SDR Direction Finder (RTL-SDR)

SDR Direction Finder turns your Android phone and a low-cost SDR dongle into a precision radio receiver and direction finder. Purpose-built for weak signal detection across the full RTL-SDR frequency range with wildlife tracking in mind. Whether you are a field researcher tracking tagged animals, a falconer monitoring transmitter collars, a ham radio operator hunting hidden transmitters, or an RTL-SDR enthusiast pushing sensitivity limits, SDR Direction Finder delivers narrow-band DSP filtering, a live waterfall display, and a full GPS bearing map in a package that fits in your pocket. PURPOSE-BUILT SIGNAL PROCESSING Multiple demodulation modes: CW (default for wildlife tracking), AM, FM, FM-B (wideband FM broadcast with Mono and Stereo options), LSB, USB. Fast native DSP engine with squelch, AGC, manual gain and PPM correction. Four selectable filter modes deliver real, measurable SNR improvements: • Wide - general scanning and unknown frequencies • Standard - Real SNR improvement for CW/LSB/USB • Narrow - Further SNR improvement for precisely known frequencies • Extreme - Maximum filtering for precisely-tuned CW frequencies COLLAR DETECTION MODE Finds beacons even when you can't hear them. Collar Detection Mode visually reveals faint signals buried deep in the noise, extending your detection range beyond what your ears can pick out of the static. Calibrate once per collar, choose a detection level from 1 to 5, and watch the screen. BEARING MAP - DIRECTION FINDING ON THE GO • GPS overlay with live compass cone showing your heading • Log compass bearings from multiple positions with one tap • Automatic intersection calculation estimates the signal source location • POI markers for receiver positions and landmarks • Street, Satellite, and Terrain map tiles • Offline map download for remote fieldwork • KMZ/KML file support for existing survey data • Scale bar, zoom controls, track recording, and screen lock • Import/Export saved bearings, POIs, and tracks to transfer between multiple devices or to open in Google Earth, QGIS, Excel, R, Python or any other tool that handles tabular data. BIAS-TEE LNA POWER CONTROL For supported dongles, the built-in software-controlled bias-tee sends 4.5V down the coax to power a masthead LNA directly from the app, with no separate power cable needed. LIVE WATERFALL DISPLAY See signals before you hear them. Fullscreen landscape waterfall with live spectrum overlay, pinch-to-zoom span, drag-to-tune and 100 Hz fine-tune buttons. Choose between Orange and Deep Blue colour schemes. SIGNAL STRENGTH TONE An optional tone whose pitch rises with signal strength - the classic ARDF technique. SIGNAL mode follows continuous transmitters while PULSE mode holds each beacon pulse's pitch. FIELD-OPTIMISED WORKFLOW • Frequency presets for each tagged animal • Configurable scan period for frequency cycling • Physical volume buttons control receiver gain for one-handed field use • Interactive onboarding walkthrough for new users • HF, VHF and UHF coverage, hardware-dependent. WHAT YOU NEED • RTL-SDR, Nooelec, Airspy, or HackRF dongle. • USB OTG cable • Directional Antenna tuned to your tracking frequency • Optional: LNA for additional sensitivity gain (required for bias-tee power delivery) and/or a Bandpass filter. IDEAL FOR • Wildlife tracking or Falconry & VHF telemetry research • Ham radio fox hunting and hidden transmitter direction finding • RTL-SDR enthusiasts pushing weak-signal sensitivity limits • Field researchers needing multi-frequency awareness & bearing logging • Graduate students & NGOs needing affordable telemetry alternatives No ads. No tracking. No data collection. Developed for Working with Wildlife (workingwithwildlife.org) for conservation and the radio community. © 2026 Working with Wildlife. All rights reserved.