~ Early Web Links ~

A comprehensive reference hub dedicated to the Smith Chart, the classic RF engineering tool invented by Phillip Smith of RCA, covering tutorials, software downloads, example charts, reference books, and curated links to related tools and pages. Visitors can explore the mathematical foundations of impedance matching, s-parameters, and microwave design through a well-organized collection of articles, Java applets, and PDF resources.

Aaron Cake's extensive collection of electronic circuit schematics covers categories from power supplies and light/laser projects to telephone circuits and sound/radio designs. Each circuit includes printable PCB patterns, community rankings, and user comments, making it a hands-on resource for hobbyist electronics builders.

Electronics Notes, created and maintained by engineer Ian Poole, is a comprehensive reference hub covering electronics theory, circuit design, components, radio technology, antennas, ham radio, and more. With tutorials aimed at everyone from hobbyists to professionals, it also offers downloadable guides, infographics, and component data sheets, making it a genuinely useful destination for anyone working with electronics.

The Music Electronics µArchive is a long-running reference hub for DIY guitar effects and audio electronics, offering schematics archives, FAQs, and curated links to the best resources on the web. Highlights include a downloadable schematics archive, guides on tube amplifiers and transistor identification, and an Electro-Harmonix parts sheet for builders working with vintage pedal components.

Tonne Software offers a catalog of free and low-cost electrical engineering programs for Windows, covering filter design, meter scale drawing, great-circle mapping, Smith charts, and more. The site also hosts technical articles and tutorials on topics like speech processing, AM demodulators, and CW bandpass filters, many published or submitted to QEX magazine.

Phi's personal digital garden covers a range of technical and creative interests including electronics, music, DIY, mathematics, physics, and railways. A cozy old-web style homepage with an 88x31 button for linking, inviting visitors to explore whatever useful or interesting content Phi has cultivated here.

KA7OEI is Clint's technically-focused amateur radio and electronics blog, covering hands-on modifications and experiments with devices like the MFJ-5008 parabolic ultrasonic receiver. This particular post dives deep into improving the sensitivity and frequency response of the discontinued ultrasonic tool, with detailed photos, circuit analysis, and practical applications like bat detection and power line fault finding.

DiscoverCircuits.com, run by engineer Dave Johnson P.E., is a massive repository of over 45,000 free electronic circuits and schematics cross-referenced across 500+ categories for engineers, hobbyists, inventors, and students. Online since 2002, it serves as a go-to reference for quick design ideas, circuit solutions, and component resources covering an enormous breadth of electronic applications.

Alan Yates (VK2ZAY) runs a sprawling electronics and amateur radio laboratory notebook covering homebrew circuits, microcontrollers, high voltage experiments, pyrotechnics, antennas, and much more. With over 260 articles, engineering calculators, and an annual Advent Calendar of Circuits series, this is a genuine treasure trove for hands-on electronics hobbyists.

FC's Electronic Circuits is a sprawling hobbyist archive packed with schematics and project descriptions covering everything from solar charge controllers and LED circuits to tube amplifiers, Geiger counters, and amateur radio gear. With dozens of original circuit designs, Arduino projects, and links to related ham radio and electronics builders, this site is a goldmine for DIY electronics enthusiasts.