Over on the Tech Minds YouTube channel Matt has recently showed us his build of DL5NEG's super simple diode based RF power sensor. The device is designed to detect and measure RF power, using a DC voltage meter and a calibration curve which converts the voltage detected by the diode into dBm. The simple diode based design is remarkably accurate, and could be a useful tool for testing or calibrating SDRs.
Matt's first build uses a simple copper PCB board, and although it is low precision the results he achieved match up pretty nicely with the calibration curves. In Matt's second implementation he created a proper PCB design using KiCad and PCBWay. After soldering the components with hot air, he found that the results were just as good when he tested the power output of his AntSDR E200.
Matt intends to use this sensor along with a simple ADC connected to a Raspberry Pi to measure the power going into his QO-100 setup via a -40 dBm coupler.
DCF77 is a long wave time keeping signal transmitting at 77.5 kHz from Frankfurt, Germany. It has been active since 1 January 1959. Using simple amplitude modulation, the signal encodes the current time and date, which is used by some devices like railway station clocks in Germany. Because it's a long wave signal transmitting at 50kW, it's possible to receive the signal across Europe, and sometimes even further away if propagation conditions are good.
Currently the decoder has been tested to work with an Airspy HF+ Discovery SDR, but it should work with any SDR capable of receiver 77.5 kHz if the GNU Radio source block is changed out.
PySDR is a free online textbook created by Dr. Marc Lichtman which explains many digital signal processing (DSP) and software defined radio (SDR) concepts in a clear, concise and easy to understand way. The guide includes multiple images and animations, as well as Python code examples.
Direction-of-Arrival (DOA) within DSP/SDR refers to the process of using an array of antennas to estimate the DOA of one or more signals received by that array. Once we know the direction a signal of interest is arriving from, we can isolate it from other signals/interference/jamming.
It is just like isolating a signal in the frequency domain by filtering it, except we are now working in the spatial domain (you can certainly combine both!).
We typically refer to the antennas that make up an array as elements, and sometimes the array is called a “sensor” instead. These array elements are most often omnidirectional antennas, equally spaced in either a line or across two dimensions.
DOA is a subset of beamforming techniques, where as the receiver, we are trying to steer a beam (our receiver’s antenna beam) towards the direction of an emitter. We may also steer a beam blindly across a wide range (e.g., 0 to 360 degrees) to figure out what signals are being received and from what direction.
A visual example of what happens to two signals when the interelement spacing of a direction finding antenna array is reduced below half a wavelength.
Over on YouTube we've found an interesting project by RingingResonance where he's created a simulated traditional radar scope using a real analog radar scope tube, and ADS-B data gathered from an RTL-SDR running dump1090 on a Raspberry Pi 3B.
The project uses a real radar scope tube which is controlled by SPI signals sent from the Raspberry Pi into a DAC, which is in turn connected to the analog radar scope. RingingResonance has uploaded the open source code to GitHub. He notes that the code currently pushes the Raspberry Pi 3 to it's limits, so the sweep speed is limited.
It was to be a US$149 FT8 receiver based on an open source RF chip design, capable of acquiring signals between 7 MHz and 70 MHz (technically 1 MHz to 100 MHz). Shipments were expected to begin in April 2023.
Unfortunately the Maverick team just released today that the project will be suspended indefinitely due to logistical issues. Backers of the project will receive a full refund.
The Maverick-603 project has been indefinitely suspended due to unforeseen logistical obstacles. No funds have yet been spent and all backers will receive full refunds. If you backed this project, your refund will be issued within the next week to the credit card you originally used. If your credit card is no longer valid, please contact Crowd Supply support before midnight UTC on Friday, April 28, 2023 to arrange your refund. If the Maverick-603 project is revived, we will post another update. Thank you for your support and patience.
The RFNM is an upcoming software defined radio that has some impressive high end specifications only seen in SDRs costing thousands, and at the same time the creator claims that it will be priced at a steal. While no pricing has been set, the creator noted in a Reddit post that pricing will be "closer to $500", bringing it's price similar to SDRs like the HackRF, bladeRF, LimeSDR, PlutoSDR.
The RFNM will have eight 12-bit ADCs on board, and provide up to 612 MHz of real time bandwidth for receiving. For transmitting it has two DACs, with up to 153 MHz of TX bandwidth. The tuning range will be from 10 MHz up to 7200 MHz. They note that their front end also has 13 preselection filters and six different LNAs and programmable attenuators.
