Software Defined Radio (SDR) category

Software-defined radio (SDR) is a radio communication system where components that have been traditionally implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system.

Experimenting with software defined radio used to be expensive, but now it is cheap. Nowadays it is very cheap to start experimenting with SDR. Most receivers use a variable-frequency oscillator, mixer, and filter to tune the desired signal to a common intermediate frequency or baseband, where it is then sampled by the analog-to-digital converter. Cheapest wide receiving range well working device is to use suitable DVB-T receiver stick (10-20 Euros/Dollars) and suitable software (very many alternatives, for example SDRsharp and Gnu Radio).

My article Software defined radio with USB DVB-T stick started the long list of SDR related postings. The newest postings now are Filter measurements with RF noise source and Antenna measurements with RF noise source.


  1. Tomi Engdahl says:

    (Ab)use an Arduino as AM Music Transmitter! © CC BY
    See how an Arduino can be transmit music over AM with only a few lines of code.

  2. Tomi Engdahl says:

    EmbedINN’s iotSDR Aims to be a One-Stop IoT Development Board for All Things Radio

    A Xilinx FPGA and two Microchip transceivers at its heart, the ioTSDR is certainly feature-packed — though there’s no sign of prototype yet.

    Pakistani IoT specialist embedINN is turning to crowdfunding to produce a development board aimed at communications projects, powered by a Xilinx Zynq FPGA and Microchip RF transceivers: the iotSDR.

    “It has two Microchip AT86RF215 frontends, capable of providing I/Q streams and modem functionality for the Xilinx ZYNQ SoC, as well as a MAX2769 GNSS chip for custom GPS, Galileo, BieDou, and Glonass development. It is also compatible with the popular GNURadio SDR software.

    “If you want to design and develop a physical layer protocol for IoT – a protocol like LoRa, Sigfox, WightLess, Bluetooth, BLE, 802.15.4, ZigBee, or something of your own — this board is for you. It is also a great place to start if you want to build a custom IoT gateway along the lines of The Things Network, LPWAN, or Google Thread.”

    The twin Microchip AT86RF215 transceivers support operation in a range of radio frequencies — 389.5-510 MHz, 779-1020 MHz, and 2400-2483.5 MHz – while the Maxim MAX2769B provides connectivity to global navigation satellite systems (GNSS) for position or timing

  3. Tomi Engdahl says:

    I did this almost a year ago with less than $200 of electronics to spoof gps

  4. Tomi Engdahl says:

    This website details the design and construction Wave Bubble: a self-tuning, wide-bandwidth portable RF jammer. The device is lightweight and small for easy camouflaging: it is the size of a pack of cigarettes.

  5. Tomi Engdahl says:

    Build a Long-Distance Data Network Using Ham Radio

    In 2013, I was looking at a protocol called NBP, used to create a data network over amateur radio links. NBP was developed in the 2000s as a potential replacement for the venerable AX.25 protocol [PDF] that’s been in use for digital links since the mid-1980s. I believed it was possible to create an even better protocol with a modern design that would be easier to use and inexpensive to physically implement.

    It took six years, but the result is New Packet Radio (NPR), which I chose to publish under my call sign, F4HDK, as a nom de plume. It supports today’s de facto universal standard of communication—the Internet’s IPv4—and allows data to be transmitted at up to 500 kilobits per second on the popular 70-centimeter UHF ham radio band.

    70-cm band permits long-distance links even when obstructions prevent line-of-sight transmissions.

    I turned to ISM (industrial, scientific, and medical) chips. These are transceivers designed to operate in narrow radio frequency bands that were originally allocated for noncommunication purposes, such as RF heating. However, the ISM band has become popular for communications as well because typically a license is not required for its use. In Africa, Europe, and North Asia, there is an ISM band lying inside the 70-cm ham radio band at 434 megahertz, so commercial ISM chips are available for this frequency.

    around the Si4463 [PDF] ISM transceiver: It’s cheap, flexible, and available in many modules and breakout boards

    widely available external 20-watt amplifiers for handheld radios designed for the European-developed Digital Mobile Radio (DMR) standard,

    The ISM transceiver is connected to an Mbed Nucleo STM32 L432KC microcontroller, which uses an Arm Cortex CPU.

    This microcontroller is in turn connected to an Ethernet interface, and it takes care of all the details of running the NPR protocol. Any connected PC or network sees the radio link as just another IPv4 connection with no need to install specific NPR software. The NPR modem can be configured over this link or via a USB connection. The total cost of the hardware is about US $80

    The NPR protocol is based on a hub-and-spoke model, in which a central modem links several client modems. Currently there can be as many as seven modems, although I plan to expand this to 15. The theoretical maximum distance between a client modem and the central modem is 300 kilometers. This limit arises because NPR uses a managed time-division multiple access (TDMA) technique

    NPR New Packet Radio
    IP over 430MHz Ham Radio, up to 500kbps, 20W RF.
    Extension for HSMM-Hamnet-AREDN. 100% open-source.

  6. Tomi Engdahl says:

    Tracking down a water leak with rtlamr

    An rtl-sdr receiver for Itron ERT compatible smart meters operating in the 900MHz ISM band.


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