage due to salt contamination. The tests in which bare phase wires were used are most revealing. A simple design for a contamination testing facility is included.

Instrumental and Data Processing: Correction of High-resolution Solar Scans

Correlation radiotelescopes have become increasingly important in the last few years in all types of astronomical observations. These instruments operate by multiplying (correlating) the outputs of two separate aerials in order to provide a composite antenna with a range of aerial spacings and orientations. As a general rule this range of spacings is truncated at both the largest and smallest spacings, the largest spacing being determined by the area available or by the cost of the system, and the lowest spacing by either cross coupling between the multiplying elements (as in the Mills Cross type) or by the geometrical size of the elements (as in the compound interferometer type).

Design Considerations of Spacers for Aerial Spacer Cable, N. A. Smith, IEEE Trans. Electrical Insulation, vol. EI-4, pp. 12-17, March 1969

Design Considerations of Spacers for Aerial Spacer Cable, N. A. Smith, IEEE Trans. Electrical Insulation, vol. EI-4, pp. 12-17, March 1969

New Power Cable Insulations Based on Covulcanized Blends of Ethylene Propylene Rubber and Polyethylene

New power cable insulations based on covulcanized blends of ethylene propylene rubber (EPR) and polyethylene (PE) have been developed. These heat-, water-, ozone-, and highly corona-resistant insulations combine many of the desirable properties of both ethylene propylene rubber and polyethylene. Specific constructions of low-voltage, heat and moisture resistant power cables, aerial spacer cables, and portable power cables are reviewed and compared with existing constructions. It is felt that, compared to rubber insulated cables, the use of these new insulations can result in smaller diameter cables which exhibit many improved properties over thermoplastic or cross-linked polyethylene cables.

Impulse Characteristics of Aerial Spacer Cable

Although the overall performance record of aerial spacer cable on the Public Service Electric and Gas Company system has been excellent, the number of failures caused by lightning appears to be disproportionately high. To determine the optimum design criteria of this type of distribution system, a program of laboratory impulse tests was established. This paper presents the results of the laboratory tests, with volt-time curves for various components of the spacer cable system. This study is one of several performed by the Public Service Electric and Gas Company.

Studies of ionospheric forward scattering using measurements of energy distribution in azimuth

Measurements of phase and amplitude have been carried out on signals on 37Mc/s received from a transmitter at Gibraltar. The receiving sites were at Slough and Castlemartin, which are each about 1740km from Gibraltar, and were equipped with pairs of aerials whose spacing could be varied from λ to 10λ. The results were not consistent with the idea that the forward-scattered signal was due to the combination of many randomly-phased radio waves. Frequently one signal appeared to be dominant, as might be expected if reflections from meteor trails formed an important part of the resultant signal. The calculation of an azimuth power distribution on the basis of phase measurements with different aerial spacings then becomes of uncertain validity. Some results obtained in this way are presented, but reliance is placed mainly on work with a small, fixed aerial spacing. This shows a marked diurnal variation of mean bearing; at Slough for most of the year it is on average 7°W of the Gibraltar bearing by night but 0°W by day. A comparison with observations at Castlemartin in Wales suggests that the scattering process is due almost entirely to meteor reflections by night but that during the day there is also present a component due to turbulent scattering which contributes rather more than half the total energy.

A Phase Sensitive Interferometer Technique for the Measurement of the Fourier Transforms of Spatial Brightness Distributions of Small Angular Extent

A method is described whereby the amplitude and phase of the complex Fourier transform of a spatial brightness distribution of small angular extent may be uniquely determined from a series of measurements with a triple interferometer system. Absolute measurement of the amplitude function is available, whilst measurements of phase are relative to a datum obtained at short aerial spacings. A practical radio frequency interferometer incorporating the principle is described and its operation is discussed.

