QuadRF can spot drones and see WiFi through my wall

Original Article ↗ Hacker News Discussion ↗

Overall capabilities and use cases

  • Device is a 4.9–6.0 GHz, 4x4 MIMO phased‑array SDR that visualizes RF sources as AR “blobs” overlaid on camera images (“RF vision”).
  • Discussed uses:
    • Locating RF sources across large, complex structures (buildings, cars, aircraft).
    • Checking if specific antennas or MIMO elements are working, especially in hard‑to‑reach places.
    • Spotting Wi‑Fi / 5 GHz devices through walls; potentially hunting hidden cameras or undisclosed radios.
    • Prospective pre‑compliance / “soft‑run” EMC checks on site, though many argue traditional analyzers are better for single‑device testing.
    • Potential Meshtastic / mesh networking demos and phased‑array scaling (“MoonRF”) for larger systems.

Limitations and technical details

  • Narrow band: only 4.9–6 GHz. It cannot see 2.4 GHz Wi‑Fi, Bluetooth, sub‑GHz IoT, HF amateur bands, or 900 MHz / 400 MHz RC drones.
  • Detection angle appears relatively narrow; scanning the entire sky is non‑trivial.
  • Creator says receiver reaches within ~2 dB of thermal noise; several km drone detection is “easily doable” for strong consumer drones, but range is highly situational.
  • Frequency choice driven by compact antenna size and cost; lower bands would require larger arrays and more expensive RF front ends.
  • Custom 1‑bit-like ΣΔ ADC scheme via FPGA LVDS reduces cost and pin count; ~7–8 ENOB per ADC, with effective resolution improved by multi‑element averaging.
  • Multi‑tile synchronization and calibration rely on software and known calibration sources rather than a high‑end shared clock.

Drone detection and military context

  • Seen as one ingredient in counter‑UAS systems, but not state‑of‑the‑art; many airports already use multimodal radar/visual/acoustic/AI systems.
  • Hard problems remain: distinguishing drones from birds, detecting “dark” or fiber‑tethered drones, and coping with heavy jamming.
  • Some discuss using such arrays to localize jammers or operators; others note optical‑fiber‑controlled drones avoid RF detection.

Pricing and market position

  • Debate over early price expectations vs current ~$99 per RF tile / ~$500 for a 4x4 SDR; some see it as expensive, others as remarkably cheap for a hobbyist‑grade phased array.

Regulation, export controls, and ethics

  • Prior passive radar projects removed code over ITAR concerns; creator states QuadRF avoids radar functionality and has explicit US export classifications, with some countries/regions excluded.
  • Thread notes broad, somewhat ambiguous export‑control language and resulting self‑censorship.
  • People link this to wider trends: open source hardware/SDR outpacing government, commoditization of formerly “secret” phased‑array tech, and privacy concerns about “seeing through walls.”