RF Interference and Noise

Overview

433 MHz is a shared ISM band. The SEARCH scanner measures RSSI, so it cannot tell a real beacon from a strong interferer - it only reports signal strength. Knowing the local noise floor keeps false hits from wasting a search.

Common Noise Sources

Source	Signal shape	How to tell
Car key fobs	Bursts on button press	Short, repeatable when you press your own key
Wireless weather stations	Periodic short packets	Regular cadence every minute
Tire pressure sensors	Short bursts as cars pass	Moves with traffic
Smart plugs / LED drivers	Broadband hash	Persistent, wide on the waterfall
Other LoRa/ISM devices	Variable	Check what neighbors use

Using SEARCH Threshold

The detection threshold (rssi, default -90 dBm) is your noise gate:

• Raise it (e.g., to -80 dBm) in noisy urban areas.
• Lower it toward -100 dBm only in quiet backcountry.
• Watch the RSSI baseline on a quiet channel first.

Checking the Noise Floor

1. Enter SEARCH mode on an unused frequency.
2. Note the idle RSSI over 30 seconds.
3. Compare against a known-quiet channel (e.g., one no one uses).
4. Set the threshold a few dB above the quiet baseline.

Real Beacon vs Interferer

A real Aegis-Beacon in SEARCH mode shows:

• A carrier keying in Morse (SOS pattern) at a stable frequency.
• RSSI that rises as you approach.
• The same frequency every TX cycle.

An interferer shows none of those patterns. If in doubt, look for the Morse signature before acting on a hit.

Related Pages

• SEARCH Mode
• Frequency Compatibility
• Troubleshooting RF
• Propagation and Range