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:


    The 90s were a wonderful time for portable communications devices. Cell phones had mass, real buttons, and thick batteries – everything you want in next year’s flagship phone. Unfortunately, Zach Morris’ phone hasn’t been able to find a tower for the last decade, but that doesn’t mean these phones are dead. This weekend at Shmoocon, [Brandon Creighton] brought these phones back to life. The Motorola DynaTAC lives again.

    [Brandon] has a history of building ad-hoc cell phone networks. A few years ago, he was part of Ninja Tel, the group that set up their own cell phone network at DEF CON. That was a GSM network, and brickphones are so much cooler, so for the last few months he’s set his sights on building out a 1G network. All the code is up on GitHub, and the hardware requirements for building a 1G tower are pretty light; you can roll your own 1G network for about $400.

    The first step in building a 1G network, properly referred to as an AMPS network, is simply reading the documentation

  2. Tomi Engdahl says:

    A Dual Screen Luggable With Integrated RTL-SDR

    The latest of these cyberdecks, a dual screen “luggable” reminiscent of classic computers like the Compaq Portable or Kaypro, comes our way from [dapperrogue]. Powered by the Raspberry Pi 4 and featuring a scratch-built mechanical keyboard to perfectly fit the machines’s specific dimensions, this is easily one of the more practical builds we’ve seen.

  3. Tomi Engdahl says:

    Guido ten Dolle Turns the QCX CW Radio Kit Into an Arduino-Powered Single Side-Band Transceiver

    Designed to unlock new functionality, the upgrade kit adds an ATmega328 and a clever Arduino sketch to bring SSB capabilities to the QCX.

    Radio amateur Guido ten Dolle has released an open source, Arduino-powered upgrade for the popular QRP Labs QCX 5W continuous wave (CW) transceiver kit — turning it into a fully-functional, though experimental, Class-E single side-band (SSB) transceiver.

    The modification is part hardware, part software. The hardware side is an ATmega328 microcontroller, with an Arduino sketch loaded to sample the input audio and reconstruct the single side-band (SSB) signal by making small frequency changes via an I2C connection to a phase-locked loop (PLL). “In this way a highly power-efficient class-E driven SSB-signal can be realised,” ten Dolle notes. “A PWM driven class-E design keeps the SSB transceiver simple, tiny, cool, power-efficient and low-cost (ie. no need for power-inefficient and complex linear amplifier with bulky heat-sink as often is seen in SSB transceivers).”

  4. Tomi Engdahl says:

    This Crystal Radio Is Made From a Few Components and Old Credit Cards
    It’s not a Walkman. It’s a Visa.

  5. Tomi Engdahl says:

    How to Make a DIY Mini Cell Phone Tower Using Parts You Can Order Online
    But to get it to work long range might be pricy.

  6. Tomi Engdahl says:

    A dipole antenna is easy, right? Two wires, each a quarter wavelength long, emanate from a coax or other feedline. Unless it is an off-center dipole. The length is still the same, but you move the feed point to a different part. [KB9VBR] explains how this changes the antenna’s impedance from the nominal 70 ohms of a standard dipole.

    Why would you want to do that? The trick is to find a feed point that has acceptable impedance on multiple ham radio bands. Most automatic tuners can handle a certain range of mismatch so using an antenna like this with a tuner can allow one antenna to serve multiple bands with no traps or switches.

  7. Tomi Engdahl says:

    Evil Crow RF is a radiofrequency hacking device for pentest and Red Team operations, this device operates in the following radiofrequency bands:


  8. Tomi Engdahl says:

    If you live in a city it can be tricky to use a big ham radio antenna, but Becky Stern’s guide explains the process.

    How to Mount a Ham Radio Antenna on an Urban Rooftop

  9. Tomi Engdahl says:

    Printed in around 22 hours, this PETG loading coil is good for hundreds of watts — and uses less material than earlier designs.

    Tommy “SA2CLC” Stenmark’s 3D-Printed Vertical Antenna Loading Coil Is Clever, Compact, and Multiband

    Printed in around 22 hours, SA2CLC’s PETG loading coil is good for hundreds of watts — and uses less material than earlier designs.

    “I set up the antenna using a 6m fishing rod, [with] 2 radials, each 5m long. The radiator was cut to give good SWR at 20m with shorted coil, and then 30, 40 and also 60m could be matched using the coil.”

  10. Tomi Engdahl says:


    With the latest and greatest 5G cellular networks right around the corner, it can be difficult to believe that it wasn’t so long ago that cell phones relied on analog networks. They aren’t used anymore, but it might only take a visit to a swap meet or flea market to get your hands on some of this vintage hardware. Of course these phones of a bygone era aren’t just impractical due to their monstrous size compared to modern gear, but because analog cell networks have long since gone the way of the floppy disk.

    Eversberg] those antique cell phones may live again, even if it’s only within the radius of your local hackerspace. His software allows the user to create a functioning analog base station for several retro phone networks used in Europe and the United States, such as AMPS, TACS, NMT, Radiocom, and C450.

