RF Basics for the Beacon
Edit on GitHubdBm, RSSI, CW vs OOK, and the vocabulary used across this wiki
RF Basics for the Beacon
Overview
A working knowledge of a few RF concepts makes every other page in this wiki clearer. This page defines the terms used throughout the documentation.
dBm
Decibels relative to 1 milliwatt - the unit for TX power and received signal strength.
| Level | Example |
|---|---|
| +30 dBm | E22 PA maximum |
| +22 dBm | RadioLib cap |
| +17 dBm | Default TX power |
| -60 dBm | Strong received signal |
| -90 dBm | Weak signal near the threshold |
| -120 dBm | Sensitivity floor |
Rule of thumb: every +3 dB doubles the power. +17 to +30 dBm is a factor of ~20 in power - the reason EMERGENCY transmits at max.
RSSI
Received Signal Strength Indicator - how strong a signal arrives at the receiver. The SEARCH mode measures it per frequency and maps it to audio pitch and OLED bars.
CW vs OOK
| Modulation | What happens |
|---|---|
| OOK | Carrier turned on/off (on-off keying) |
| CW | Continuous wave keyed on/off |
The SX1262 does not support true OOK, so the firmware keys a continuous FSK carrier with transmitDirect()/standby(). Receivers cannot tell the difference: it is Morse either way.
ISM Band
433 MHz is an unlicensed ISM (industrial, scientific, medical) band in most of the world, with power limits that vary by region. See Regulatory Compliance.
Link Budget
TX power + antenna gains - path losses = received signal. If that beats the receiver threshold, you have a link. See RF & Link Budget.