CoronaSDR

RTL-SDR Client for iPhone and iPad

Turn your RTL-SDR dongle into a portable software-defined radio — listen to FM broadcasts, aircraft, marine, amateur radio, weather stations, and more from your iOS device.

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Requirements

• iOS 18.0+ on iPhone or iPad
• An RTL-SDR dongle connected to an rtl_tcp server on the same network

Features

Radio & DSP 6 demodulation modes: AM, NFM, WFM, USB, LSB, CW Squelch (AM, NFM) FM de-emphasis: 50 µs / 75 µs Configurable high-pass and low-pass audio filters BFO tuning for SSB and CW	Spectrum Display Real-time FFT spectrum analyzer Waterfall display GPU-accelerated rendering via Metal
Tuning & Control Frequency keypad, step buttons, and drag-to-tune Gain (auto/manual), PPM correction Direct sampling (Auto, Off, I, Q) Offset tuning, bias-tee toggle 4 performance profiles: Ultra Low to High sample rate	Station Management & Scanning Save favorites with tags CSV/TSV import and export List scan and range scan Dwell, hold, and skip via squelch
Playback & Integration Background audio playback Lock screen and Now Playing controls Deep link automation via coronasdr://	Diagnostics Live throughput (Mbps) IQ and audio buffer fill levels Overrun / underrun counters Network and audio quality indicators

Getting Started

1. Set up your RTL-SDR server

Connect your RTL-SDR dongle to a computer (Linux, macOS, Raspberry Pi, etc.) and start rtl_tcp:

rtl_tcp -a 0.0.0.0 -p 1234 -s 2400000

2. Connect from CoronaSDR

Open the app, enter the server's IP address and port (1234), and tap connect. The built-in connection test will verify everything works.

3. Start listening

Pick a mode, tune to a frequency, and you're on the air.

Running rtl_tcp as a System Service

For a persistent server (e.g. on a Raspberry Pi), create /etc/systemd/system/rtl_tcp.service:

[Unit]
Description=RTL-SDR rtl_tcp server
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
ExecStart=/usr/local/bin/rtl_tcp -a 0.0.0.0 -p 1234 -s 2400000
Restart=on-failure
RestartSec=2

[Install]
WantedBy=multi-user.target

Then enable and start it:

sudo systemctl enable --now rtl_tcp
sudo systemctl status rtl_tcp

Network Tips

• Keep your iPhone/iPad and the server on the same LAN/subnet
• Use wired Ethernet for the server whenever possible
• At 2.4 MSPS, IQ throughput is ~4.8 MB/s (~38 Mbps) — make sure your Wi-Fi can handle it

Deep Links

Automate CoronaSDR using the coronasdr:// URL scheme. Works from Shortcuts, Safari, or other apps.

Action	URL	Notes
Tune	coronasdr://tune?freq=100000000&mode=WFM	Tune to 100 MHz in WFM mode
Start	coronasdr://start	Start playback
Stop	coronasdr://stop	Stop playback

Parameters for tune:

Parameter	Required	Description
freq	Yes	Frequency in Hz (1000 – 4294967295)
mode	No	AM, NFM, WFM, USB, LSB, CW (case-insensitive)

Things to Listen To

Not sure where to start? Here are some popular frequencies:

Band	Frequency	Mode	What You'll Hear
FM Broadcast	88 – 108 MHz	WFM	Local radio stations
Airband	118 – 137 MHz	AM	Aircraft communications
2m Amateur	144 – 148 MHz	NFM / USB	Ham radio repeaters and simplex
ISS Downlink	145.800 MHz	NFM	International Space Station voice
Marine VHF	156.800 MHz (Ch 16)	NFM	Maritime distress and calling
NOAA Weather	162.400 – 162.550 MHz	NFM	Weather radio (US)
70cm Amateur	420 – 450 MHz	NFM	Ham radio UHF activity
ADS-B	1090 MHz	—	Aircraft position data (requires external decoder)

Tip: Frequencies vary by region. Check your local band plans for amateur radio and public safety allocations.

Feedback and Bug Reports

Found a bug or have a feature request? Please open an issue:

github.com/s1lviu/CoronaSDR/issues

When reporting a bug, include:

• iPhone/iPad model and iOS version
• RTL-SDR tuner type
• Server command line or service config
• Mode, frequency, and performance profile
• Steps to reproduce with expected vs. actual behavior

Support the Project

If you enjoy CoronaSDR, consider supporting its development:

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Made with 📻 by a ham radio enthusiast