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SILICON SILIC CHIP www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc. (Hons.) Technical Editor John Clarke, B.E.(Elec.) Technical Staff Ross Tester Jim Rowe, B.A., B.Sc Mauro Grassi, B.Sc. (Hons), Ph.D Photography Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Mike Sheriff, B.Sc, VK2YFK Stan Swan SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Noble Park, Victoria. Distribution: Network Distribution Company. Subscription rates: $94.50 per year in Australia. For overseas rates, see the order form in this issue. Editorial office: Unit 1, 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. Fax (02) 9939 2648. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip Publisher’s Letter Oscilloscope probes are a vital link in looking at signals In all fields of electronics, the oscilloscope is regarded as the tool of choice. It gives you a means of looking at a vast range of signals, both analog and digital, audio, radio and higher frequencies. While you can always take voltages around a circuit, the oscilloscope will give a clear indication of whether the device is actually working, whether it has a fault condition or whether it is dead. Even if a circuit appears to be working perfectly, an oscilloscope can reveal if it has problems with a tendency to supersonic oscillation, for example, or whether it has overshoot, under-shoot, unduly long settling times or whatever. No wonder technicians and engineers regard the oscilloscope as being so indispensable. Without it, you are virtually blind and you are forced into proxy methods to determine whether a circuit is working or not. And yet, most people using oscilloscopes are quite cavalier in their use of probes. This is odd, because if you do not understand and use oscilloscope probes correctly, you can greatly degrade the quality of your observations. In short, you can turn an expensive wideband oscilloscope into a very ordinary instrument. Which is why we are pleased to feature this month’s article on oscilloscope probes by Doug Ford. It gives a very good description of how scope probes work, moving from the over-simplified explanation that is commonly quoted in textbooks and technical articles to a more detailed description of their operation as transmission lines. In fact, it demonstrates that there is far more technology involved in high-performance probes than you would think. So that’s why they can be so expensive to replace! Rational climate change debate has yet to take hold We are also very pleased to feature a long letter from Professor Ian Plimer in the Mailbag pages, on the subject of climate change. While many readers are probably sick of seeing references to the subject, we are extremely worried that moves to an emissions trading scheme (ETS), renewable energy targets (RET) and carbon pollution reduction scheme (CPRS) are extremely ill-conceived, will be expensive to implement and ultimately, will have zero effect on either carbon dioxide emissions from power stations, cars or any other human activity. Furthermore, they will have no effect on global warming, if in fact, it is still occurring or if it is anthropogenic (ie, caused by man’s activities) – itself unknowable at this stage of our knowledge on long-term climate. However, in virtually all of the debate on these measures, it seems to be accepted by most politicians and most of the media that global warming is definitely happening and furthermore, that it will be bad and must be stopped. Anyone that does not hold that view is likely to be pilloried as a “denier”, a ratbag or with epithets that are much worse. For example, Senator Steve Fielding has been ridiculed for asking why global warming has apparently stopped when carbon dioxide continues to rise. Yet Steve Fielding is no fool and is a qualified engineer. Professor Plimer’s book demonstrates that there are vast mechanisms at work which control our climate, virtually none of which are discussed in the popular panic over climate change. Nor is he the only one who promotes the view that man’s activities have negligible effect on our climate. There are thousands of scientists who agree with him. The sooner that politicians and the media take these contrary views more seriously, the better off we will all be. Leo Simpson siliconchip.com.au