Kiwi SDR: All You Need to Know About the Device

Introduction to KiwiSDR

KiwiSDR is a software-defined radio (SDR) device that allows users to remotely access and control a wide-band HF receiver from anywhere in the world via a web browser. Developed by John Seamons, ZL/KF6VO, the KiwiSDR is an open-source project that has gained popularity among radio enthusiasts, researchers, and educators.

The KiwiSDR is built around the BeagleBone Green (BBG) single-board computer and a custom cape that includes a 14-bit, 65 MHz analog-to-digital converter (ADC), a GPS receiver for time and frequency synchronization, and an Ethernet interface for network connectivity. The device covers a frequency range from 10 kHz to 30 MHz, making it suitable for a wide range of applications, including amateur radio, shortwave listening, and spectrum monitoring.

Key Features of KiwiSDR

Wide-band Coverage

The KiwiSDR offers a wide frequency range, covering 10 kHz to 30 MHz. This allows users to explore various segments of the radio spectrum, including:

• Long-wave (LW): 30 kHz – 300 kHz
• Medium-wave (MW): 300 kHz – 3 MHz
• Short-wave (SW): 3 MHz – 30 MHz

Within these bands, users can listen to a variety of broadcasts, such as international shortwave stations, amateur radio communications, and utility stations (e.g., maritime, aviation, and military communications).

Remote Access

One of the most significant advantages of the KiwiSDR is its ability to provide remote access to the receiver. Users can connect to a KiwiSDR device from anywhere in the world using a web browser, without the need for additional software or plugins. This feature makes it possible for multiple users to share access to a single receiver, fostering collaboration and educational opportunities.

Open-source Software

The KiwiSDR project is open-source, which means that the software and hardware designs are freely available for users to study, modify, and distribute. This openness encourages continuous development and improvement of the device, as well as the creation of custom applications and integrations.

The KiwiSDR software is built on a Linux-based operating system and uses a combination of C++ and JavaScript to provide the web-based user interface and signal processing capabilities. The source code is available on GitHub, allowing developers to contribute to the project and create custom extensions.

GPS Time and Frequency Synchronization

The KiwiSDR includes a GPS receiver that provides accurate time and frequency synchronization. This feature is essential for applications that require precise timing, such as time signal reception, frequency measurement, and direction finding.

The GPS synchronization also enables the KiwiSDR to participate in distributed networks, such as the KiwiSDR TDoA (Time Difference of Arrival) locator system. In this network, multiple KiwiSDR devices work together to determine the geographic location of a transmitter by comparing the arrival times of the signal at each receiver.

Waterfall Display and Spectrum Visualization

The KiwiSDR web interface includes a real-time waterfall display and spectrum visualization tools that allow users to visually identify and analyze signals within the received bandwidth. The waterfall display shows a scrolling history of the signal strength across the frequency range, with color-coding to represent signal intensity. This visualization makes it easy to spot intermittent or weak signals and observe changes in signal characteristics over time.

The spectrum display provides a snapshot of the signal power across the frequency range at a given moment. Users can adjust the bandwidth, center frequency, and other parameters to focus on specific portions of the spectrum and analyze signal properties such as bandwidth, modulation type, and signal-to-noise ratio.

Applications of KiwiSDR

Amateur Radio

KiwiSDR is a popular tool among amateur radio enthusiasts, as it allows them to remotely access and operate a wide-band receiver for various purposes, such as:

• Monitoring amateur radio bands for activity
• Participating in contests and special events
• Checking propagation conditions and identifying open frequencies
• Receiving and decoding digital modes, such as FT8, WSPR, and JT65

Amateur radio operators can also use KiwiSDR to experiment with antenna designs and compare the performance of different receiving setups by accessing remote receivers in various locations.

Shortwave Listening

Shortwave listening (SWL) is a hobby that involves tuning into international broadcasts, utility stations, and other transmissions in the shortwave frequency range. KiwiSDR is an excellent tool for SWL, as it provides access to a wide range of frequencies and allows users to listen to stations from around the world.

