History of wireless telegraphy and broadcasting in Australia/Topical/Publications/Australasian Radio World/Issues/1951 03

Front Cover

Australian Radio & Electronics

incorporating

Australasian Radio World

Registered at G.P.O., Sydney, for transmission by post as a periodical.

MARCH, 1951 - Vol. 15, No. 8

1/6

P.01 - Contents Banner

AUSTRALIAN RADIO AND ELECTRONICS

and incorporating

AUSTRALASIAN RADIO WORLD

Vol. 15 - MARCH, 1951 - No. 8

P.01 - Contents

CONTENTS

Our Cover . . . . 1

Editorial . . . . 2

R. & E. Gramophone Pre-Amplifier . . . . 4

N.B.F.M. Adaptor . . . . 9

A Regulated Power Supply (by the Eng. Dept. Aerovox Corp.) . . . . 15

Novice Set-Building — A Section for the Beginner . . . . 16

R. & E. Television Project for Home Construction (Part 3) . . . . 18

A Direct Reading Audio Frequency Meter (Part 2) . . . . 22

"Ham" Activities . . . . 25

Short Wave Review . . . . 29

Classified Advertisements . . . . 32

Our Front Cover

The quality of the electrical steel used for Rola output transformers is checked with the aid of this Magnetic Comparator. The sample of standard steel and the test piece are placed in the central hole of the two balanced inductors shown at the top of the equipment which is then adjusted so that the pattern shown on the oscilloscope may be correctly interpreted.

P.01 - Publication Notes

Subscription Rates: 12 Issues 18/- Post Free

Published by the Proprietors: Radio & Electronics (N.Z.) Ltd. (Publishers - Incorporated in N.Z.) 17 Bond Street, Sydney, N.S.W.

Correspondence: All correspondence, contributions, and enquiries referring to advertising space and rates should be addressed to our Registered Australian Office:

The Editor, "Radio and Electronics", 17 Bond Street, Sydney, N.S.W., Telephones: BU3879, BW7746, Telegrams and Cables: "Cranlay", Sydney

Managing Editor: LAY. W. CRANCH, AMIRE (Aust.), M.W.I.A., VK2XC

Providing National Coverage for the Advancement of Radio and Electronic Knowledge

Sole Wholesale Distributors - Gordon & Gotch (A/asia) Ltd.

Wholly set up and printed in Australia by R. V. Byers, 9 Wetherill St., North Lidcombe. 'Phone: UX6681 (Footnote P.1)

P.02 - Editorial

Editorial

Electronics is a powerful, but comparatively new, tool, which is finding ever-increasing applications in industry, and it is to be hoped that it will continue to do so. There is, however, one particularly important feature of electronic equipment that may retard, rather than increase its usefulness, unless the designers of electronic devices give it more than passing thought. We refer to the question of reliability. Competent engineers realize that in a sense, electronics has grown up too quickly, and in some degree has even over-reached itself a little. The very fact that many things are more easily done electronically than by other means, together with the ability of electronics to do many more things that can not be done at all otherwise, has tended to make some workers think that electronics is a panacea or a kind of philosophers' stone. For just as many jobs can be done only by electronics, so too, many more hold no possible application for it. But it is not in either of these categories that the danger lies. It is in a third class of problems, which can be solved either by electronics, or by purely electrical or mechanical means, that electronic designers and engineers must exercise caution. These problems must be examined very carefully, as to cost, reliability, and ease of maintenance, before a decision is made for or against the electronic method. In many cases, first cost can actually be lower when the electronic solution is chosen, but cost may be quite unimportant compared with reliability. There are very few engineering projects where reliability is not of paramount importance, and it is here that responsible engineers have to think twice about the use of valve-operated equipment. It is an unfortunate thing, but a true one, that many of the fundamental processes upon which electron tubes rely for their manufacture or operation are still not properly understood. For instance, the exact mechanism by which electrons are made available by a cathode is still a matter for argument among physicists. Now this may not at first sight appear to have much to do with the reliability of vacuum tubes, but it has. For the most part our valves rely for their supply of electrons on composite cathode materials which are difficult to make, are very easily "poisoned" by minute amounts of impurities, and which even depend for their success on minute traces of other "impurities" whose role is not properly understood. Present-day valves are thus rendered more difficult to apply, because the cathode materials in use are sensitive, among other things, to the exact temperature at which they are run. In equipment which must be as reliable as possible, therefore, it becomes necessary to use controlling devices which regulate the voltage fed to the valve heaters, in order to maintain them at the right temperature. There is always the temptation to do without voltage control, cheapening the product and possibly reducing its reliability below the level that is really required. Who knows but that a fuller fundamental understanding of electron emission may not lead to the development of cathodes whose heating is so uncritical as to make voltage control unnecessary, even for the best equipment? This is merely one example of how increased knowledge could make electronic gear more dependable. But we have to work with the valves that exist, not with the improved ones the makers, of such things hope to develop. What, then, can we do to see that dependability is improved? An analysis of failure in the field has shown that there are three major causes of unserviceability in valve-operated equipment. They are (1) the use of valves when some other device would, have been more suitable; (2) the failure to select the best valve for the particular application; and (3) actual errors in design of the equipment, and the inadequate provision of protective devices which could prevent a breakdown of the complete equipment. It can be seen, therefore, that the design engineer can do a great deal to improve reliability. In the first place, he must ask himself whether a valve is needed, and if so, why? If the answer to this question is in the affirmative, he must investigate the possibilities should the valve fail. In many cases, failure can cause no more than inconvenience, as when the radio set goes out of action in the middle of an exciting serial, but in others, a valve failure may mean loss of property or even life. Where failures of this sort could occur, it is the designer's responsibility to make any failures "safe." In some equipment this means completed duplication with provision for automatically bringing in the standby gear when a failure occurs, while in others, a simple alarm indicator will suffice. It has been said that the greatest single threat to reliability is the continual pressure on the makers of tubes, by the users, to increase tubes' ratings. The opposite question — that of increasing the life expectancy of valves by working them under their ratings — is hardly ever raised, but by so doing, designers could undoubtedly save a multitude of tube failures which occur at less than the normal life expectancy of the valve concerned. These, and many other factors all contribute to the unreliability of things electronic, but no discussion of the problem would be complete that does not mention the question of maintenance. Here, education is necessary, not only for the designer, in the way he should go, but for the user, who should know how frequently routine inspections should be carried out, especially in the case of equipment on whose operation life and property depend. Lastly, there is education for those; whose direct responsibility the maintenance will be. The equipment itself, or its designer, cannot be blamed for failure which is due to improper maintenance but it is none the less in the interests of the producer of electronic goods to see that the users of his products have a proper appreciation of the maintenance that is required.