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Contents Vol.38, No.02 February 2025 10 Open-Source Software There is a vast array of quality open-source software available, much of which is also free. We detail the different kinds of software available for various jobs such as video, image & audio editing, productivity, CAD etc. By Dr David Maddison, VK3DSM Computer software 24 Mini UPS Module This mini uninterruptible power supply (UPS) module provides continuous 9-12V DC <at> 10W. It’s suitable for smaller devices like a WiFi router, and it only requires a single lithium-ion cell connected to its 50 x 20mm PCB. By Jim Rowe Using electronic modules 40 Antenna Analysis, Part 1 Learn how antennas work and how to design matching circuits for them. In this first part, we cover the fundamentals, reactance, Smith charts and other related topics. By Roderick Wall, VK3YC Radio antennas 72 Precision Electronics, Part 4 In this fourth installment in the series, we look at how to extend the current measurement range of our current-sense circuit. We can do that by switching between two or more shunt resistors. By Andrew Levido Electronic design 32 High-Bandwidth Differential Probe This high-bandwidth and high-voltage Differential Probe is great to use with a ‘scope. With a max common-mode and differential-mode voltage of ±400V DC and rechargeable battery, it’s perfect for your test bench. By Andrew Levido Test equipment project 58 The PicoMite 2 The newest MMBasic interpreter for the Raspberry Pi Pico 2 and “W” variant is a comprehensive programming environment. It’s not only faster with more memory, it also has built-in support for HDMI video, USB keyboards, mice etc. By Geoff Graham & Peter Mather Raspberry Pi Pico project 64 IR Remote Control Keyfob This infrared (IR) remote control is one of the smallest we’ve made yet. It has three buttons that can be programmed wirelessly via NFC (near-field communications) and it works with many of our other projects. By Tim Blythman Remote control project 80 Programmable Frequency Divider This Divider/Counter reduces the frequency of an incoming signal by a factor of 3 to 21,327,000 and can be configured via USB. The input frequency can be 300Hz to 77MHz and is powered from 5-12V DC <at> 20mA. By Nicholas Vinen Test equipment project Project Page 32 High-Bandwidth Differential Probe Antenna Analysis and Optimisation Part 1: Page 40 PicoMite 2 Page 58 for the Raspberry Pi Pico 2 2 Editorial Viewpoint 5 Mailbag 31 Subscriptions 46 Circuit Notebook 48 Mini Projects 71 Silicon Chip Kits 88 Serviceman’s Log 94 Online Shop 95 Vintage Radio 100 Silicon Chip Kits 101 Ask Silicon Chip 103 Market Centre 104 Advertising Index 104 Notes & Errata 1. IR repeater 1. Power control for vehicle accessories 2. Power supply transformer tap switching 1. Wireless flashing LEDs 2. Transistor tester TRF-One AM radio by Dr Hugo Holden