Non-Linear Junction Detectors (NLJDs)

Purpose & Principle — NLJDs are tools used to detect electronic devices by emitting high‑frequency RF signals and listening for harmonic responses (2nd/3rd) generated by semiconductor junctions within hidden electronics.

Detection Conditions — They work even when the target device is powered off or inactive, and can detect devices behind non‑metal barriers (like walls, furniture, luggage).

Key Specifications — Important specs include harmonic detection (2nd/3rd), sensitivity (in dBm), probe frequency range, antenna type (circular‑polarized), and power/output control.

Typical Applications — Used in Technical Surveillance Counter‑Measures (TSCM), secure facility sweeps, vehicle/parcel inspections, corporate espionage prevention, and forensic investigations.

Advantages — Ability to find hidden electronics silently (without emission trace), relatively quick sweep coverage of rooms/vehicles, and useful in pre‑occupancy or threat mitigation sweeps.

Limitations & Considerations — Operator skill matters a lot; metals/corrosion can cause false positives; barriers like thick metal or shielding reduce range; and local RF regulations must be considered.