摘要:

A new arrangement is described in which a single resonance in a centimetre-wave cavity is used to give a discriminator action with high sensitivity and stability. The construction is considerably simpler than that of discriminators described previously, whilst the performance is free from all the errors that have been eliminated from the best of such discriminators. Only a single loop is used to couple with the cavity, and the discriminator action is obtained by arranging that this loop is self-inductive, so that the total impedance across it varies linearly with frequency near the cavity resonance. The output of this discriminator arrangement, however, contains a steady direct voltage, independent of frequency, but changing with the input power. This unwanted effect can be avoided by a switching arrangement used to vary the coupling between the loop and the cavity at some suitable frequency; 400 kc/s has been used. A tuned amplifier can then extract the output component at this frequency, and with a phase-sensitive-rectifier it is possible to obtain a discriminator characteristic output which is both amplified and free of serious errors due to changes of input power and drift effects in the crystal detector.An application of this discriminator to stabilize the frequency of a reflex-klystron oscillator is then described in which errors in the oscillation frequency are detected by the discriminator and are made to alter the reflector voltage on the klystron in such a direction as to reduce the error. The apparatus described has been in use for over a year and has made possible the generation of oscillations constant in frequency to one part in a million for periods of up to half an hour without readjustment.

DOI:10.1049/pi-3.1951.0016

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper discusses radio-wave propagation in the 70–300-kc/s band for long-distance navigational applications. Signals may reach the receiver by the ground path and by reflection from the E-layer of the ionosphere, the resultant signal at the receiver terminals being displaced in phase or time to a degree dependent upon the relative magnitude and phase of the component signals. Time-error curves are shown for typical propagational conditions, both by day and by night, at various frequencies. The errors which occur are classified as follows:(a) Systematic errors for which corrections corresponding to the propagational conditions present at the time can be applied.(b) Random errors which depend upon the difference between the ground- and ionospheric-wave paths.(c) Random errors arising from the imperfections of the ionosphere as a reflecting layer.The characteristics of these propagational errors are discussed, and the magnitude of navigational errors arising therefrom are deduced, using suitable examples. It is shown that, at intermediate distances, the random position-line errors are mainly dependent on the difference in the overground path distance, and that at large distances, they are dependent on the imperfections of the ionosphere as a reflecting layer.From phase and amplitude observations made with receivers in aircraft, during both day and night, the relative values of the ground-and ionosphere-reflected wave components were obtained as a function of distance from the transmitters; from these observations the virtual height of the reflecting layer and the reflection coefficient at oblique incidence were also deduced. The mean height of the reflecting layer is about 70 km in day-time and 90 km at night, with reflection coefficients at oblique incidence of 0.05 and 0.25 respectively.Using the Consol, Decca and Post Office Position Indicator transmitting systems, data collected from fixed receiving points at various distances from the transmitters show the variations of signal amplitude and phase which result from imperfections of the E-layer of the ionosphere when used as a reflecting layer. By collating these data, it is shown that navigational accuracy is improved by making the base-line distances as large as possible.

DOI:10.1049/pi-3.1951.0017

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper discusses some of the difficulties encountered when extending the load capacity of vibratory convertors, and, in particular, those which are imposed by contact deterioration due to arcing. Two methods are described by which these difficulties may be overcome, both making use of special circuits designed to reduce the current carried by the contacts at the moment they break the circuit. Reference is also made to methods of dealing with certain vibrator defects, and with transformer surges. Finally, examples are given of practical applications of the circuits described.

DOI:10.1049/pi-3.1951.0021

出版商:IEE    

年代:1951

数据来源: IET

摘要:

Impregnated-paper capacitors can fail in service from a variety of causes depending upon manufacturing and operating conditions. Under normal working conditions, the usual slow deterioration which ultimately leads to failure may be of an electrochemical nature. Factors influencing this type of deterioration are dealt with in some detail. Adverse factors are impurities, such as rosin and bitumen, which dissociate in the dielectric and accelerate the electrochemical processes, or the presence in the dielectric of moisture arising from poor impregnation or imperfect sealing. The effects of contamination are greater when polar impregnants are used, e.g. chlorinated hydrocarbons.Electrochemical deterioration of chlorinated dielectrics can be greatly reduced by the addition of “stabilizers.” A theory is advanced to explain the action of these stabilizers, and experimental evidence in support of the theory is presented.

DOI:10.1049/pi-3.1951.0023

出版商:IEE    

年代:1951

数据来源: IET

摘要:

A technique is described for determining the equivalent circuit ot a crystal resonator by measuring its frequencies of series and parallel resonance, its insertion loss as a series element in a suitable low-impedance transmission test-set and its capacitance at 1 kc/s. The effect of secondary responses on the equivalent circuit is discussed. A new test holder is used in which, with the aid of a microscope, specimens can be mounted in clamps at any desired point on their major surfaces. The results of measurements obtained on a number of types of quartz, ammonium-dihydrogen-phosphate and ethylene-diamine-tartrate resonators are given in tabular form. Illustrations of the effect of off-node mounting are included.

DOI:10.1049/pi-3.1951.0024

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The problem of the reflection and refraction of an electromagnetic plane wave at a plane interface formed by the edges of an infinite set of equidistant parallel metal plates has been studied, the plates being assumed to have no thickness and perfect conductivity. The direction of propagation of the incident wave is assumed to be at right angles to the edges of the metallic plates, and the electric vector is assumed to be parallel to them. The solution presented extends the scope of those already published, in that no restriction has been placed on the number of waves propagated away from the interface in the homogeneous medium; the reciprocal case of a wave incident from the plate medium has also been treated. Further, the mathematical method is simpler than that used in previous solutions.From the formulae derived, curves have been computed of the power-transmission and power-reflection coefficients, together with those of the phase changes across the interface. The formulae have also been tentatively applied to certain lenses, and the resulting curves indicate practical limits to the design of efficient lenses.

DOI:10.1049/pi-3.1951.0025

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The author has recently expressed the properties of a planar diode in terms of a set of differential coefficients, many of which can be experimentally determined. In the present paper these differential coefficients are used to derive a relation between the anode-current fluctuations and the fluctuation in the total emission.The fluctuation in the total emission is then calculated, and found in general to be much greater than the full shot noise. By inserting this result in the equation for the anode-current fluctuations it is found that the space-charge smoothing factor can be expressed in a very simple form. Its value can be determined experimentally from measurements of the characteristic at two slightly different cathode temperatures and the distance from cathode to anode. No measurement of temperature or total emission is necessary.It is well known that the fluctuations of valves and resistors can be expressed in identical forms, each involving a temperature. The results obtained in the paper show, however, that the fluctuations of a resistor are quite different from those of a valve, since they are not calculable from the shape of the characteristic without a knowledge of the temperature.

DOI:10.1049/pi-3.1951.0028

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-3.1951.0030

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-3.1951.0031

出版商:IEE    

年代:1951

数据来源: IET