Radio Basics for Complete Beginners

If you have never thought about radio before, this page gives you the mental model you need. No math, just concepts.

What a radio signal is

A radio signal is an electromagnetic wave, like light, but at a frequency your eyes cannot see. The beacon generates a wave at 433 MHz, meaning the wave oscillates 433 million times per second.

Frequency and wavelength

Frequency and wavelength are two ways of describing the same wave. Higher frequency = shorter wavelength. At 433 MHz the wavelength is about 69 cm. A quarter of that is about 17 cm, which is exactly why the beacon’s antenna is a 17.3 cm wire.

How the beacon transmits information

The beacon switches the carrier wave on and off in a pattern. Short on/off bursts are Morse dots, long bursts are dashes. A receiver that hears the carrier turning on and off can decode the pattern by ear or with software.

This is called CW (continuous wave) keying. It is the oldest digital transmission mode, and it is also the most robust: a simple carrier burst survives noise and weak signals far better than complex digital modulation.

Why this matters for rescue

Every digital system needs a decoder, a protocol, and often a network. CW needs only a receiver and a human ear (or a cheap SDR). That is the whole design bet of Aegis-Beacon: a rescuer with any scanner or SDR can hear your SOS and coordinates without any proprietary equipment.

Range in one sentence

Range depends on transmit power, antenna, and terrain. On flat line-of-sight terrain, the beacon reaches up to 15 km; in mountains with ridges in the way, expect much less, which is why beacon placement and search patterns matter.