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SILICON CHIP Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons .) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advertising Manager Paul Buchtmann (02) 982 9553 Regular Contributors Bryan Maher, M.E . B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill Jennifer Bonnitcha, B.A. Bob Young Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd, Rozelle , NSW 2039. Printing: Macquarie Publications Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates: currently $42 per year (12 issues) inside Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139 , Collaroy Beach , NSW 2097 . Phone (02) 982 3935 . Fax (02) 982 9553. ISSN 1030-2662 2 SILICON CHIP PUBUSHER'S LETTER Power lines and the environment: a touchy subject During the month of March, the ABC program "Countrywide" had a segment about a rural community in New South Wales protesting about high voltage power lines crossing their land. Now this subject has been discussed to some extent in the June 1989 issue of SILICON CHIP and my attitude in the past has been to dismiss most claims about the effects of power lines on human beings. But the power lines in the Countrywide program were of a totally different magnitude and I couldn't help feeling some sympathy for the protesters. Forget the whacky claims made about power lines in the past which have generally been concerned with voltages of up to lOOkV AC or more. It is difficult to conceive that these have any biological effects or if they do, they must be very small. But what if the voltage on the power lines is 600,000 volts AC and the current is thousands of amps? What if the voltage gradient is high enough to light up fluorescent lamp tubes carried by people walking under those power lines? What if you are a farmer cultivating crops every day with those power lines passing overhead? Wouldn't you feel just a trifle edgy? I know I would. Apart from the dangers, real, imagined or unquantified, who really wants those monstrous gantries marching across the landscape, especially if you own the land? And I can think of a third reason why the farmers would not want those extremely high voltage power lines close by. Think of the effect they could have on TV and radio reception. Corona discharge at 600,000 volts AC is a dandy of a problem. That's why you see very high voltage cables hanging in pairs or groups of three or four - it simulates a much larger cable diameter and thereby cuts down corona discharge. No, the more I think about it, the more I am sympathetic to the farmers. We all need electrical energy but maybe the real cost of transmitting it at such extreme voltages is just too high. Maybe the time has come when such high voltages are no longer politically acceptable. Maybe we should accept the slightly higher losses of transmitting electrical energy at lower voltages and then put the power lines underground. It is not cheap or easy but it has been done before. In the future there is no doubt that all large engineering projects will be subjected to much greater scrutiny with regard to their effect on the environment, on people's health and well-being, and on safety. High voltage transmission lines certainly come into this category and if they are subject to much closer questioning, then that is probably a good thing. Leo Simpson