SDR Direction Finder (RTL-SDR)

Working with Wildlife

About this app

SDR Direction Finder turns your Android phone and an RTL-SDR dongle into a precision VHF telemetry 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

Four selectable filter modes deliver real, measurable SNR improvements:

• Wide - general scanning and unknown frequencies
• Standard - SNR improvement, real detection range increase 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 RTL-SDR V3 and V4 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 visually even before they’re audible. Pinch-to-zoom spans from ±50 kHz to ±1 MHz. Full-screen landscape mode with live spectrum overlay. Drag-to-tune directly on the waterfall. Choose between Orange and Deep Blue colour schemes.

FIELD-OPTIMISED WORKFLOW

• Frequency presets for each tagged animal
• Configurable scan period for hands-free frequency cycling
• Physical volume buttons control receiver gain for one-handed field use
• Interactive onboarding walkthrough for new users
• Sample rate, FFT resolution, and waterfall colour scheme configurable for your hardware and preference

WHAT YOU NEED

• RTL-SDR Blog V3 or V4 dongle
• USB OTG cable
• Directional Antenna tuned to your tracking frequency
• Optional: external wideband 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.

What’s new

Improved hardware support
UI/UX Improvements
Bug fixes