摘要:

The paper describes some of the procedures for finding out whether a given component is suitably designed for incorporation in a range of radio or television receivers, and gives a survey of some of the results obtained in carrying out such tests in one particular laboratory. Many of the tests applied to components are of a straightforward routine kind, such as the measurement of capacitance, resistance or inductance of normal values by standard methods; these are not described in detail, but where a measurement is made by an unusual method or where special test machinery of general usefulness has been devised a fuller description is given.The tests come under three main headings: mechanical, electrical and chemical. Under each of these headings there are three kinds of tests: measurement, such as of mechanical or electrical dimensions; life tests, in which the component is tested in some way representative of the effects of normal use, over a period of about five years and peak-load or overload tests.

DOI:10.1049/ji-3-2.1948.0014

出版商:IEE    

年代:1948

数据来源: IET

摘要:

An analysis is made of the response of an a.m. receiver to impulsive interference (of the type generated by car ignition systems) using the Fourier integral theorem. Conclusions concerning the general behaviour of receivers are deduced from the formulae developed. The method is then applied to the calculation of the performance of noise suppressor circuits which are classified as amplitude, differential and delay limiters. Simple expressions are derived for estimating the suppression attainable in any particular case.Some experiments are described in which the performance of the first two types of noise suppressor was measured. There is shown to be fair agreement with the calculated values.A comparison is made between the behaviour of frequency modulated, pulse-length-modulated and suppressed amplitude-modulated systems with impulsive interference.

DOI:10.1049/ji-3-2.1948.0017

出版商:IEE    

年代:1948

数据来源: IET

摘要:

A large class of radio circuits which are analytically equivalent to an oscillatory network in parallel with a non-linear negative resistance, are represented fairly accurately by the differential equationv̈− (α+βv−γv2)v+ ω2v=Eω21sinω1twhere, α/ω, β/ω, γ/ω are small. The behaviour of the solutions of this equation near resonance has been discussed by Appleton, van der Pol and others.The paper contains a more complete discussion of the synchronized and quasi-periodic solutions near resonance, their phases, amplitudes and energy, and also the way in which one type of stable solution gives way to another as the parameters of the system vary, for instance as the electromotive force or detuning vary. It is shown that the phase and amplitude favourable to synchronization are prolonged just before synchronization. This agrees with Appleton's experimental results. It is also found that hysteresis occurs. The decrease in energy with the decrease in detuning is explained by the fact that the phase favourable to synchronization is that which opposes the motion and is prolonged.

DOI:10.1049/ji-3-2.1948.0020

出版商:IEE    

年代:1948

数据来源: IET

摘要:

The paper deals with effects of localized obstacles, including reflection as well as shadowing, which are of practical importance in radio communication and radar, particularly on decimetre and centimetre wavelengths. In a digest of available theoretical results, later compared with the experimental findings, attention is drawn to some unresolved difficulties. In most of the practical problems discussed, prediction to a useful approximation is, however, shown to be possible.The experimental work described has been carried out by or for the Admiralty, and much of it had its origin in the special problems of naval communications and radar. It has, however, wider applications at almost every point; applications to radar navigation are specifically discussed.

DOI:10.1049/ji-3-2.1948.0021

出版商:IEE    

年代:1948

数据来源: IET

摘要:

An analysis is given of the response of a linear diode-voltmeter to r.f. impulses, of the indication of a meter measuring the rectified voltage, and of the damping effect of the diode on the preceding circuit.The response to a short single impulse of arbitrary shape is evaluated in terms of the time-integral or area of its envelope. The ratio of this area to the peak amplitude is termed the effective duration of the impulse.The response to recurrent impulses whose spacing is small compared with the discharge time-constant is expressed in a general manner and graphed for the cases of rectangular and triangular impulses. The “effective charge time-constant” of the voltmeter depends on impulse and circuit parameters. The rectification efficiency for triangular impulses is found to lie between 0.75 and 1 times that for rectangular impulses of the same effective duration and periodicity. It is inferred that for most practical impulses the rectification efficiency will lie between the values shown graphically for triangular and rectangular impulses when expressed in terms of effective duration of the impulse.The maximum indication of a critically damped meter to the rectified voltage produced by the application of a single impulse is evaluated in terms of the ratio of the meter and discharge time-constants.The damping imposed by the diode rectifier on a sharply tuned circuit is calculated for single and recurrent impulses and shown to be considerably greater than for continuous waves.

DOI:10.1049/ji-3-2.1948.0022

出版商:IEE    

年代:1948

数据来源: IET