RF Power Snitch: RF Power Measurement Companion for Protecting RF Equipment

Thank you to Majodi Ploegmakers who wrote in and wanted to share a product he's created that might be useful for some RF enthusiasts. The product is called the "RF Power Snitch", and is a tool used to quickly measure RF input power to determine if input power from a signal source is too strong and could damage measurement equipment such as an SDR or NanoVNA. The product is not yet for sale, but Majodi has an availability notification signup page.

NickStick Design Announces - RF Power Snitch –
“Your RF Measurement Companion”

The Netherlands: Today, NickStick Design, an electronics design company for Makers, announced their RF Power Snitch. After a successful launch of SwarmDrive through Crowd Supply last year, NickStick Design went on and designed another useful tool for makers in the RF (Radio Frequency) domain this time.

Of the company’s recent crowd funding campaign, Majodi said, “We were very pleased with the interest our last, somewhat niche, product received. It spurred us on to develop and realize our next idea”.

Today, the RF domain has become accessible to everyone through affordable tools that many could only dream of before. The only tool missing though, is a simple device for checking the, potential, destructive power of the signals one would want to analyze. Because, although tools like the TinySA, NanoVNA or SDR devices are extremely affordable today, for a maker it is still an investment worth protecting.

That’s why our goal was to develop a low-cost companion device that can help makers and experimenters (especially beginners) in the RF domain to gain insight in the power levels of a signal before hooking things up to their valuable test equipment. As an extra to this we also made it possible to attach an MCU for doing power readings and plotting.

Website: https://powersnitch.nickstick.nl

The RF Power Snitch
The RF Power Snitch
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Sparse Array Beamforming with a Phase Coherent 21-Channel RTL-SDR Array

Thank you to Laakso Mikko a PhD student at Aalto University School of Electrical Engineering for submitting news about his research group's latest paper involving a 21-channel phase coherent RTL-SDR system. Laakso writes that he an his colleagues have built a (massive) multichannel receiver array from RTL-SDRs to use in low-budget research. The paper presented at EUSIPCO2020 can be found at IEEE, and for free on their research portal (direct pdf link). The code is also entirely open source and available on GitHub.

Phase coherent SDRs enable interesting applications such as radio direction finding (RDF), passive radar and beam forming.

We introduce a modular and affordable coherent multichannel software-defined radio (SDR) receiver and demonstrate its performance by direction-of-arrival (DOA) estimation on signals collected from a 7 X 3 element uniform rectangular array antenna, comparing the results between the full and sparse arrays. Sparse sensor arrays can reach the resolution of a fully populated array with reduced number of elements, which relaxes the required structural complexity of e.g. antenna arrays. Moreover, sparse arrays facilitate significant cost reduction since fewer expensive RF-IF front ends are needed. Results from the collected data set are analyzed with Multiple Signal Classification (MUSIC) DOA estimator. Generally, the sparse array estimates agree with the full array.

Mikko notes that his next paper on applying deep neural nets to the problem of near-field localization will be presented at this years VTC2021 conference, so we are looking forward to that paper too. 

21 element array connected to a 21-input phase coherent RTL-SDR array
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SATSAGEN Spectrum Analyzer Software Updated: Now Supports RTL-SDR

Back in March last year we first posted about the release of SATSAGEN, and program by Alberto (IU1KVL) that allowed the PlutoSDR to work as a spectrum analyzer. SATSAGEN has recently been updated to version 0.5, and it now supports the RTL-SDR, HackRF and Simple Spectrum Analyzer hardware as well. 

Spectrum analyzer software allows you to monitor spectrum activity over a bandwidth much larger than what your SDR supports. It works by rapidly sweeping over multiple frequencies and stitching the spectrum slices together.

Some highlights of the new features include:

  • Works with:
    • ADALM-PLUTO
    • HackRF One
    • RTL-SDR Dongles
    • Simple Spectrum Analyzer series like NWT4000, D6 JTGP-1033, Simple Spectrum Analyzer, and so on.
  • Video trigger, real-time trigger, and fast-cycle feature
  • ADALM-PLUTO custom gain table and Extended linearization table for all devices
  • Transmit from raw format files
  • I/Q balance panel
  • Waterfall
SATSAGEN Interface
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NanoVNA V2 Enclosure now Available on Amazon

Just a brief post to note that our third party NanoVNA V2 enclosure is now available for purchase on Amazon USA. The price is US$19.95. The enclosure is also still available on our own webstore with free worldwide shipping from China to most countries. We also note that that NanoVNA V2 is currently out of stock, but we expect the manufacturer to supply us near the end of February.

