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[updated 10 July 2024]

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KiwiSDR

Software-defined Radio (SDR) and GPS for the BeagleBone

An add-on board ("cape") that turns your BeagleBone into a web-accessible shortwave receiver.

Details

• Listen live: List, Map
• Online Store
• Project webpage
• Operating information: installation, operation, FAQ
• User Forum
• Latest source code commits
• Design review document
• KiwiSDR 1 Schematic
• KiwiSDR 2 Schematic

Description

This SDR is a bit different. It has a web interface that can be used by up to four separate listeners. Each one listening and tuning an independent frequency simultaneously. See the screenshots below.

Components

• SDR covering the 10 kHz to 30 MHz (VLF-HF) spectrum.
• Web interface based on OpenWebRX from András Retzler, HA7ILM.
• Integrated software-defined GPS receiver from Andrew Holme's Homemade GPS Receiver.
• LTC/Analog Devices 14-bit 65 MHz ADC.
• Xilinx/AMD Artix-7 A35 FPGA.
• Maxim/Analog Devices MAX2769B GPS front-end.
• Kiwi board works with BeagleBone Green, Black, BBAI or BBAI-64.

Features

• Open Source.
• Browser-based interface allowing multiple simultaneous user web connections.
• Each connection tunes an independent receiver channel over the entire spectrum.
• Waterfall tunes independently of audio and includes zooming and panning.
• Multi-channel, parallel DDC design using bit-width optimized CIC filters.
• Built-in signal decoding: ALE CW DRM FAX FSK FT8 HFDL IBP NAVTEX/DSC SSTV TDoA WSPR and more.
• Good performance at VLF/LF since we personally spend time monitoring those frequencies.
• Automatic frequency calibration via received GPS timing.
• Easy hardware and software setup. Browser-based configuration interface.
• KiwiSDR 2 features:
  • Reverse proxy service enabled by default to ease network installation.
  • 0 - 31.5 dB electronic attenuator.
  • External ADC clock input.
  • Built-in self test for checking the RF path.
  • 5V input reverse polarity protection.

Status

Give the live receivers a try at the links above. You'll need a recent version of a modern web browser that supports HTML5. The web interface works, with some problems, on mobile devices. But there is no mobile version of the interface yet.

A second generation device, the KiwiSDR 2, is now in production.

Objectives

We wanted to design an SDR that provides certain features, at a low price point, that we felt weren't covered by current devices. The SDR must be web-accessible and simple to setup and use. We also wanted to provide a self-contained platform for experimentation with SDR and GPS techniques. The TDoA extension is an example.

Most importantly, we wanted to see a significant number of web-enabled, wide-band SDRs deployed in diverse locations world-wide because that makes possible some really interesting applications and experiments. Over 700 Kiwis are publicly available currently.

Operation

Users can purchase just the KiwiSDR board or a complete unit consisting of the board, BeagleBone Green (software pre-installed), enclosure, and GPS antenna (see here). The software will try to automatically open up an incoming port through whatever Internet firewall/router may exist on the local network, but the user may have to perform this step manually. A reverse proxy service is available.

An antenna solution must be provided. An adequate power supply (e.g. 5V @ 2A) will also be required.

Four channels of audio and waterfall streamed over the Internet 24/7 requires about 30 GB per month. This is a common cap for many residential broadband plans. An automatic dynamic-DNS system is already part of the software so a web link to the SDR is immediately available with no configuration. Of course the system can be configured to only allow connections from the local network and ignore Internet connection requests.

Web interface and built-in signal decoder screenshots:

Click images for full size.

Not many SDRs can show the entire 10 kHz to 30 MHz spectrum at one time.

Waterfall/spectrum has 15 levels of zoom (z0 - z14).

Here is z14 (2 kHz span) on the left showing the 25 Hz sweep rate of an Over the Horizon Radar (OTHR) which is very helpful with signal identification. On the right is z10 showing the full passband.

The Kiwi is excellent at VLF/LF reception.

Especially with the right antenna and after eliminating noise sources. When you zoom in further the labels below the spectrum clearly identify all these signals.

High frequency trading signal on left, CQWW RTTY DX contest on right.

The Kiwi has built-in decoders for various ham radio and shortwave signals.

Here is ham slow-scan television decoding.

Ham FT8 mode on 30 meters.

Note FT8 pileup 3 kHz below working YJ0TT Vanuatu.

Digital Radio Mondial (DRM), including image slideshow and Journaline text decoding.

Time Difference of Arrival (TDoA) signal direction finding.

Multiple Kiwis, assisted by their built-in GPS for accurate timing, can cooperate to approximately locate signals. LF time station DCF77 77.5 kHz in Germany accurately located.

High Frequency Data Link (HFDL) decoding.

Aircraft to ground station (green) data exchange system. Includes message decoding and aircraft positions (blue) on a map.

Facimile (FAX) decoding.

Frequency shift keying (FSK, RTTY) decoding.

Other decoders:

IQ display showing the QPSK modulation of VLF station NLM4 North Dakota (25.2 kHz) as received in Kansas.

Decoding of time station WWVB (60 kHz, phase modulation) in Colorado.

When the Russian VLF Alpha navigation system is active there's a special decoder for that too.

A simple monitor for the Loran-C and under-development eLoran system. A recent West Coast USA eLoran test shown here.

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