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Contents Vol.34, No.3 March 2021 SILICON CHIP www.siliconchip.com.au Features & Reviews 10 Hoarding: Urban Electronic Archaeology Sorting through an extensive collection of electronic items is a task not too dissimilar to working on an archaeological dig site. It’s why it’s important to have items properly recorded to help sort the ‘rubbish’ from the ‘gems’ – by Dr David Maddison 30 Fetrons, and the All-Fetron Radio Fetrons are a solid-state replacement (typically drop-in) for pentode (sometimes triode) valves. I was so fascinated by them I decided to design a radio using only Fetrons – by Dr Hugo Holden 44 The History of Videotape – Quadruplex Our Battery Balancer can handle up to four series-connected batteries per unit, and suits most common battery types. It can handle batteries or cells from 2.5-15V, with a charging current up to 50A – Page 21 The first article in a series of four detailing the history of tape-based recording, starting with Ampex’s quadruplex recorder and ending with the move to digital video – by Ian Batty, Andrew Switzer & Rod Humphris 72 All About Capacitors There’s a lot to consider when choosing what capacitors to use for a design, due to the huge variety of them. This article explains how most capacitors are made, how each type differs and what performance you can expect – by Nicholas Vinen Constructional Projects 21 High-Current Four Battery/Cell Balancer – Part 1 Many battery balancers are inefficient due to dumping excess charge for a given cell. But our new Battery Balancer redirects that extra charge into other cells, charging faster with little heat or waste – by Duraid Madina 68 Mini Isolated Serial Link A look at the beginnings of videotape recording, starting with systems like the BBC’s Vera and Ampex’s quadruplex VR-1000A – Page 44 This postage-stamp sized module provides isolated, bi-directional, full-duplex serial communications. It can easily be used with our new Battery Balancer to charge even more batteries or cells – by Tim Blythman 84 Battery Multi Logger – Part 2 Following on from last month, we will go over the construction, setup, testing and calibration required to finish your Battery Multi Logger – by Tim Blythman 92 Electronic Wind Chimes – Part 2 In the final part of this series, we cover how to modify the wind chime itself so that it can be driven by a series of solenoids. You can then play your own tunes without relying on the wind – by John Clarke Your Favourite Columns This Mini Isolated Serial Link can be used with our Battery Balancer to manage even more batteries or cells. But it’s also useful any time you need to send isolated signals between two boards – Page 68 39 Circuit Notebook (1) Low-noise mic preamp (2) Two quartz crystal oscillators using a flip-flop (3) Displaying digits using single RGB LEDs (4) The Omnidetector 61 Serviceman’s Log If it isn’t one thing, it’s another – by Dave Thompson 100 Vintage Radio Kriesler Triplex 41-21 portable transistor radio – by Ian Batty Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback siliconchip.com.au 98 Silicon Chip Online Shop 106 Product Showcase 107 Ask Silicon Chip 111 Market Centre Australia’s magazine 112 Noteselectronics and Errata 112 Advertising Index Capacitors come in all shapes and sizes, and because of this it is confusing trying to pick one. So we’ve detailed some of the important aspects of capacitors, such as dielectrics etc – Page 72 March 2021  1 www.facebook.com/siliconchipmagazine