Module 14: Signals and Communication Basics

Every wireless device you own sends information by modulating a radio-frequency carrier: the AM and FM radio in your car, the television, your phone, Wi-Fi and Bluetooth, the key fob on your keyring, the contactless card in your wallet and the weather sensor on your fence. This module explains how that works — why information has to ride on a carrier at all, how amplitude modulation and frequency modulation encode a signal, and how digital modulation packs bits into amplitude, frequency and phase. It is the foundation for understanding, choosing and troubleshooting any wireless module or radio receiver you build into a project.

Module Overview

The module opens with the foundational question: why can't we just radiate audio or data directly as radio waves? The answer involves antenna physics and the need to share the spectrum, and it explains why every wireless system depends on a carrier and modulation.

The next two lessons treat the two classic analog modulations in depth. Amplitude modulation (AM) is the oldest and simplest, still used for broadcasting and aviation; you will learn how it creates sidebands, how its power is distributed, what overmodulation does, and how a simple diode detector recovers the audio. Frequency modulation (FM) trades bandwidth for noise immunity; you will learn about deviation, Carson's rule, the capture effect and pre-emphasis, and why FM broadcasting sounds so much better than AM.

The final lesson surveys digital modulation — ASK, FSK, PSK, QAM, OFDM and spread spectrum — the techniques inside Bluetooth, Wi-Fi, mobile phones, LoRa sensor networks and RFID tags, with constellation diagrams and a comparison of their bandwidth, power and noise performance.

Why This Module Matters

You do not need to design a radio to benefit from this module. Wireless modules are now among the most common components in electronics projects, and choosing between a 433 MHz OOK module, a LoRa module and a Bluetooth or Wi-Fi chip is a choice between the modulation methods described here — with very different range, data rate, power consumption and interference behavior. Understanding modulation also explains everyday puzzles: why AM radio buzzes near a switching power supply while FM does not, why Wi-Fi slows down as you move away from the router, and why some wireless links work through walls while others do not.

Lessons