Show HN: RF Hunter – Find hidden cameras and other devices
A DIY tool called RF Hunter uses an ESP32 microcontroller and a broadband RF power detector to locate nearby wireless devices such as Wi‑Fi cameras, listening bugs, and phones by measuring their radio emissions. Commenters explore its capabilities and limits — noting that it works best on devices transmitting continuous data streams, is highly dependent on antenna choice and environment, and cannot detect fully passive or locally recording cameras. They also compare it with alternatives like thermal imagers, optical lens detectors, nonlinear junction detectors, and low‑cost spectrum analyzers, and debate what a fair price and design path would be for a commercial version.
Project overview & hardware
- Device uses an ESP32 to drive an LCD and read an RF power detector module (AD8317-based board).
- It’s point‑to‑point wired, no custom PCB; RF front-end handled by the detector module.
- Auto‑calibrates baseline RF level on boot and then shows relative increases in signal strength.
Cost, commercialization, and assembly
- BOM cost is reported around $30–$100 depending on source and pack sizes for parts.
- Several commenters say they’d pay $60–$150 for a pre‑assembled unit.
- Discussion of manufacturing economics: common “5× BOM” retail rule vs. skepticism that this applies cleanly to modular builds.
Detection capabilities & limitations
- Detects strong, sustained RF transmissions (Wi‑Fi/cellular cameras, phones, laptops) within tens of feet, depending on antenna and environment.
- Works well on continuous video or audio streams; poor at very short bursts or infrequent transmissions.
- Baselines out constant local Wi‑Fi; tends not to trigger on idle beaconing, but on active data transfers.
- Cannot detect non‑RF threats (e.g., passive cameras, wired recorders, people in closets).
- Sensitivity and range heavily depend on antenna tuning and local RF noise.
Use cases: hidden cameras, game cams, drones
- Intended uses: scanning Airbnbs, offices, and possibly detecting nearby drones.
- For trail/game cameras, many units store data locally or wake only briefly via PIR, making RF-only detection unreliable unless they use cellular modems.
Alternative and complementary detection methods
- Suggestions: thermal cameras (5 W devices stand out thermally), TinySA or SDRs for spectrum analysis, cheap “bug detectors,” optical lens detectors, and non‑linear junction detectors for powered‑off electronics.
- Smartphone IR-camera trick discussed; effectiveness varies by phone and IR wavelength.
Technical debates & RF nuances
- Some argue wideband directional detection is hard; ideas include log‑periodic antennas or phased arrays with AR visualization.
- One critic claims the design cannot “really scan”; others rebut that the analog detector needs no programming and works in practice.
- Multiple people stress that sophisticated implants using burst transmission or external excitation would evade this tool.