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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP FOR SALE KIT ASSEMBLY & REPAIR LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au tronixlabs.com.au – Australia’s best value for supported hobbyist electronics from Adafruit, SparkFun, Arduino, Freetronics, Raspberry Pi – along with kits, components and much more – with same-day shipping. PCB PRODUCTION PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com DAVE THOMPSON (the Serviceman from SILICON CHIP) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz MISCELLANEOUS ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects like audio, video, programming etc. The books are relatively old in most cases and vary in condition. You'll need to come in person to see what books we have and what we're willing to sell: Silicon Chip 1/234 Harbord Road (up the ramp) Brookvale NSW 2100 (02) 9939 3295 VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. 3.3V power line or faulty Mosfet (Q1). Ferrite bead impedance/ resistance requirement I have a query regarding your 6GHz+ Frequency Counter Parts list (siliconchip.com.au/Series/319). On page 33 of the October 2017 issue, the parts list calls for a “low resistance SMD ferrite bead”. As I was ordering most of my parts from DigiKey Electronics, I also ordered a ferrite bead, Cat 240-2411-1-ND. siliconchip.com.au However, I now realise that this ferrite bead has a resistance of 160W and looking at the circuit, I can see that it is part of a pi filter feeding a couple of regulators. Not knowing the exact current draw, I am guessing that the voltage drop is going to be excessive across this ferrite bead. Could you let me know what ferrite bead was used for this project, eg, the part number and supplier? (J. T., Redwood Park, SA) • According to the specifications Australia’s electronics magazine on the Digi-Key website, 160W is the impedance of the ferrite bead at the test frequency, which in this case is 100MHz (a typical test frequency). The requirement for “low resistance” in this project is that it must have a low DC resistance, because a significant current (up to about 1A) is flowing through it and we don’t want too much voltage loss. The ferrite bead you’ve selected has a DC resistance of 18mW, ie, 0.018W which is certainly low enough. So it’s certainly suitable. SC January 2019  111