Pushing 12-bit 612 MHz bandwidth of the device would be difficult, so to help with processing all that data, there will be an onboard VSPA DSP processor, as well as built in ARM CPU cores, and a 16 GFLOPS GPU. Connectivity will be either through USB 3.0, or Ethernet.
The main baseband chip on the SDR is the Layerscape® Access LA9310 chip sold by NXP which provides I/Q ADCs and DACs. Those signals are sent to the RFNM Daughterboard Interface, where they are upconverted to the frequency range of interest. This lets the end user choose a different daughterboard for different applications.
The Granita daughterboard has tuning capability from 600 MHz to 7200 MHz. To get frequencies down to 10 MHz the RFNM is making use of the RFFC2071A mixer. There will also be a cheaper 'lite' version that does not use a mixer, and hence only provides tuning from 600 MHz to 7200 MHz.
In addition, the website states that they are pursing a version of their board that will make use of the LimeSDR LMS7002 chip that will cover 10 MHz to 3500 MHz. They are also looking into boards that may break out more ADC lanes, an oscilloscope add-on, and breakout board.
You can join the RFNM email waiting list, and find more details about it at rfnm.io. At the time of this post they state that the waiting list is "53% full". As of right now the project appears to have nothing concrete to show off, but the lead creator Davide Cavion was behind the FPV Blue HD Video system, so he appears to have the experience to take this project forward.
A render of the RFNM software defined radio board.
Just yesterday we posted about Linus Tech Tips review of the Flipper Zero. In related recent news, Flipper Zero was also banned from Amazon for being a "card skimming device". While the Flipper Zero reading the public NFC data from credit cards, it doesn't seem like it could do much more than what an Android phone could do with an NFC credit card reader app. Anyone skimming credit cards would still require the CVV code and other address details in order to put through a transaction.
This comes along from a bad string of events that has hit the Flipper Zero team. A while back PayPal froze 1.3M of its cash, requiring them to retain lawyers to force PayPal to partially release the funds. US customs then proceeded to seize its US bound shipment for inspection, then to throw salt in the wound, after releasing the goods they were billed $70,000 in storage fees for the pleasure of requiring inspection.
There are also reports of eBay banning the sale of Flipper Zero devices citing 'hacking' devices not being allowed on their platform.
The Brazilian National Telecommunications Agency has also begun seizing imports of Flipper Zero devices.
Flipper Zero is an affordable handheld RF device for pentesters and hackers. It is not based on SDR technology, however it uses a CC1101 chip, a digitally controlled RX/TX radio that is capable of demodulating and modulating many common digital modulations such as OOK/ASK/FSK/GFSK/MSK at frequencies below 1 GHz.
The CC1101 chip has been around since 2007, and there are many similar devices making use of the chip. However, the Flipper Zero is specifically marketed as a pentesting and hacking device, and provides built in software for doing things like replay attacks.
Part of the problem with the bans may also be the huge popularity that the device has received. The device has become exceedingly popular on social media sites like TikTok where users often show it being used mischievously.
Flipper Zero remains available for sale on its website flipperzero.one, for US$169.
The Flipper Zero is an affordable handheld RF device for pentesters and hackers. It is not based on SDR technology, however it uses a CC1101 chip, a digitally controlled RX/TX radio that is capable of demodulating and modulating many common digital modulations such as OOK/ASK/FSK/GFSK/MSK at frequencies below 1 GHz.
What sets it apart from most of the other CC1101 devices is the high level of software support built into it, the enthusiastic community and of course the branding.
Back in August 2020 we initially posted about the Flipper Zero starting its crowdfunding campaign on Kickstarter. Since then, despite major business problems like PayPal freezing 1.3M of its cash, and US customs temporarily seizing its shipments, then passing a $70,000 bill on to them for storage fees, Flipper has gained huge popularity through social media video sites like TikTok, where people show off its capabilities, often in ways that could be considered mischievous.
Recently over on YouTube, Linus from the most popular technology YouTube channel Linus Tech Tips reviewed the Flipper Zero. In the video Linus discusses the legally and morality of the Flipper Zero, and discusses some use cases around RFID and NFC.
