The design generates an oscillator signal using the Pico's Programmable IO. For AM/SSB it uses the PWM output pins to generate an RF envelope which gets mixed together with the oscillator using an analog multiplexor. A small microphone is also connected to the Pico for voice transmissions. The designer notes that the output power is far too low to be used on the air, but adding an output amplifier would help.
The Raspberry Pi Pico is a low cost microcontroller board, and we note it cannot run Linux like standard Raspberry Pi boards. This means that software like RpiTX cannot be used.
In one of his latest videos Matt from the Tech Minds YouTube channel tests out the "Jstvro" handheld spectrum analyzer which can be found on sites like Banggood and Aliexpress (the device is cheaper on Aliexpress) for about US$127.50 for the single antenna model, and US$165 for the dual antenna model including shipping. The device appears to be a clone of the RF Explorer, which is a spectrum analyzer that has been on the market for several years.
A spectrum analyzer can be used to visualize the RF spectrum and find frequencies that are active. It cannot demodulate signals like an SDR.
The Jstvro spectrum analyzer covers 240-960 MHz on the first port and 15 - 2700 MHz on the second port, with a total visible bandwidth of anywhere between 112 kHz to 600 MHz. It comes with a single color illuminated LCD screen.
In the video Matt gives an overview of the spectrum analyzer and shows it operating. He notes that the USB-C connection to the PC does not appear to be working and Matt was unable to find the PC software or firmware updates mentioned in the manual. In the rest of the video Matt demonstrates the 2.4G WiFi analyzer feature, the spectrum analyzer feature and goes over the settings.
Visualize the RF Spectrum With This Handheld Spectrum Analyzer
Having worked on RF communications systems before, Damian knew that the same concepts apply no matter what the physical layer of communication is. His system called SDU-X uses two ultrasonic transducers mounted on 3D printed parabolic dish's to increase the directional gain, and an Arduino Nano with amplifiers and a Digital to Analog (DAC) converter for the ultrasonic transmission.
His post explains the hardware and protocol implementation, as well as explaining the Arduino code that he's released for free. The code and 3D printer models can be found on Thingiverse.
SDU-X: A software defined ultrasonic communications system.
DJI is a major manufacturer of consumer drones and their drones implement an RF protocol called DroneID which is designed to transmit the position of the drone and operator to authorized entities such as law enforcements and operators of critical infrastructure.
Recently the AntSDR team have managed to get DJI DroneID decoding working on the AntSDR's onboard ARM processor. The decoding software runs on board the AntSDR E200 and outputs decoded data via the serial or network port. The AntSDR E200 is an SDR that is based on the AD9361 chip and has a 70 MHz to 6 GHz tuning range, 56 MHz of bandwidth and 12-bit ADC. It has 2x2 full duplex TX/RX channels and has an onboard FPGA with ARM CPU core.
The update from AntSDR shows how to install the firmware onto the device and get it up an running. They note that drones that use Occusync 2 or 3 like the Mini2 or Mini3Pro work best, because other models may be encrypted or have a slightly different protocol which doesn't work with these decoders.
Aaron, creator of DragonOS has also uploaded a video showing the decoder in action.
Over on GitHub user Sultan-papagani has just released a modified RTL-SDR source for SDR++ that enables full manual control of the gain stages, filters and other features on R820T/2/R828D tuner based RTL-SDRs. This includes the Blog V3 and Blog V4. In the standard drivers many of these these features are automatically controlled.
Tweaking the individual LNA, Mixer and VGA gain stages manually can help you to maximize SNR, while adjusting the filters can help block out of band interference.
The modified source also enables the 'Hamonic reception' enhancement from the librtlsdr fork of rtl-sdr, which allows you to tune up to 6 GHz via harmonic mixing. Note that tuning above the standard maximum of 1.766 GHz will most likely require strong band pass filtering and an external LNA as the harmonic mode results in a lot of imaging and weak signals.
A new RTL-SDR Source for SDR++ with Manual Gain/Filter and Harmonic Mixing Controls
The RFNM is an upcoming software defined radio that will have eight 12-bit ADCs, up to 612 MHz real time bandwidth, and two DACs for transmitting with up to 153 MHz bandwidth.
The standard board will support tuning from 600 - 7200 MHz, with tuning expanded down to 10 MHz available via an RFFC2071A mixer daughterboard called Granita or Lime tuner daughterboard. The board also has an onboard VSPA DSP processor, as well as built in ARM CPU cores, and a 16 GFLOPS GPU all of which can help process the massive bandwidth, as that full live bandwidth will be very difficult to transfer and use on a PC.
Recently the RFNM team posted their End of December update, noting that they are currently testing revision 2 of their motherboard with revision 3 to be the production version. They also note that the Lime daughter board is ready for manufacturing, but the Granita daughterboard will be delayed until April. Everything else is estimated to be ready to ship by March.
The board has also now been redesigned to have a heatsink and fan. And they have managed to implement a Quadrature Error Correction kernel in their VSPA DSP processor. Finally, they are also drafting a plan to ship power calibrated daughterboards.
In one of his latest videos Matt from the Tech Minds YouTube channel has created a beginners guide to the HackRF and Portapack with the Mayhem Firmware. The HackRF is a popular affordable software defined radio with wide frequency range and transmit capabilities. An addon called the Portapack allows the HackRF to go portable, and custom firmware called 'Mayhem' significantly expands it's capabilities.
Matt uses a Chinese HackRF and Portapack clone set from Banggood which can be found very cheaply for around $200 shipped. The original Portpack can be found from the Sharebrained store for $200, and then original HackRF can be found form various resellers listed on the greatscottgadgets website.
In the video Matt unboxes the Portapack, shows an overview of the hardware and then goes on to show how to update the stock firmware to the Mayhem firmware. He then demonstrates a few of the capabilities of the Mayhem firmware.
Beginner's Guide To The HackRF & Portapak With Mayhem
This year there were several interesting stories and product releases that we posted about on the blog and this post will be a brief end of year review of some of our most popular posts. We also wanted to wish everyone a Merry Christmas and Happy Holidays to every celebrating at this time of the year!
In January we saw that the popular ADS-B Exchange (ADSBx) ADS-B aggregation platform was sold to a private equity firm called JETNET. This caused quite a bit of outrage as many involved with the development of the platform were blindsided by the owner's sudden decision to sell. ADS-B Exchange is a popular ADS-B aggregator that uses RTL-SDRs and is known for it's hard no censorship policy, allowing it to be used in projects like "Dictator Alert" and to uncover immoral use of aircraft in policing and military "kill chains". Many of the original team have since started a new service at https://airplanes.live.
ADSBExchange.com interface
Next in February at the height of the "Chinese Spy Balloon" scare we ran a story about how the US air force had shot down an amateur radio 'pico balloon' called K9YO-15 , on the assumption that it could have been another Chinese spy balloon. Pico balloons are party sized helium balloons with a solar powered amateur radio transmitter attached. The fun of the hobby is seeing how far and long around the world they can travel for. A typical pico balloon could circumnavigate the globe several times over several months, all whilst transmitting it's position.
Rough trajectory overlay
In April we saw the Flipper Zero go mainstream when it was reviewed on the Linus Tech Tips YouTube channel. The Flipper Zero is a small RF hacking device that gained high popularity on social media sites like TikTok.
Later in August we also released the RTL-SDR Blog V4 dongle, a limited edition RTL-SDR that makes use of existing stockpiles of R828D tuner chips. It has improved HF performance thanks to an upconverter, and improved filtering on the VHF and UHF bands.
