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Emissions control

Summary

Emissions control (EMCON) is the deliberate management of a platform's electromagnetic and optical signature to reduce its detectability by hostile sensors. For civilian drone platforms operating in security-sensitive environments, EMCON means: minimising radio frequency emissions (reducing FPV VTX power or switching to relay-based operation, disabling non-essential broadcast), minimising optical signature (avoiding highly reflective surfaces in the visual spectrum, considering IR-dark configurations), and understanding what sensors can and cannot detect at what distances. The Ghost platform variant specifically addresses reduced-emissions operation. Full EMCON is operationally demanding — it trades capability for reduced detectability.

Concept

What can detect a small drone

Detection method Range (typical) Detects what EMCON countermeasure
Visual (eye) <200 m in open, much less in clutter Physical drone Dark colour, small size
Acoustic 50–300 m depending on noise floor Motor noise Lower RPM, electric motors already quiet
RF passive (spectrum monitor) 100s of m to km Active radio transmissions Reduce/eliminate RF emissions
Radar Depends on system — typically >1 km for dedicated C-UAS Physical size + motion Low radar cross-section, terrain masking
Infrared 100s of m for thermal systems Heat signature Manage waste heat, avoid hot surfaces
Remote ID receiver ~300 m Broadcast position Remote ID cannot be disabled for legal compliance

For civilian platforms, the most controllable signature is radio frequency. The FPV VTX is the largest deliberate RF emitter on the drone (25–800 mW at 5.8 GHz). The ELRS RC link is much lower power (10–100 mW at 2.4 GHz) but is still detectable by a sensitive spectrum monitor.

RF emission sources on libdrone

Source Frequency Power Controllable?
FPV VTX (HDZero) 5.8 GHz 25–800 mW Yes — switch SA on TX16S
ELRS RC link 2.4 GHz 10–100 mW (dynamic) Partially — dynamic power
Remote ID 2.4 GHz (WiFi NAN + BLE) <10 mW No — legally mandatory
ESP32-S3 payload WiFi 2.4 GHz <20 mW Yes — disable hotspot mode
ESC switching noise 48 kHz (radiated) Low Partially — twisted pairs help

Ghost platform reduced-emissions configuration

The Ghost variant is configured for minimum RF emission in security-sensitive deployments: - FPV VTX at 25 mW minimum power or disabled (relay-based operation) - ELRS dynamic power minimum set to 10 mW - Payload WiFi hotspot disabled during flight - Remote ID compliant (legally unavoidable) - Dark matte PETG finish reduces optical reflectivity

For fully relay-based operation (pilot not co-located with drone): the FPV feed is relayed via a separate encrypted link rather than direct 5.8 GHz transmission from the drone. This is a mission planning configuration, not a hardware change.

What EMCON does not hide

Motor noise is inherent to multirotor operation and cannot be eliminated without changing the fundamental propulsion system. A small drone at 50 m altitude is audible in a quiet environment. Electric motors are significantly quieter than combustion engines, but "electric = silent" is incorrect. At 20 m altitude, a 330 mm libdrone is clearly audible.

Radar detection depends on radar cross-section and system sensitivity. Small drones at low altitude in cluttered environments (tree lines, buildings) are difficult for non-dedicated radar systems. Dedicated C-UAS radars can detect small drones at ranges of hundreds of metres to several kilometres.

Reference

Emissions control operating modes

Mode VTX power ELRS power Payload WiFi When to use
Standard 200 mW Dynamic 10–100 mW On Normal operations
Low emission 25 mW 10 mW fixed Off Security-sensitive environments
RF-dark Off (relay only) 10 mW fixed Off Highest-risk deployments

Selecting the appropriate mode

Emissions control is a mission planning decision, not a default setting. For standard air quality mapping and civilian operations: Standard mode. For operations in proximity to sensitive sites, at night, or in security-relevant contexts: Low emission or RF-dark as appropriate.

Procedure

Switching to low-emission mode

  1. On TX16S, set VTX power switch (SA) to minimum (25 mW) position.
  2. In ELRS settings: set minimum power to 10 mW (already default).
  3. Disable ESP32-S3 WiFi hotspot mode in payload firmware before flight (set WIFI_HOTSPOT_ON_BOOT = False in config).
  4. Remote ID remains active — legally required.
  5. Brief the operation: low-emission mode reduces FPV link margin. Maintain closer range or accept shorter maximum range.

Rationale

Why emissions control is a Ghost/Bandit topic and not all-platform

Core and Pro are designed for civilian operations where RF emission is not a concern — in fact, maximum FPV video quality and link reliability are desirable. Emissions control is an operational mode for platforms deployed in security-sensitive contexts, which maps to Ghost (reduced-emission variant) and Bandit (autonomous resilience operations). Including emissions control considerations in the Core/Pro operational guidance would add complexity without operational relevance for those platforms' primary use cases.

Connections

requires: - iff-layers related: - remote-id-compliance - digital-fpv - elrs-protocol leads_to: - resilience-community