摘要:

The variations in the frequencies of quartz oscillators compared with that of a caesium standard are described and discussed. It is shown that the frequencies of the ring-type oscillators at the N.P.L and other laboratories do not depart from those given by a linear law of variation by more than ±5 parts in 109over a period of three years. The quartz oscillators calibrated by the caesium standard have been used to study the variations in the period of rotation of the earth. In addition to an annual seasonal variation of approximately ±8 parts in 109, there was a fairly steady retardation amounting to 1 part in 108in the period between September, 1955, and January, 1958.

DOI:10.1049/pi-b-2.1960.0104

出版商:IEE    

年代:1960

数据来源: IET

DOI:10.1049/pi-b-2.1960.0107

出版商:IEE    

年代:1960

数据来源: IET

DOI:10.1049/pi-b-2.1960.0108

出版商:IEE    

年代:1960

数据来源: IET

摘要:

In radio trunk systems a number of two-way radio channels are used over a common route with repeaters provided at intervals. Each radio channel carries a baseband signal by frequency modulation of the radio carrier frequency. The baseband signal may consist of an assembly of single-sideband telephony channels and/or a television channel.When choosing the frequency pattern for the radio channels, selectivity requirements are found to arise, not only from the primary fact that the channels are adjacent in the frequency spectrum, but also from secondary features of the equipment such as, for instance, the intermediate frequency used in the heterodyne repeaters.The paper considers the effects which give rise to such selectivity requirements and shows how to choose the channel frequency pattern and the intermediate frequency to minimize the selectivity requirements. The choice takes account of amplitude non-linearity in waveguide circuits. The presence of this was expected on theoretical grounds and has been confirmed by measurements.A specific frequency pattern is worked out for a route with six two-way channels in which each radio channel can carry at least 600 telephone channels or a single television channel. This arrangement was adopted by the C.C.I.R. in 1956.

DOI:10.1049/pi-b-2.1960.0109

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper describes a method of generating approximately a quadrature signal from a given signal using a linear network comprising a tapped delay line. It is shown that a vestigial-sideband signal free from phase distortion can be produced by this means.An experimental version of the quadrature network described has been constructed, and the paper includes the results obtained using the network to produce a vestigial-sideband version of a 405-line television signal with a video bandwidth of 3 Mc/s.It is suggested that a high-power vestigial-sideband signal could be produced by this means with some saving in transmitter power.

DOI:10.1049/pi-b-2.1960.0112

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Solutions are obtained for the modulation-product currents in series- and shunt-type rectifier modulators by separating out an equation for each possible modulation-product frequency and by assuming (a) square-wave switching of non-reactive rectifiers, and (b) signal-path terminating impedances which are a pure but not necessarily constant resistance—or zero or infinite—at each modulation-product frequency involved. The conditions under which there are no even-order modulation-product currents are determined, and the influence of such currents when they do exist is examined. Experimental results confirm the theory. It is shown that all the working and conclusions apply exactly to the ring modulator, provided that terminations required for odd-order modulation-product frequencies are applied in the output loop and those required for even-order frequencies are applied in the input.

DOI:10.1049/pi-b-2.1960.0113

出版商:IEE    

年代:1960

数据来源: IET

摘要:

It is shown how the input impedance of a rectifier modulator of series, shunt or ring type can be calculated, and a large number of cases are tabulated, assuming (a) that the terminating impedances, while being as frequency selective as desired, are nevertheless purely resistive at all modulation-product frequencies where they are not zero or infinite, and(b) that the rectifiers have a square-wave variation of resistance with time. It is clearly shown that in all cases except one (i.e. a ring modulator with constant-resistance load) the input impedance—defined as the ratio of the input voltage to the input current at the applied signal frequency—has the peculiar property of being dependent on the nature and magnitude of the signal-source impedance from which it is being measured.

DOI:10.1049/pi-b-2.1960.0114

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The properties of a gas discharge which make it suitable for voltage stabilization are discussed. Various types of corona discharge are described, and it is shown that a corona discharge between a wire anode mounted axially in a cylindrical cathode is the most suitable for voltage stabilization. To obtain the required low impedance it is necessary to use hydrogen as the filling gas. The effect of dimensions on the voltage and impedance of the discharge is discussed, and characteristics of various tubes which have been developed as corona voltage stabilizers covering a range of 350–7000 volts are shown. Finally some of the applications of such tubes and their appropriate operating conditions are given.

DOI:10.1049/pi-b-2.1960.0117

出版商:IEE    

年代:1960

数据来源: IET

摘要:

A method is described for calculating the dispersion characteristics and coupling impedance of a Karp-type slow-wave structure. The structure is regarded as a ridge waveguide, periodically loaded with short-circuited stub lines. The analysis is simple and lends itself to the speedy assessment of the performance of a particular circuit.Measurements on 8 and 4 mm experimental backward-wave oscillators are described and are shown to verify the usefulness of the approximate theory. These results are also compared with those obtained by field-theory analyses.

DOI:10.1049/pi-b-2.1960.0118

出版商:IEE    

年代:1960

数据来源: IET

摘要:

Apparatus is described for the rapid determination of the cut-off frequencies,f1and fα, of transistors in the 20–1000 Mc/s range. Accurate measurements at these frequencies are made possible by the application of transmission-line techniques to the method of comparing the high-frequency voltages which appear across small resistors connected to two leads of the transistor. Methods are adopted which separate the measuring circuits from the input circuit and make the design of the latter non-critical. The relative accuracy off1andfαmeasurements is discussed, and it is concluded that the inherently more accuratef1measurement should have an error within ±5%, whereas the error in fαis probably 2–3 times higher. A few typical measurements are given.

DOI:10.1049/pi-b-2.1960.0119

出版商:IEE    

年代:1960

数据来源: IET