  11. Tomi Engdahl says:

    Turn Your PC Into a Low-Cost Satellite Ground Station for NOAA Weather Imagery

    A new guide on Public Lab walks Windows and macOS users through NOAA satellite imagery reception — and input is welcomed from Linux users.

    The guide is built around the use of low-cost, receive-only software defined radio (SDR) dongles – ranging from the popular RTL-SDR to more expensive devices like the AirSpy Mini and Funcube Dongle Pro+. These are combined with a circularly-polarised antenna and free software — SDR# for Windows users, CubicSDR for macOS users — to receive and later decode the transmissions.

    “The images transmitted by NOAA satellites are produced by the satellite’s primary scanning instrument called the Advanced Very High Resolution Radiometer (AVHRR),”

    “As the satellite passes over a given part of the earth, the AVHRR sensors collect and transmit data in near-real time. Think of the satellite as scanning Earth’s surface line by line. In the resulting images each pixel is approximately 4 × 4 km.”

  12. Tomi Engdahl says:

    Amateur radio has had access to dedicated—and increasingly valuable—chunks of spectrum for over a century. New technology is forcing changes in what operators are doing over the air.

    The Uncertain Future of Ham Radio

  13. Tomi Engdahl says:


    Amateur radio operators have always been at the top of their game when they’ve been hacking radios. A ham license gives you permission to open up a radio and modify it, or even to build a radio from scratch. True, as technology has advanced the opportunities for old school radio hacking have diminished, but that doesn’t mean that the new computerized radios aren’t vulnerable to the diligent ham’s tender ministrations.

    A case in point: the Kenwood TH-D74A’s firmware has been dumped and partially decoded

  14. Tomi Engdahl says:

    Raspberry Pi 4: How I built a software-defined radio system to track passing planes
    Build your own ADS-B flight data receiver and mapper.

  15. Tomi Engdahl says:

    W8WWV – Simple RF Current Probes

    If you want to be confident that your multi-element vertical array is operating as designed, it is essential that you measure the RF current magnitude and phase at each antenna element feed point. Simultaneous measurement of two elements using a dual-trace oscilloscope is particularly valuable because the magnitude and phase of each element is displayed. In the case of phased vertical arrays, what matters is the relative relationship between element current magnitude and phase, not their absolute values.

  16. Tomi Engdahl says:

    Open Source global network of satellite ground-stations

  17. Tomi Engdahl says:

    Welcome to CQ-DATV 86 which is now available as a free download from
    Lucien F1TE has news of Minitiouner changes with the ability to separate 14/18v on both NIM inputs.
    Trevor and Mike are still working on the Grass Valley panel and have added an OLED display and are planning a one off PCB run for the Vmix interface. So if you have a panel or looking to buy one in the future, “listen very carefully I will say this only once”. This will be a one off, pre order. Please don’t come back after the order has gone in, asking for a PCB. Contact [email protected]
    Three Reports from Jim KH6HTV, the first one on Hi Definition Digital ATV using the 5, 10 and 45 GHz bands.
    The second one on the NanoVNA network Analyzer, these Analysers were once the exclusive domain of the big boys and well outside Amateur prices, but at $50 “How could you go wrong”.
    Jim’s last report is on 70cms driver amplifiers and the use of CATV parts. Jim decided to build up a couple of amplifiers in Hammond die-cast enclosures (1590ABK) and see how well they would work for DVB-T. Lets not spoil it for you the full story is in this issue.
    Peter Cossins VK3BFG reports on the move of Vk3RTV after 40 years on the Victorian Education Department site at Olinda, the site has been lost and the equipment relocated
    Bill Eberle AB0MY and Don Nelson N0YE Have reported in the Boulder ATV news-letter on receiving DVB-T on a Raspberry Pi.
    One form the Vault is a USB to RS232 converter
    Please sit back and enjoy CQ-DATV 86 and accept our assurances that electronic magazines are 100% free from COVID 19 risks. If you are missing a back issue they are all in the CQ-DATV library along with the ATV handbooks

  18. Tomi Engdahl says:

    Modifying Consumer Off the Shelf Wireless LAN devices for specialized amateur use

    Since 1999 and possibly earlier, the US Department of Defense has used modified Consumer Off The Shelf (COTS) wireless LAN products reprogrammed to operate in military frequency bands with enhanced encryption. Most COTS WLAN products can be easily modified to employ these frequencies because of their modular architecture. Their future versions of modified COTS WLAN products may include frequency agile transceivers that can work in multiple frequency bands via plug-in modules or software selection.

    It’s a fact that most wireless devices are manufactured for international marketing. The manufacture just makes minor hardware or firmware changes to comply to the intended countries radio rules. These firmware options usually include minor output power and band plan changes.

  19. Tomi Engdahl says:

    Kinda reminds me of the old days running a PC on the floor to “intercept” DirecTV signals.

    How hackers could spy on satellite internet traffic with just $300 of home TV equipment

    Black Hat 2020: A researcher at Oxford University has demonstrated how he could gain access to sensitive information on corporate networks by targeting traffic being transmitted by satellites.

  20. Tomi Engdahl says:

    Flipper Zero — Tamagochi for Hackers

    Open source multi-tool device for researching and pentesting radio protocols, access control systems, hardware, and more.


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