Tagged: rtl2832u

Characterizing Yagi Antenna Directionality via ADS-B Reception

Over on his blog Alex Krotz has been investigating whether adding more passive director elements actually affects the directionality of his home made Yagi-Uda antenna. Instead of using modelling software, Alex wanted a more accurate result that took into account all the imperfections of his antenna.

His idea was to receive ADS-B signals with his Yagi and a dipole antenna, then compare the data received in order to determine in which directions the Yagi receives better than the dipole. To do this he first creates a standard 2D map of plane tracks collected over a 24hr period for both the dipole and Yagi. A gaussian blur is applied to the two maps in order to fill in blank space and the data is normalized. Then he simply subtracts the dipole plot from the Yagi-Uda plot. The resulting difference plot reveals a mapping of where the Yagi receives better or worse compared to the dipole in a 2D plane.

Directivity of the Yagi revealed by comparing against a dipole
Directivity of the Yagi revealed by comparing against a dipole

Hak5: Turning a Key Croc into an RTL-SDR Server

The Hak5 Key Croc is a pentesting tool designed for emulating USB devices such as keyboards. It is commonly used by pentesters for keylogging and keystroke injection. It has some advanced features like keyword detection which can be used to detect when a certain word is typed. Under the hood it runs Linux on a quad-core ARM processor.

Over on the Hak5 YouTube channel Glytch shows us that he's been using the Key Croc as a remote RTL-SDR server. The server is setup through a payload script, which is then activated by typing "setup" into notepad on a PC. The keystroke logging and keyword detection feature detects the setup keyword, and runs the payload script which installs the RTL-SDR drivers and rtl_tcp server all while using the keystroke injection feature to output the install progress. Then it is a simple matter of plugging in an RTL-SDR, and connecting to the rtl_tcp server on a program like SDR#. 

Glytch notes that this is useful because you can run the entire Key Croc server and RTL-SDR on a portable battery pack, and now you have a remote SDR that you can place anywhere within your WiFi network.

Turning a KeyCroc into an RTL SDR Server w/ Glytch

DragonOS: Decoding Iridium Satellites with the Iridium Toolkit and an RTL-SDR

DragonOS is a ready to use Linux OS image that includes various SDR programs preinstalled and ready to use. The creator Aaron also runs a YouTube channel that has multiple tutorial videos demonstrating software built into DragonOS.

In his latest video Aaron explores Iridium reception with an RTL-SDR Blog V3, RTL-SDR Blog Active L-Band Patch Antenna and Iridium Toolkit/gr-iridium. Iridium is a satellite constellation that provides services such as global paging, satellite phones, tracking and fleet management services, as well as services for emergency, aircraft, maritime and covert operations too.

In the video he shows how to edit the config file to turn the bias tee on, how to record Iridium data, how to install the AMBE voice decoder, and finally how to decode the Iridum data with Iridium toolkit and play voice recordings.

DragonOS LTS Decoding Iridium satellites with the Iridium toolkit (gr-iridium, RTL-SDR)

DSD (Open Source) with dPMR Decoding and Windows Binaries Released

Digital Speech Decoder (DSD) is an open source program for decoding signals containing digital speech, such as DMR and P25. The open source version has been mostly surpassed in use over the last few years by the closed source DSD+ version. However, work is still ongoing on the open source version, and a recent fork by Louis-Erig HERVE @LouisErigHerve has added support for Digital Private Mobile Radio (dPMR) decoding.

dPMR is an open, non-proprietary trunked radio standard that supports both data and digital voice transmission. A licence free variation for short range communications called dPMR466 uses the 446.1–446.2 MHz band. Other modes allow for efficient peer to peer to peer operation (mode 1), operation with a base station repeater (mode 2), or with a trunking signal (mode 3).  All dPMR signals operate in FDMA mode with an efficient bandwidth of only 6.25 kHz. dPMR is also known as Icom IDAS and Kenwood NEXEDGE.

Code for Louis-Erig's DSD fork can be found on his GitHub, and he has also released binaries for Windows on his website. Over on his Twitter he has also been mentioning that he has been able to get around the basic privacy modes on DMR.

dPMR radios, data stations and repeater hardware.
dPMR radios, data stations and repeater hardware.

Tech Minds: Testing the OpenEar DMR TETRA ADSB POCSAG Decoder for RTL-SDR

Back in March we posted about the release of OpenEar, a standalone TETRA decoder for the RTL-SDR. Since then OpenEar has undergone massive developments, not only improving upon the TETRA decoder, but adding DMR, ADS-B and POCSAG decoders as well as a waterfall display.

Recently Tech Minds reviewed this software on his YouTube channel. In the video he shows how to download the software, install the rtlsdr.dll file, and run and use the software. He then demonstrates reception of an amateur radio DMR repeater, reception of POCSAG pager messages and finally reception of ADS-B aircraft messages.

