Category: Applications

IEEE Spectrum: Chasing Weather Balloons with Software Defined Radio

Electrical engineering magazine IEEE Spectrum has recently shared a story about how RTL-SDRs can be used for chasing weather balloons. With an RTL-SDR, antenna and appropriate decoding software, it is possible to decode the telemetry signal from weather balloons radiosondes, and track their live GPS location.

The author, James Provost explains how chasing and hunting weather balloons can be a fun sport. To help with his hunt James uses an RTL-SDR, a directional antenna and the Sondehub Tracker website.

First James logged onto Sondehub Tracker which aggregates multiple weather balloon signals received by volunteer ground stations. One feature of Sondehub is that it can predict an approximate landing position of a balloon. It however cannot track a balloon right to its final landing spot as usually the ground station will loose signal when the balloon gets too low.

Knowing the approximate landing position, James drove out to the indicated location and then took out his RTL-SDR and directional antenna and was able to track and find the radiosonde by decoding the telemetry signal with Sonde Monitor

IEEE Spectrum Weather Balloon hunting graphic

Running KrakenSDR on the Steam Deck

DragonOS creator Aaron has recently put out a few Tweets showing that he has been successful at getting his KrakenSDR to run on a Steam Deck. The Steam Deck is a handheld gaming device made by Valve, the creators of several famous PC games and the Steam game store. It is essentially a powerful handheld computer with screen and good battery life, so it makes an excellent mobile SDR computing platform too.

Aaron notes that the output power of the Steam Desk isn't enough to power the KrakenSDR itself, but after adding an external battery pack it works well.

Frugal Radio KrakenSDR Part 1 – Unboxing, Antennas and Initial Setup

Over on the Frugal Radio YouTube channel Rob has uploaded part one of his two part series on the KrakenSDR. The KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding and passive radar. We successfully crowd funded the device on Crowd Supply.  

In the video Rob unboxes his KrakenSDR, and explains how he will use it for radio direction finding. He shows his setup including the other required parts, like the Pi 4, and power supply, and then goes on to show the software installation process which involves burning an SD card and downloading an Android app. Next he sets up his antenna array by printing the antenna spacer and using the Excel antenna array calculator sheet.

Rob notes that Part 2 is coming in one to two weeks and will show him using the KrakenSDR in his vehicle to locate the source of a transmission.

KrakenSDR Unboxing / Prep & Setup device & antennas : Part 1

SATRAN MK3 Antenna Rotator Hardware Kit Released

Back in January 2021 we posted about the release of the SATRAN product, which is a low cost automatic motorized satellite antenna rotator kit. The rotator is deigned to be used for pointing high gain directional antennas such as a Yagi or satellite dish at low earth orbit satellites which can move across the sky quickly. They also supply an Android App for easily controlling the rotator.

Recently SATRAN MK3 (version 3) has been released a few days ago and costs € 175,00 for the kit, but does not include the plastic parts which need to be 3D printed. Unfortunately the kit appears to already be sold out, but we suspect they are working on getting more kits soon. Also of note is that they are based in Sweden and cannot ship to the US or Canada.

The email announcement reads:

"There's a new Satran in town!"

I'm glad to announce the newest Satran MK3 Rotator which is now available in the shop. The former cast aluminum version has been abandoned since the production was way too time-consuming and expensive.

The new MK3 has taken all the advantages of both older versions and returned to a more open source and 3D-printable design. This cuts the price by two thirds, while still getting a really user-friendly, compact and able device.

...and there's a new app!

Some users have reported issues with their Android app crashing, so today a new version of the app (2.3) has been finished and will be available in a day or two. If you don't get an update notification automatically in your app, visit Google Play to check for the latest version. 

The app also have a more extensive list of satellites and the possibility to search for a satellite by its Norad ID. 

SATRAN MK3 Antenna Rotator
SATRAN MK3 plastic parts that need to be 3D printed.

KrakenSDR now Shipped to the Majority of Crowd Supply Backers

If you weren't aware of it, KrakenSDR is our RTL-SDR spinoff project and is a 5-channel coherent RTL-SDR that we have successfully crowdfunded for over on Crowd Supply. KrakenSDR is the successor to our previous 4-channel coherent product called the KerberosSDR. With a radio like KrakenSDR that is capable of coherence between channels, interesting applications like direction finding and passive radar become possible. You can also use it as five independent RTL-SDRs should you chose to.

We wanted to note that all units preordered through the Crowd Supply crowd funding campaign are now at the Crowd Supply / Mouser warehouse, and the majority have already been shipped out to customers!

The KrakenSDR with 5x Krakentenna's
The KrakenSDR with 5x Krakentenna's for Radio Direction Finding

Additional units for new purchasers are in a mixture of production and freighting and will be available for fulfillment as soon as we can. We are constrained by supply and production time, so if you're interested in a KrakenSDR, please get your order in so that you have an earlier place in the queue.

KrakenSDR Production
KrakenSDR Boxes

Other Recent KrakenSDR Updates

Wiki Manual: Our Wiki manual and guide is up at It covers topics from what you need to get started, radio direction finding theory and background, antenna array setup, KrakenSDR Web-GUI software guide, Android App guide and a Passive Radar guide. 

GNU Radio: We have recently released a beta version of a KrakenSDR GNU Radio block and examples at

GNU Radio KrakenSDR DOA Flowgraph

Install Scripts, VirtualBox Images, Docker: For general vehicle based direction finding, which is the most popular application, we recommend using our premade Raspberry Pi 4 image for easy almost plug and play setup. But to ease installation on other computing devices (especially as the Pi 4 stock is non-existent at the moment due to the supply chain crisis) we've now created an automatic Linux install script and a Virtual Box image which can be run on Windows or Linux host machines. Third parties have also released a Docker container. See this page on our Wiki for more information.