The practical evolution of the commutated-aerial direction-finding system

The paper sets out to show how the more fundamental problems encountered in the development of the commutated-aerial direction-finding system have been solved during a long-term development plan. Reasons are given for the choice of a circular array of aerials, which are commutated sequentially to the receiving equipment. It is shown how such an arrangement permits great economy in the number of aerials required for a given system performance, maximum adjacent aerial spacing being much larger than might at first appear permissible, and the method for computation of the signal bearing is described in some detail. Significant features of the development are described, particularly where problems are peculiar to the system, such as realization of adequate selectivity despite aerial commutation and the avoidance of the effect of aerial interaction. Final practical circuits are described for signal processing and demodulation, and for the display of bearing, and it is shown that the solutions adopted should permit realization of the performance predicted by theoretical study some 10 years ago. Although practical experience in the field is not yet large, adequate practical measurements have been made to substantiate most of the theoretical predictions with regard to performance.

27. Intensity distribution across the Cygnus and Cassiopeia sources

Measurements of the angular distribution of intensity across the intense discrete sources in Cassiopeia and Cygnus have previously been handicapped by lack of knowledge of the phase of the Fourier transform at very long aerial spacings. The technical difficulties of measuring the phase of the transform and also of calibrating the absolute amplitude have been solved by a new technique involving three stations. This method enables the phase to be measured relative to a frame of reference within the source and obviates the need for retaining the phase angles accurately constant on the removal of one of the aerial systems to a new site. The phase measurement is not limited to observations of the central fringe, and useful measurements may be made on all the fringes contained within the aerial polar diagrams.

Diffraction microscopy and the ionosphere

The application of diffraction microscopy to Mitra records is considered. It is shown that its application to existing records might result in some slight improvement, probably scarcely justifying the effort. If, however, tests should show that the combination would work with aerial spacings of 3–10 λ, the advantages of the combined method would be substantial. An important practical limitation on any type of Mitra method is the complexity of the record normally obtained, and it may prove impossible adequately to analyse any but the simplest of them by any technique. The question of future development is briefly touched on.

Radio Emission from the Andromeda Nebula

OBSERVATIONS have been made at a wave-length of 3.7 m. with interferometers of different resolving powers to determine the distribution of radio brightness across the Andromeda nebula, M31, which has also been investigated at radio wave-lengths by Hanbury Brown and Hazard1. When observations are made with small movable aerials, errors are caused by reception of radiation from adjacent radio stars. Good discrimination was therefore obtained with the present measurements by using several different sections of the large Cambridge radio telescope2, although this method reduced the number of different axes and aerial spacings available. The relationship of the four axes used to the Andromeda nebula is shown in Fig. 1.

Rain clutter measurements with c.w. radar systems operating in the 8-mm wavelength band

The objects of this work were to investigate the extent of rain clutter using 8-mm continuous-wave radar systems with both a single aerial (common transmission and reception) and dual aerials (separate transmission and reception) and to investigate the reduction of this clutter by orthogonal polarization techniques. In the common transmission and reception case using polarization duplexing, the amplitude of the rain clutter was measured in terms of decibels below the valve power level by a direct comparison method and plotted against the rainfall rate in millimetres per hour. This was also done for the separate transmission and reception case, which did not employ a duplexer. The results showed that the rain clutter amplitude in the common transmission and reception case was some 60 db below valve power level for a moderate rainfall of 3 mm/h. In the separate transmission and reception case rain clutter decreased with increasing aerial spacing and was some 95 db below valve power for a rainfall rate of 3 mm/h with 2-ft diameter aerials spaced 3 ft centre to centre. Details of the methods of measurements, the equipment used and the experimental observations are given.

