Module 3: Basic Electronic Components

Every radio — from the simplest crystal set to a modern software-defined transceiver — is built from a handful of fundamental components. This module introduces each one: what it does, how it works, how to identify it, how to calculate its behavior, and where you will find it in radio circuits. By the end, you will be able to pick up a component, identify it, look up its datasheet, and understand its role in any schematic you encounter.

Module Overview

Electronic components fall into two broad categories: passive components (resistors, capacitors, inductors, transformers) that store or dissipate energy but cannot amplify it, and active components (diodes, transistors, ICs) that can control or amplify electrical signals using an external power source.

This module covers all the key components you will encounter when reading radio schematics, building kits, or repairing equipment. Each lesson follows the same structure: what it is, how it works, how to identify and measure it, its key parameters, the relevant formulas and calculators, and its specific applications in amateur radio.

Passive Components

Resistors oppose current flow. They set gain, divide voltages, limit current to LEDs and meters, and terminate transmission lines. Capacitors store charge in an electric field, block DC while passing AC, and tune circuits in combination with inductors. Inductors store energy in a magnetic field, oppose changes in current, and form the inductive half of every tuned circuit and RF filter. Transformers use magnetic coupling to change voltage levels, provide isolation, and match impedances.

Semiconductor Devices

Diodes are one-way valves for current — the foundation of rectification and signal detection. Special diodes (Zener, Schottky, varactor, PIN) exploit the P-N junction in different ways for regulation, fast switching, voltage-controlled tuning, and RF switching. LEDs emit light when forward-biased and need a current-limiting resistor. Bipolar junction transistors (BJTs) amplify current and switch signals. Field effect transistors (JFETs and MOSFETs) are voltage-controlled devices with very high input impedance, used in low-noise preamplifiers and power switching. Integrated circuits pack complete functional circuits — amplifiers, regulators, microcontrollers, synthesisers — into a single package.

Electromechanical and Power Components

Relays are electrically operated switches that provide galvanic isolation between control and load circuits — essential for antenna switching and T/R switching. Switches and fuses provide manual control and overcurrent protection respectively. Batteries power portable and emergency stations, and their chemistry, capacity, and charge characteristics determine runtime and suitability for the application.

Lessons