OpenEar Digital Decoder - DMR TETRA P25 ADSB POCSAG RTL-SDR

Building a Remote SSB Receiver with an RTL-SDR, OrangePi and GNU Radio

Over on his blog F1ATB has uploaded a post explaining how he created an RTL-SDR or HackRF based remote SSB receiver controllable with an internet browser. To set this up he uses an Orange Pi One Plus single board computer which runs several GNU Radio based digital signal processing flow graphs. Then a Python server serves a custom HTML and Javascript based web interface with waterfall that can be controlled remotely over the internet. In the post he explains the GNU Radio DSP flowgraphs that he's built, and notes that he will explain the HTML and Javascript side in another future article.

The SSB receiver block diagram
The SSB receiver block diagram

A Talk on 21cm Hydrogen Line Amateur Radio Astronomy

The Amateur Radio Experimenters Group (AREG) recently held an online talk with guest speakers Phil Lock and Bill Cowley, talking about amateur radio astronomy. In the talk they note how they use an RTL-SDR as their radio.

Cheaper electronics has created great possibilities for Amateur Radio Astronomy. This talk will describe a local project to receive and map the distribution of 1420 MHz signals from neutral hydrogen in our galaxy. We briefly describe the history of 21cm RA and why it’s still of great interest to astronomers. We outline some challenges over the last few years in assembling a 2m dish with custom feed, electronics and signal processing, then show recent results from our project.

The image in the thumbnail shows recent signals (May 17th) recorded over a 24 hour period for dish elevation of 53 degrees. The signal changes as the antenna points to different parts of the Milky Way.

https://www.areg.org.au

The World of Amateur Radio Astronomy - Listening to the Galaxy

Open Weather: An Artistic Performance Involving Live NOAA APT Signal Decoding for Sound Arts Festival

Just after our post a few days ago about an art project involving weather satellite reception with SDRs, we received a story submission about an artistic performance with similar weather satellite and SDR themes. The submission from Sasha Engelmann reads:

Open Work, Second Body is a live-streamed performance by designer Sophie Dyer (@sophiecdyer) [M6NYX] and geographer Sasha Engelmann (@sashacakes) [M6IOR] in collaboration with the author Daisy Hildyard. The work was performed twice during Reveil 2020, a global sound arts festival streaming sounds from listening points around the planet on the day of the International Dawn Chorus.

Open Work, Second Body asks: From the climate crisis to coronavirus: what are the tools we need to make sense of events unfolding on vastly disparate scales? Through spoken word, field recordings and live radio reception of two NOAA satellite images, the work probes the porous boundaries between our bodies, local atmospheres and weather systems.

Still image capture from livestream of Open Work, Second Body, AM performance, May 2nd 2020

Due to lockdown constraints in London, Sophie and Sasha were not able to be in the same place or to leave their apartments, so they performed the work via simultaneous streams from their respective balconies in South East and North West London. Using RTL-SDRs, Turnstile antennas, Open Broadcast Software and collaborating with two NOAA satellite passes, Sophie and Sasha shared the process of decoding NOAA satellite images with hundreds of viewers around the world, employing spoken word poetry and field recordings to complicate relationships of local and global, weather and climate, the individual and the collective. 

Recordings of the performances can be found at the links below. 

☀️Morning: https://youtu.be/-5JrxwNpJqI [performance starts at 05:25]
?️ Afternoon: https://youtu.be/h88zaCtX8cw [performance starts at 05:00]

Still image capture from livestream of Open Work, Second Body, PM performance, May 2nd 2020
Still image capture from livestream of Open Work, Second Body, PM performance, May 2nd 2020

Open Work, Second Body is part of Sophie and Sasha's larger artistic research and design project Open Weather, which employs ham radio, open data and feminist theories and approaches to build new and diverse communities around satellite image decoding and weather sensing. The Open Weather web platform will be launched in Summer 2020 and will host an archive of SDR-generated weather images, visually rich how-to guides for those with no radio and engineering experience, and material about Sophie and Sasha's collaborative artistic practice. 

For Open Work, Second Body, Sophie and Sasha would like to thank the Soundcamp Team: Grant Smith, Dawn Scarfe, Christine Bramwell, Maria Papadomanolaki and Ciara Drew. They are grateful to Daisy Hildyard for her willingness to be in conversation with them, Bill Liles NQ6Zfor technical advice, Jol Thoms for sound design, Rachel Dedman, Laure Selys and Arjuna Neuman (Radio Earth Hold) for early curatorial input, Akademie Schloss Solitude for the support of a residency, the satellites NOAA 18 and NOAA 19 and the RTL-SDR and wider ham radio community. 

http://www.sophiedyer.net

http://www.sashaengelmann.com

It's very cool to see technical hobbies like ours starting to make an impact in art and reaching a wider audience. More content and images available on Sophie's Open Weather webpage, and Sasha's Open Weather webpage. 
Open Weather Live Stream