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Contents Vol.34, No.4 April 2021 SILICON CHIP www.siliconchip.com.au Features & Reviews 14 Digital Radio Modes – Part 1 Digital radio is an extensive field utilised by amateurs, industry, military and government alike. This article discusses the various types of digital communication throughout the ages – by Dr David Maddison 64 The History of Videotape – Helical Scan Helical scan systems were in part designed due to the lack of a pause or still frame feature. They also offered lower tape speeds, leading to longer recording and playback times. Helical scan systems would also eventually overtake quadruplex in compactness – by Ian Batty, Andrew Switzer & Rod Humphris 100 Review: Wagner cordless soldering iron This new battery-powered soldering iron from Wagner Electronics can be recharged over USB and comes with three different tips. For example, one of the tips can be used for heat-shrinking – by Tim Blythman Constructional Projects Our Digital Effects Unit has 15 different effects, with the ability to customise eight. It’s powered from 9-12V DC, and includes true bypass and no signal inversion. It works well with piezo pickups due to its high input impedance – Page 24 24 Digital FX (Effects) Pedal – Part 1 This effects unit, based on the Spin FV-1 IC, is primarily designed for use with instruments, but can also be connected to a mic preamp or mixer. It has 15 different effects built-in (reverb, vibrato, distortion etc) and you can customise eight of them; the unit even has a true bypass feature – by John Clarke 36 Refined Full-Wave Motor Speed Controller Our brand new 230V 10A universal motor speed controller is vastly superior to previous models. Changes include an external feedback controller, the softstart feature can be turned off, and improved ability to maintain motor speed under load – by John Clarke 76 High-Current Four Battery/Cell Balancer – Part 2 In the final part of this series, we handle construction and testing of the Battery Balancer along with some safety tips – by Duraid Madina 88 Arduino-based MIDI Soundboard – Part 1 This new and improved Motor Speed Controller works with universal and shaded-pole motors up to 10A. It has external feedback gain adjustment, optional soft-start and current feedback – Page 36 This simple project turns an Arduino into a 64-key MIDI matrix, which can be used similarly to a 61-key beginners’ keyboard. The MIDI shield includes a basic synthesiser and audio amplifier, making it easy to test – by Tim Blythman Your Favourite Columns 46 Serviceman’s Log I hope the purists won’t spit their dummies – by Dave Thompson 61 Circuit Notebook (1) Biofeedback for stress management (2) Latching output for Remote Monitoring Station (3) Alternative switched attenuator for Shirt Pocket Oscillator (4) Follow-up to ‘constant’ AC source 102 Vintage Radio 1948 Philips table model 114K – by Associate Professor Graham Parslow Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback 87 Silicon Chip Online Shop siliconchip.com.au 99 Product Showcase 107 Ask Silicon Chip 111 Market Centre 112 Noteselectronics and Errata Australia’s magazine 112 Advertising Index The 64-key MIDI matrix is a simple Arduino project which can be used to trigger sounds. It also incorporates its own synthesiser and audio amplifier – Page 88 April 2021  1 www.facebook.com/siliconchipmagazine