Some practical measurements of the relative performances of a cyclical phase-comparison type of direction-finder and a U-Adcock instrument

Simultaneous bearing observations were made using a cathode-ray direction-finder of the U-Adcock type and a multi-aerial wide-aperture instrument (PV2) employing cyclical differential measurement of phase. The transmitters observed operated in the frequency band 8–12 Mc/s and were located at distances ranging from 750–1500 km. In the analysis of the data, where particular attention was paid to the rapidly varying component of the bearing changes, it was found that for the majority of the transmitters studied the spread of bearings was significantly greater with the Adcock than with the other direction-finder. The reasons for this difference are discussed and it is inferred that a large part of the superior performance of the PV2 was due to its relatively large aerial spacing. Although the Adcock instrument gave the better performance in the presence of interfering signals, a higher proportion of observations were lost with it owing to deep fades.

The Radio Brightness Distributions over Four Discrete Sources of Cosmic Noise

Brightness distributions have been obtained across the four radio sources, Cygnus?A, Taurus?A, Virgo?A, and Centaurus-A, using a two-aerial interferometer of a special type in which the aerial spacing and the azimuth angle of the axis may be varied over a wide range. Radio isophotes have been constructed for three of the sources from these results, making some simple assumptions as to their form. The isophotes bear some relation to optical features of the nebulae with which the sources have been identified and their radio and optical sizes are similar. The remaining source, Cygnus?A, is unfavourably situated for observations from Sydney, and the results are less complete.

An investigation of polarization errors in an H-Adcock direction-finder

The polarization-error characteristics of H-type Adcock direction- finders operating in the v.h.f. band and in the upper part of the h.f. band are controlled to a large extent by resonance phenomena. A theoretical and experimental investigation of a rotating system for very high frequencies has demonstrated the feasibility of calculating, from the physical dimensions of the aerial system, the frequencies at which large errors are liable to occur, and also the magnitudes of the maximum errors. The lowest resonant frequency is that for which the product of aerial length and spacing is one-twentieth of a square wavelength. A second resonance occurs when the spacing is half the wavelength and, if the aerial length is approximately equal to the spacing, the third resonance occurs when the spacing is 0.8 times the wavelength.Three major causes of polarization errors are discussed and formulae are given for calculating these errors. The agreement between the calculated and measured errors at the resonant frequencies suggests that the three causes discussed account for nearly all the errors. Various methods of minimizing errors are examined theoretically and experimentally.Although the instrument used for the experimental investigation was designed for very high frequencies, the results have application to a wider band of frequencies and to instruments of both fixed and rotating types.

The Position and Movement on the Solar Disk of Sources of Radiation at a Frequency of 97 Mc/s. I. Equipment

The spaced aerial interference technique, au used in radio astronomy, has been modified in order to observe solar disturbances winch are either of short duration or are rapidly changing in position. The interference pattern is obtained in 1/25 of a second by sweeping the aerial lobe pattern across the source, 25 times per second. The position of the source and the polarization of the radiation are determined separately, a complete record taking about one second. Two different aerial spacings are used and calibration is carried out by a novel method. An equipment operating on 97 Mc/s., which has been used for observations of solar disturbances, is described and the sources of error discussed.

An analysis of the performance of multi-aerial Adcock direction-finding systems

This paper presents a theoretical discussion of the performance of crossed fixed-aerial Adcock direction-finder systems employing more than two aerial pairs. Comparison is made with the conventional four-aerial Adcock system, with regard to both spacing error and sensitivity.Improvements are obtained by increasing the total number of aerials over the four of the conventional Adcock system, so that, for a given accuracy, a gain may be achieved either in frequency coverage or sensitivity, or in both together. It is also shown that an increase in the number of aerials above eight is of little practical advantage, since the spacing for small errors approaches the absolute limit of 1.22λ.A modified system, in which two aerials are connected in parallel to replace each of the single vertical aerials, is also discussed. This system has a performance nearly as good as the fully symmetrical eight-aerial system, and when used in conjunction with a twin-channel receiver it is expected to give the better performance.Finally it is shown that a star connection of the aerials provides a correct sense signal, only when the aerial spacing is less than 0.76λ.