SWL enthusiasts can use KiwiSDR to:

• Explore international broadcast schedules and frequencies
• Monitor utility stations, such as maritime, aviation, and military communications
• Decode digital modes used by shortwave stations, such as RTTY, SITOR, and PSK31
• Participate in SWL contests and events

Education and Research

KiwiSDR is a valuable tool for education and research in the fields of radio science, electrical engineering, and telecommunications. Its open-source nature and remote access capabilities make it an ideal platform for teaching and learning about software-defined radio, signal processing, and antenna design.

Educators can use KiwiSDR to:

• Demonstrate concepts in radio technology and signal processing
• Provide hands-on experience with SDR hardware and software
• Facilitate remote learning and collaboration among students
• Conduct experiments and research projects related to radio propagation, interference, and spectrum monitoring

Researchers can leverage KiwiSDR to collect data from multiple locations, study ionospheric phenomena, and develop new algorithms for signal detection, classification, and geolocation.

Spectrum Monitoring and Interference Hunting

KiwiSDR can be used for spectrum monitoring and interference hunting, which involves identifying and locating sources of radio interference. This is important for maintaining the integrity of the radio spectrum and ensuring that licensed users can operate without disruption.

Spectrum monitoring applications of KiwiSDR include:

• Identifying and characterizing sources of interference, such as power line noise, lighting systems, and faulty electrical equipment
• Monitoring compliance with radio regulations and detecting unlicensed or unauthorized transmissions
• Collaborating with other KiwiSDR users to triangulate the position of interference sources using TDoA techniques

Government agencies, private companies, and amateur radio clubs can use KiwiSDR to establish distributed spectrum monitoring networks, share data, and coordinate efforts to mitigate interference.

KiwiSDR Hardware and Setup

Hardware Components

The KiwiSDR consists of the following main hardware components:

1. BeagleBone Green (BBG) single-board computer
2. Custom KiwiSDR cape with:
3. 14-bit, 65 MHz analog-to-digital converter (ADC)
4. GPS receiver for time and frequency synchronization
5. Ethernet interface for network connectivity
6. Enclosure and power supply
7. Antenna and coaxial cable

Setting Up a KiwiSDR

To set up a KiwiSDR, follow these general steps:

1. Assemble the hardware components, including the BBG, KiwiSDR cape, enclosure, and power supply.
2. Connect the Ethernet cable to the KiwiSDR and your local network router or switch.
3. Connect an antenna to the KiwiSDR using a coaxial cable with the appropriate connector (typically a BNC or SMA connector).
4. Power on the KiwiSDR and wait for it to boot up (this may take several minutes).
5. Access the KiwiSDR web interface by entering its IP address in a web browser.

Once the KiwiSDR is set up and accessible via the web interface, you can configure various settings, such as the receiver frequency, bandwidth, and demodulation mode.

Choosing an Antenna

The choice of antenna is crucial for achieving optimal performance with the KiwiSDR. The antenna should be designed for the frequency range of interest and have a good impedance match to the receiver.

Some common antenna types used with KiwiSDR include:

• Dipole antennas: Simple and effective for a wide frequency range, easy to build and install.
• Magnetic loop antennas: Compact and directional, good for reducing interference and noise.
• Active antennas: Incorporate a built-in preamplifier to improve sensitivity and reduce noise.
• Wideband antennas: Cover a broad frequency range, such as discone or log-periodic antennas.

When selecting an antenna, consider factors such as size, directivity, and compatibility with your local environment and regulations.

KiwiSDR Community and Resources

Online Forums and Discussion Groups

There is an active community of KiwiSDR users and developers who share knowledge, experiences, and support through various online forums and discussion groups. Some popular platforms include:

• KiwiSDR Forum: A dedicated forum for KiwiSDR users and developers to discuss hardware, software, and applications.
• KiwiSDR Mailing List: An email-based discussion group for KiwiSDR users and developers.
• Reddit: Subreddits such as r/RTLSDR, r/amateurradio, and r/shortwave often include discussions related to KiwiSDR and SDR in general.
• Facebook Groups: Groups such as “KiwiSDR Users” and “Software Defined Radio (SDR)” provide a platform for users to share information and ask questions.

