Decoding 433 MHz radio signals

Analyzing 433 MHz radio signals from common wireless devices, such as temperature sensors and remote controls, involves understanding On-Off Keying (OOK) modulation. This resource details the process of capturing these signals using a Software Defined Radio (SDR) like Gqrx and then visually inspecting the captured audio data in a sound editor such as Audacity. It differentiates between Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM) encoding schemes, illustrating how to identify and decode binary data by eye based on pulse and gap durations.

The article provides a step-by-step walkthrough for decoding a wireless thermometer's data, correlating bit patterns with known temperature, humidity, and channel values. It also demonstrates decoding an RF remote control's button presses, highlighting the constant and varying parts of the transmitted packets. The content further introduces automated decoding using tools like RTL433, explaining its capabilities in parsing various device protocols and showing how to interpret its output, including modulation type and decoded data.

Specific examples include analyzing Prologue sensor protocol specifications from RTL433's source code and noting common operating frequencies like 433.92 MHz in Europe and 915 MHz in the US.