Software Defined Radio
Listen to radio signals from around the world, explore the spectrum visually, decode digital transmissions and build your own flexible radio receiving station.
What Is Software Defined Radio?
Software Defined Radio, commonly called SDR, is a radio system where much of the tuning, filtering, demodulation and signal processing is performed by software instead of fixed analog circuits.
A small SDR receiver connected to a computer can behave like a shortwave receiver, scanner, aircraft receiver, spectrum analyzer, digital-mode decoder or remote monitoring station simply by changing software and antennas.
One Receiver. Many Possibilities.
SDR technology makes radio monitoring more visual, flexible and accessible than a traditional single-purpose receiver.
See the Spectrum
A live spectrum and waterfall display makes it easy to locate active signals across an entire band.
Receive Many Modes
Listen to AM, FM, narrow FM, SSB, CW and supported digital modes using compatible software.
Change Radios with Software
New software and plug-ins can add features without replacing the SDR receiver hardware.
Record Signals
Record normal audio or sections of spectrum for later playback, analysis and signal identification.
Operate Remotely
Connect an SDR to a home server or Raspberry Pi and access the receiver from another computer.
Decode Digital Data
Use compatible applications to decode APRS, ADS-B, weather data, amateur digital modes and other signals.
Live Online SDR Receivers
Public SDR sites allow you to control a remotely located radio receiver through a web browser. Choose a receiver near the signal you want to hear, select a frequency and begin listening.
KiwiSDR Network
Best for HFA worldwide directory of public KiwiSDR receivers. KiwiSDR is especially useful for amateur radio, shortwave broadcasting, utility stations and general HF listening.
- Worldwide receiver list and map
- Browser-based spectrum and waterfall
- AM, SSB, CW and narrowband reception
- Receiver availability varies by location
WebSDR
Multi-UserWebSDR servers allow multiple listeners to tune independently through a shared receiver. Many servers specialize in specific amateur bands or regions.
- Established public receiver directory
- Multiple simultaneous listeners
- HF, VHF and UHF coverage varies by server
- Excellent for checking band activity
Receiverbook
Search DirectoryReceiverbook combines listings for several kinds of browser-accessible receivers, including KiwiSDR, OpenWebRX and WebSDR installations.
- Search by receiver type
- Filter by frequency coverage
- Find HF, airband, VHF and UHF receivers
- Includes an interactive map
Linkfanel SDR Map
World MapAn interactive map that makes it easy to locate public receivers by geographic area. It is particularly useful for selecting a receiver close to a distant station.
- Map-based receiver selection
- Quick worldwide geographic search
- Useful for comparing propagation
- Dynamic KiwiSDR receiver information
OpenWebRX Receivers
Modern InterfaceOpenWebRX is a browser-based SDR platform used by many private operators and radio clubs. Receiverbook maintains a searchable list of public installations.
- Simple browser-based interface
- Supports multiple SDR receiver types
- Can include built-in digital decoders
- Coverage depends on the host station
OpenWebRX Project
Build Your OwnThe OpenWebRX project provides software for creating a browser-accessible SDR receiver at home, at a club site or at a remote radio location.
- Designed for remote web access
- Suitable for Raspberry Pi systems
- Works with several common SDR devices
- Useful for clubs and shared receivers
What Can You Receive?
Available signals depend on your SDR, antenna, location, local regulations, propagation and frequency coverage.
Amateur Radio
- HF voice and CW
- Local VHF/UHF repeaters
- FT8, FT4 and WSPR
- APRS data
- Amateur satellites
Aviation
- Airport tower
- Ground control
- Approach and departure
- ATIS information
- ADS-B aircraft data
Shortwave
- International broadcasting
- Time-signal stations
- Utility transmissions
- Weather information
- Long-distance amateur radio
Marine
- Marine VHF channels
- Weather broadcasts
- AIS vessel data
- Port operations
- Safety communications
Weather
- NOAA Weather Radio
- Weather satellite images
- Weather fax
- Emergency alerts
- Telemetry signals
Public Service
- Fire and EMS where available
- Public works
- Utilities
- Transportation systems
- Unencrypted systems only
Transportation
- Railroad communications
- Transit operations
- Commercial vehicle systems
- Telemetry
- Position-reporting data
Space
- International Space Station
- Amateur satellites
- CubeSats
- NOAA satellites
- Meteorological satellites
Home SDR Receiver Options
A home SDR can be as simple as an inexpensive USB receiver connected to a laptop or as advanced as an always-on remote receiving station with multiple antennas and receivers.
USB SDR and Computer
Connect an RTL-SDR-class USB receiver to a Windows, Linux or macOS computer. Install SDR software and connect an antenna appropriate for the frequencies you want to receive.
Higher-Performance Desktop SDR
Use an SDRplay, Airspy or similar receiver for improved filtering, sensitivity and dynamic range. This option is well suited to serious HF, VHF or UHF monitoring.
Raspberry Pi Remote Receiver
Connect an SDR to a Raspberry Pi and install OpenWebRX or another compatible server application. The receiver can remain on continuously and be accessed through your network.
Dedicated Mini PC Station
A compact Windows or Linux computer can support multiple SDR receivers, digital decoders, recording, remote desktop access and other monitoring software.
KiwiSDR Shared HF Receiver
Install a KiwiSDR-class network receiver with a suitable HF antenna. This creates a browser-based HF station that can be used privately or shared with other listeners.
Which SDR Setup Is Right for You?
Choose based on the bands you want to monitor, desired receiver performance and whether you need remote access.
| Setup | Experience | Primary Strength | Remote Access | Typical Role |
|---|---|---|---|---|
| RTL-SDR-Class USB Receiver | Beginner | Low-cost entry into SDR | Optional | General VHF/UHF monitoring |
| SDRplay-Class Receiver | Intermediate | Broad coverage and HF reception | Optional | HF through UHF station |
| Airspy-Class Receiver | Intermediate | Strong VHF/UHF performance | Optional | Serious local monitoring |
| Raspberry Pi + OpenWebRX | Intermediate | Low-power remote operation | Yes | Always-on network receiver |
| Dedicated Mini PC | Intermediate | Multiple applications and SDRs | Yes | Permanent monitoring station |
| KiwiSDR-Class Network Receiver | Advanced | Browser-based shared HF listening | Built In | Club or remote HF receiver |
Typical Home SDR Signal Path
The antenna and feedline are often just as important as the SDR receiver. Select every component for the frequency range you plan to monitor.
Simple Beginner SDR Station
A USB SDR receiver, suitable antenna and general-purpose SDR application provide an affordable way to begin exploring local radio signals.
- RTL-SDR-class USB receiver
- Windows, Linux or macOS computer
- SDR++ or SDR#-class software
- VHF/UHF antenna or discone antenna
- USB extension cable to reduce computer noise
- Optional broadcast-band filters
Responsible and Lawful Listening
Monitor only communications that may legally be received in your location. Do not attempt to defeat encryption, access protected systems, interfere with radio services or use intercepted information unlawfully. Receiving rules vary by country, state and type of radio service.
Start Exploring the Spectrum
You do not need to purchase equipment to experience SDR. Select a public receiver, choose a frequency and listen through your web browser.
Open the Worldwide SDR Map ↗