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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 Nicholas Vinen 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 David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Kevin Poulter Dave Thompson 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: Offset Alpine, Lidcombe, NSW. Distribution: Network Distribution Company. Subscription rates: $105.00 per year in Australia. For overseas rates, see our website or the subscriptions page 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. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 Recommended & maximum price only. 2  Silicon Chip Publisher’s Letter Digital technology is blanketing us with RF hash Few people would argue against the efficiency and compact size of switchmode power supplies compared with conventional supplies using iron-cored transformers. A typical switchmode supply will run at around 85% efficiency or better, while a conventional supply is typically 40% efficient or a lot worse. Switchmode supplies are also much more compact and weigh less. And nor would anyone argue against the advances brought about by digital data transmission, whether it is used in mobile phones, digital TV broadcasts or internet data via cable or phone connections. But without changes, all this wonderful technology means that AM radio broadcasts, in Australia and everywhere else around the world, will eventually become unusable. This fact was rammed home to me as I drove home one evening this week. As I came abreast of a bike rider, I noted that his flashing LED headlight was completely blanketing the AM radio on 702kHz. It sounded like speech - sheeschhhh – speech - scheeeschh . . . The light was really bright but I am sure the rider knew nothing about the rubbish he was radiating. In fact, all AM broadcasts below 1MHz are similarly blanketed if I drive near the local telephone exchange and several other pockets on my short journey home. Then, when I drive into my garage, there is another source of hash (which I have yet to locate) which plays havoc with reception. Inside my house, several CFL (compact fluorescent lights) radiate rubbish so if I want to listen to AM radio I have to orientate the receiver for best reception. In my nearby neighbour’s home, AM is unusable and the only way she can listen to her preferred stations is via a DAB+ radio. All of this occurs in an area where the AM signal is reasonably strong. In weaker signal areas, this hash means that AM is unusable unless you can resort to a loop antenna or an external antenna above the roof line. Sure, if you have a DAB+ receiver, you can listen to that but DAB+ is only available in the capital cities and there are plenty of areas where its signal strength is “below the digital cliff”. What can radio listeners do about these problems? While they might be able to control sources of interference in their homes, switching off certain appliances at the wall when they are not in use, their courses of action are quite limited. And nor can much be done about interference sources outside the home. Clearly, this situation requires action but the responsible body in Australia, ACMA, seems to be quite inactive in the face of the flood of imported products which are supposed to conform to radiated EMI standards but don’t. At one time, many years ago, when the Post Master General was in control of radio broadcasts and reception, they were quite vigilant about detecting and eliminating sources of radio interference. Why cannot ACMA at least move in that direction? It would not be a huge task for ACMA to have small teams of radio inspectors who could do surveys around cities and towns to locate sources of bad interference. The spectrum analysis equipment required is cheap, readily available and easy to use. With interference sources located, remedies can surely be proposed and implemented. In fact, ACMA could accelerate the detection process by letting the public log into their website to pinpoint bad locations. And as for switchmode equipment with bad interference, it does not have to be this way. ACMA only needs to inspect and reject a small number of products and publicise the facts, for improvements to come about. Without any action, AM broadcasts will die. Leo Simpson siliconchip.com.au