Participating in these online communities can help you learn more about KiwiSDR, troubleshoot issues, and discover new applications and techniques.

Open-source Projects and Extensions

As an open-source project, KiwiSDR benefits from a vibrant ecosystem of user-contributed extensions, plugins, and integrations. These projects extend the functionality of KiwiSDR and adapt it for specific applications. Some notable examples include:

• KiwiSDR TDoA Extension: A plugin that enables KiwiSDR to participate in the KiwiSDR TDoA locator network for geolocation of transmitters.
• KiwiSDR Decoding Utilities: A collection of scripts and tools for decoding various digital modes and protocols using data from KiwiSDR.
• KiwiSDR Antenna Switching Extension: A plugin that allows users to remotely switch between multiple antennas connected to a KiwiSDR.
• KiwiSDR WebSDR Integration: Projects that integrate KiwiSDR with WebSDR, a web-based SDR receiver framework, to provide a unified interface for multiple SDR devices.

By exploring and contributing to these open-source projects, users can customize their KiwiSDR experience and collaborate with others to develop new applications and features.

Online Tutorials and Learning Resources

There are numerous online tutorials, guides, and learning resources available for KiwiSDR users of all skill levels. These resources cover topics such as setting up and configuring the hardware, using the web interface, and applying KiwiSDR for various applications. Some recommended resources include:

• Official KiwiSDR Documentation: The KiwiSDR website provides comprehensive documentation on setting up and using the device, as well as API references for developers.
• YouTube Tutorials: Many KiwiSDR users and enthusiasts have created video tutorials covering various aspects of using and developing with KiwiSDR.
• SDR Blogs and Websites: Blogs and websites dedicated to software-defined radio, such as RTL-SDR.com and SWLing.com, often feature articles and tutorials related to KiwiSDR.
• Online Courses and Workshops: Some educational institutions and organizations offer online courses and workshops that cover KiwiSDR and SDR technology in general.

By leveraging these learning resources, users can quickly get up to speed with KiwiSDR and explore its many applications and possibilities.

Frequently Asked Questions (FAQ)

1. What is the frequency range of KiwiSDR?

2. KiwiSDR covers a frequency range from 10 kHz to 30 MHz, which includes the long-wave, medium-wave, and shortwave bands.

3. Can multiple users access a single KiwiSDR simultaneously?

4. Yes, KiwiSDR allows multiple users to access the device simultaneously through its web-based interface. The number of concurrent users depends on the network capacity and server configuration.

5. Is KiwiSDR compatible with other SDR software, such as SDR#?

6. KiwiSDR is primarily designed to work with its own web-based interface. However, it is possible to use third-party software like SDR# with KiwiSDR by using virtual audio cables or network streaming protocols.

7. Can I use KiwiSDR for transmitting?

8. No, KiwiSDR is a receive-only device and cannot be used for transmitting. It is designed for receiving and analyzing radio signals.

9. What kind of antenna should I use with KiwiSDR?

10. The choice of antenna depends on the frequency range and application. Common antenna types used with KiwiSDR include dipoles, magnetic loops, active antennas, and wideband antennas such as discones or log-periodic antennas.

Conclusion

KiwiSDR is a powerful and versatile software-defined radio device that offers a wide range of applications for radio enthusiasts, researchers, and educators. Its open-source design, remote access capabilities, and active user community make it an attractive choice for anyone interested in exploring the world of radio technology.

By understanding the key features, applications, and resources available for KiwiSDR, users can unlock its full potential and contribute to the ongoing development of this innovative platform. As the SDR landscape continues to evolve, KiwiSDR is well-positioned to play a significant role in shaping the future of radio technology and enabling new discoveries and innovations in the field.