Customer Feedback: We've also had some great customer feedback so far with one user submitting examples of his success in locating transmitters like a 162 MHz NOAA weather station, and various fox hunt beacons. 

KrakenSDR Direction Finding with Android App

Arrow Antennas: For fixed site direction finding installs, Arrow Antennas is now shipping their 5-element dipole antenna array.

If you're interested in the latest KrakenSDR updates, please follow us on the Crowd Supply mailing list, and keep an eye out for our official website releasing soon.

Tracking and Decoding Guide for NOAA Weather Satellites

Thank you to Samual Yanz (N7FNV) for submitting a guide that he's created about tracking and decoding NOAA weather satellites. The guide can be downloaded from this link as a PDF

Currently there are three operational polar orbiting NOAA weather satellites that transmit image data in the APT format at 137 MHz. When one of these satellites pass overhead, it is possible to use an RTL-SDR with appropriate satellite antenna and software to receive the satellite weather images they transmit.

Samual's guide focuses on the software and shows how to setup Virtual Audio Cable for piping audio between programs, SDR# for receiving the signal, Orbitron for tracking the satellite and WXtoIMG for decoding the image.

SDR#, Orbitron and WXtoIMG

Using RTL-SDR to Detect Weak Vibrations in Nanomechanical Resonators Based on Graphene Drums

Thank you to Joel Moser who has submitted news about his teams scientific research work at Soochow University in Suzhou, near Shanghai, China which makes use of RTL-SDR Blog V3 dongles in their research to replace bulky and expensive analysis equipment such as a lock-in amplifier, a vector network analyzer, or a spectrum analyzer. Their results show that an RTL-SDR can produce results as good as those more traditional pieces of equipment. 

The researchers have also provided a summary video, which helps explain the science in an easier way. In a nutshell, as far as we understand it, they first use a laser optical interferometer to measure the graphene nanomechanical resonator, and then connect the output of the interferometer to the RTL-SDR, where the signal can be measured on a PC, and then easily put forward to further DSP processing in GNU Radio.

One interesting result is that they were able to recover very clear audio from the graphene nanomechanical resonator using the RTL-SDRs. This is highlighted in the video from around 4:25. Also provided via their website are two audio files demonstrating a clear reading of a Shakespeare sonnet, and a musical.

Our project is about detecting weak vibrations in nanomechanical resonators based on graphene drums. Graphene is an atomically thin membrane of carbon atoms. Graphene drums are made by suspending the membrane over an array of cavities nanofabricated in silicon oxide. Vibrations of the membrane are driven using a capacitive force at frequencies ranging from 10 to several hundreds of MHz. The detection of vibrations is done by optical interferometry, with the electrical output of our photodetector connected to a radio frequency measuring instrument. Usually, the measuring instrument is a lock-in amplifier, a vector network analyzer, or a spectrum analyzer, which are all rather bulky and expensive systems.
In our work, we demonstrate that graphene nanomechanical vibrations can be adequately measured with RTL-SDR v3 dongles. We find that the quality of our dongle-based measurements is as good as that of measurements made with a low noise spectrum analyzer, provided the driving force is not too small. 
We take full advantage of your dongles by measuring the amplitude of two vibrational modes in parallel. For this, we split the output of the photodetector and connect it to two dongles. Measuring multiple modes in parallel is very valuable for nanomechanical sensing applications, as more information can be extracted compared to single mode measurements. However, this is a challenging task that requires several instruments collecting data in parallel. Here, we demonstrate that a composite of SDR dongles offers an alternative that is remarkably simple and inexpensive per frequency channel.
Finally, we show that our software-based instrument can be employed to demodulate human voice encoded in nanomechanical vibrations. For this, we drive vibrations with a frequency modulated force. As a baseband signal, we alternatively use a Chinese song performed by one of us, poetry by Shakespeare, and an excerpt from a musical.
We are now improving our measurement setup by synchronizing the clocks of several RTL-SDR v3 dongles to measure vibrational modes coherently. We are also greatly interested in employing your KrakenSDR for even better and cleaner multimode nanomechanical measurements. 
A recent paper about our work can be freely accessed here:
Audio files for our demodulated nanomechanical signals can be found at the same address, but they are buried in a supplemental material (media) folder. Alternatively, the paper and the audio files can be found here:
Our work is very much inspired by recent scientific projects based on your dongles, many of which are cited in our paper.
Resonator and measurement setup.

Open-Weather: A Browser Based NOAA APT Satellite Image Decoder

Thank you to Sasha Engelmann for letting us know about the release of the Open-Weather community's web browser based NOAA APT decoder. The decoder allows for easy NOAA satellite decoding by allowing you to upload a wav file recording of a NOAA satellite pass, and it will decode it into an image within the browser. 

The project emerged from a desire to understand the process of decoding APT audio recordings into NOAA satellite images, and a need for an accessible browser-based decoder for new practitioners during open-weather DIY Satellite Ground Station workshops.

While we were inspired by Thatcher's APT 3000, we felt accessibility, documentation and features could be expanded and improved. open-weather apt allows you to select an audio file on your computer, choose a demodulation method, add histogram equalisation and download images. The website does not store your personal data, including your location or any files you upload.

Documentation of the decoder is available on Public Lab here:

open-weather apt is forked from Thatcher's APT 3000. It is a collaboration between open-weather, Bill Liles NQ6Z and Grayson Earle.
Open-weather web based APT decoder