Includes 1x Plastic NanoVNA V2 Enclosure, 1x Carry Case 1x Battery Terminals (Optional to install), 1x Matte Anti-Glare Screen Protector, 4x Enclosure Screws

This is a plastic enclosure and protective case for the NanoVNA V2 and V2+. Protect your NanoVNA V2 with a rugged plastic enclosure and carry case. The case case can be used to store the calibration kit as well. A standard 18650 battery (flat top non-protected) can be installed via the battery terminals if desired. Requires assembly - please consult the installation instructions PDF.

Please note does NOT include NanoVNA V2, NanoVNA calibration kit or battery. These are displayed in the photos for demonstration purposes only. 
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Installing and using RTL-SDR and GQRX on a PinePhone

Over on YouTube channel "Privacy & Tech Tips" has uploaded a video demonstrating how it's possible to run GQRX with an RTL-SDR on a PinePhone. In the video the presenter shows how to set up the screen so that GQRX is fully visible, demonstrates GQRX running, and then goes on to show exactly how to install the RTL-SDR drivers on the PinePhone.

The PinePhone is an open source smart phone that can run a full Linux distribution. A PinePhone sells for US$149.99 or $199.99 for a higher end version with more RAM and storage.

RTL-SDR On The Pinephone! Demo, Installation/Hardware

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Using 50 Lines of Python Code to Decode NOAA APT Weather Satellite Images

There are already many image decoders for the NOAA APT weather satellites available, with the most common and feature rich program being the abandoned freeware "WXtoIMG".

However many people may not know how simple the APT digital signal processing code is. Over on his blog post Dmitrii Eliuseev explains how only 50 lines of Python code are required to decode an image from received APT audio. Dmitrii's post shows how a Hilbert transform is used on the APT audio which is essentially the entire decoding step. This is then followed by a for loop that calculates the pixel luminosity from the decoded data, and plots it onto an image file. 

Of course the image is only grayscale (or in Dmitrii's case he decided to use greenscale), but adding false color and various other image enhancements found in advanced software like WXtoIMG are just standard image processing techniques.

Dmitrii concludes with the following:

Interesting to mention, that there are not so many operational radio communication systems in the world, the signal of which can be decoded using 20 lines of code. The NOAA satellites are about 20 years old, and when they finally will retire, the new ones will most likely be digital and format will be much more complex (the new Russian Meteor-M2 satellite is already transmitting digital data at 137 MHz). So those who want to try something simple to decode can be advised to hurry up.

[Also mentioned on Hackaday]

Simple decoding of NOAA APT satellites in Python
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DragonOS: BladeRF-wiphy Demonstration

Recently we posted about bladeRF-wiphy which is open source code that can turn a bladeRF software defined radio into a software defined WiFi access point. The bladeRF 2.0 is a relatively low cost SDR which costs $420 for the low end version. It is capable of both transmit and receive (2x2 MIMO) with a 47 MHz to 6 GHz frequency range and 61.44 MHz sampling rate.

Over on YouTube Aaron who created DragonOS has uploaded a video demonstrating bladeRF-wiphy in action. He writes:

This video demonstrates Nuand’s new open source 802.11 modem/FPGA available for the bladeRFxA9. Everything will be Pre included in DragonOS Focal to setup an open AP and hopefully whatever’s required for use within Kismet.

Minor configuration is needed for the open AP, while Kismet integration should be pretty straight forward.

This is an awesome addition to the bladeRF and I look forward to seeing what else is possible with this new open source 802.11 compatible modem!

DragonOS Focal BladeRF-wiphy w/ Open Wi-Fi AP and Splash page (bladeRFxA9)

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bladeRF-wiphy: Open Source WiFi Access Point on a BladeRF

Back in August 2020 we posted about OpenWiFi , an open source implementation of the full IEEE802.11/Wi-Fi stack for FPGA and SDR combo board. Recently the team at Nuand have released their own WiFi implementation called "bladeRF-wiphy" for their bladeRF 2.0 software defined radio. The code is implemented in VHDL, which runs directly on the bladeRF's on board micro xA9 FPGA.

The bladeRF-wiphy project is an open-source IEEE 802.11 compatible software defined radio VHDL modem. The modem is able to modulate and demodulate 802.11 packets (the protocol WiFi is based on), and run directly on the bladeRF 2.0 micro xA9’s FPGA.

The bladeRF-wiphy coupled with Linux mac80211 allows the bladeRF 2.0 micro xA9 to become a software defined radio 802.11 access point! 802.11 packets (PDUs) are modulated and demodulated directly on the FPGA, so only 802.11 packets are transferred between the FPGA and libbladeRF.

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