July 19, 2023

Fox Hunting with the KrakenSDR

Over on his YouTube channel Mark Jessop has uploaded some dash cam footage showing him using a KrakenSDR and a custom LED display to hunt down three amateur radio transmitters during a fox-hunt.

An amateur radio fox-hunt is an activity where someone will hide a transmitter within a defined area, and it is up to the hunters to use radio direction finding equipment to find it. The KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding.

Mark uses a custom four element array on the roof of his car, which is connected to his KrakenSDR. Instead of the KrakenSDR app, Mark prefers to use his custom LED HUD to displays the bearings and signal power directly.

Some annotated and sped-up dash-cam footage captured during the July 2023 Amateur Radio Experimenters Group Fox-hunt. We run these monthly, and usually have three transmitters hidden around the Adelaide (South Australia) area.

I run a KrakenSDR with a custom-built 4-element antenna array mounted to the roof of my car. This gives me direction estimates to the target transmitter, at least when the signals are strong enough!

I've also build a heads-up-display which helps me safely make use of the KrakenSDR's output data while driving. The source code for this is here: https://github.com/darksidelemm/neopixel-doa-display

The display is shielded so it's not visible from outside the car - Red & Blue lights on your dashboard can give the wrong impression!

AREG Fox-hunt - 14th July 2023

Watch this video on YouTube

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July 17, 2023

Goestools Now Ported to Run on Windows

Thank you to Carl Reinemann (aka USRadioGuy) for letting us know through his blog post that goestools has recently been ported to Windows. Goestools is a software package that is used to receive and decode images from GOES weather satellites. In the past it was only available for Linux systems, however recently thanks to the work of Jamie Vital, goestools has now been ported and can run on Windows. Carl Reinemann has confirmed that the software runs perfectly on Windows. Our GOES tutorial should also be easily modified to work with the Windows port.

The Windows port can be downloaded from goestools-win on GitHub. If you are interested, Jamie Vital is also the author of Vitality GOES, which is a program that can display the received weather images in a nice GUI.

Alternatively we note that another cross platform GOES decoder is SatDump which is currently the most popular choice for GOES.

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July 13, 2023

Building a DIY Portable 137 MHz Yagi Antenna for LRPT

Over on his YouTube channel dereksgc has uploaded the next video in his series on satellite reception. In this video he shows how to build a Yagi antenna tuned for 137 MHz, which is great for receiving NOAA APT and Meteor M2-3 LRPT. Note that a Yagi antenna will give you stronger reception compared to a turnstile, QFH or V-Dipole, but as it is a directional antenna you will need to manually point it towards the satellite as it passes over your location.

For Meteor M2-3 LRPT, a Yagi antenna may be beneficial, as it appears this satellite is having some issues with signal strength, due to a possibly defective antenna that did not fully unfold on the satellite.

The Yagi antenna design is a four element design, with one reflector, two directors and one driven dipole element. The physical construction consists of a piece of wood for the boom, brass welding rods for the elements, and a terminal block for the active dipole element. 3D printed handles are added for easy holding and the RTL-SDR and LNA sit directly on top of the boom.

Watch this video on YouTube

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July 13, 2023

Hystérésia: An Art Installation that Listens to Zombie Satellites

Thank you to Stéfane Perraud, Aram Kebabdjian and team for submitting news that they have recently launched an art project in Lausanne, Switzerland called "Hystérésia". The installation is technical art, which consists of an autonomous satellite receiving station designed to receive beacons from old "zombie" satellites, and then broadcast their signals audibly. A description of the ground station can be seen here.

Zombie or Dead satellites are satellites that are officially decommissioned and powered down, but have unintentionally reactivated. This often happens as over time the batteries on these satellites can undertake a chemical reaction from thousands of solar recharge cycles which eventually results in a short circuit. Hence the satellites reactivate when in sunlight. If you are interested we have an old post on this phenomena back from 2014.

The system is based on an antenna rotator with two Yagi's that tracks the zombie satellites as they pass over the sky. A QFH antenna has also been spotted in their images. Based on the waterfall images, an SDRplay RSP is used as the receiver, and some computing device is used to demodulate the signal into audio. Stefan adds:

Technically we are using a double yagi 137 and 145 plus a 777 antenna from diamond to catch 200 mHz

We developed a python based software that’s controlling a sdr software based on gnu radio.

We update TLE everyday, our azimuth and élévation rotor follow the satellites and we catch the signal with a sdr uno, plus a switch that choose antenna with the good satellite.

