~ Early Web Links ~

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.

A specialized reference guide cataloging the vacuum tube types used in shortwave radio broadcast transmitters, organized alphabetically and numerically for easy lookup. The site also lists manufacturers, rebuilders, and distributors worldwide, including companies like Thales, Eimac, Penta Laboratories, and Xuguang, making it a practical industry directory for broadcast engineers.

Electronics 2000, created by Simon Carter, is a comprehensive hobby electronics reference packed with online calculators for resistors, capacitors, inductors, Ohm's Law, and more, plus technical data articles, pin-outs, and a beginner's guide. The site also offers downloadable Windows software like Electronics Assistant and an EPE Index, making it a genuinely useful toolkit for hobbyists, students, and engineers alike.

Peter's RF schematics page is a technical reference collection of radio frequency circuit diagrams spanning receivers, transmitters, and transceivers across a wide range of frequencies from 27MHz to 1GHz. Hobbyists and engineers will find schematics for superregenerative receivers, FM audio transmitters, walkie-talkies, SAW-based designs, and datasheets for chips from major manufacturers like Silicon Labs, HopeRF, and Texas Instruments.

Bitstream Technologies curates an extensive directory of electronics resources spanning circuit archives, DSP tools, embedded systems, robotics, PCB design, and IC information. A well-organized link library for engineers and hobbyists, covering everything from FPGA design tools to repair and test equipment references.

RED Free Circuit Designs is a hobbyist electronics resource offering dozens of free audio amplifier schematics, preamplifier modules, headphone amplifiers, and miscellaneous electronic circuit designs. Visitors can browse Class-A and Class-B amplifier projects, phono preamps, intercom circuits, and many more practical designs, all available at no cost.

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.