The machine is monitored by a bench of sensors , wind, humidity, temp. It can be control by internet via the website

The machine search for peaks around the chosen frequency,
Also the sound is processed by max/msp, we denoise it and we make music out of it

The 3 metallics pavillons blows the sound noise to the audience
Each time a satellite shows up, the machine sends a story told by one of our recording, a woman actors voice , it tells a specific history that’s tells a narrative about the satellite that’s on air … but in French

If you are unable to visit the installation in person, it appears that their website also broadcasts the last received satellite's sound. The website also shows photos of the history of the zombie satellites.

If you're interested in other art based on satellites and software defined radios, have a look at our previous post on the open weather project, and the "signs of life" project. Another SDR art project was 'Holypager', an art installation that continuously prints out pager messages received by a HackRF, and "ghosts in the air glow" project which used the HAARP antenna array to broadcast an art project.

Hysteresia montage (click for large version)

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July 12, 2023

RFNM Updates: Motherboard Prototypes Manufactured

Back in April we posted about the RFNM, an upcoming software defined radio project which 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 via an RFFC2071A mixer.

Recently they've updated their blog and show that they have successfully manufactured the first prototype of the RFNM motherboard. The motherboard is the board containing the LA9310 RF and computing chips, and then they intend on having various daughterboards for tuners that will expand the tuning range and performance.

They also updated their pricing, noting that they have upgraded a few specifications. The motherboard is set to be priced at $299. It will be available for preorder in August, with an expected October delivery date.

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July 12, 2023

TechMinds: Detecting Bats with an Ultrasonic Sensor and Software Defined Radio

Back in 2018 we posted about someone who had combined an ultrasonic piezo speaker and an SDRPlay RSP1A in order to create a device that can detect the ultrasonic sonar sound from bats.

Recently on YouTube Matt from the TechMinds YouTube channel was able to create a similar system using a MEMS microphone from Knowles which can receive audio in the 100 Hz ~ 80 kHz range. He connects the microphone to a 3.3V supply and connects the output of the microphone to his SDRplay RSPDx.

The system was then able to successfully hear the sound of bat sonar at his home location in the UK.

Ultrasonic BAT Detector Using Software Defined Radio

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July 11, 2023

Receiving the STEREO-A Solar Orbiting Satellite with a 66cm Dish

STEREO-A is a satellite launched in 2006 which is orbiting the sun and used for making solar observations. Usually it is so far away that massive deep space satellite dish's are required to receive this satellite. However for the first time since it's launch, STEREO-A's orbit is taking it close enough to Earth for small home satellite ground stations to be able to receive the data and download some images of the sun.

Over on his Blog Scott Tilley has written up an article showing how it is now (temporarily) possible to receive and decode STEREO-A with a small 66cm dish. The satellite will be closest to Earth on August 17 2023, however Scott notes that since mid June the signal has already been dramatically increasing.

Scott's blog post explains the orbit, how the satellite transmits at 8.443.579 GHz, and shows his feed and hardware setup which involves a few filters, LNAs, GPS reference clock, a mixer and an Ettus B200 SDR. He also notes how he uses a modified motorized telescope mount to automatically track the satellite as it moves through space.

The rest of Scott's post explains how to use the "CCSDS Turbo R6 K8920" Decoder in SatDump to decode the signal and recover images, noting that some tuning of parameters was required and that because of the slow data rate it can take hours to get even one megabyte of data. He goes on to acknowledge everyone who figured out how to decode the image and telemetry data from the satellite, some observations on the STEREO-A beacon and finally some amazing images and animations he's received.

A weak signal from STEREO-A received back in mid June 2023

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July 8, 2023

SDRSharp 1915 Released: RTL-SDR Crashes Fixed

Thank you to SDR# author Youssef for updating SDR# (SDRSharp) and fixing a recent bug that was causing RTL-SDR units to crash whenever the frequency was changed. We are putting this post out to inform everyone who was having this issue to please update their SDRSharp version to 1915 which can be downloaded from airspy.com/download. Our guide at www.rtl-sdr.com/QSG can be used to walk you through the installation procedure for RTL-SDR dongles in SDR#.

The new update brings the RTL-SDR control menu down to the sidebar making it much easier to control the gain and sample rate settings. Other recent changes have also brought improvements to the RDS decoder which will be useful for DXers.

Please remember to show your appreciation to Airspy for allowing RTL-SDR users on their platform by checking out their range of higher end softwire defined radio products at airspy.com.

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