Category: RTL-SDR

FAASGS: A Setup to Build a Fully Automatic Amateur and APT Weather Satellite Ground Station

Over on GitHub stdevPavelmc has released his software called FAASGS (Fully Automatic Amateur Satellite Ground Station). FAASGS is an open source program that allows RTL-SDR users to set up a satellite ground station that tunes, record and generate images for NOAA APT weather satellites, as well as records FM amateur radio satellites. The software runs on a single board computer such as a Raspberry Pi, however in the authors own setup he uses an Orange Pi Prime board. The features include:

  • Web interface to see the next passes, the recorded ones, and details for it.
  • Receive any satellite in FM mode (SSB is possible but no there is doppler control yet, so no SSB by now)
  • Record the satellite pass and keep the audio for later.
    • APT WX audio is preserved in wav format and 22050 hz of sampling (the format wximage needs to work with)
    • FM audio satellites is preserved in .mp3 mode but with high quality settings, and other tricks.
      • The spectrogram of the audio is embedded as album art (see below).
      • The pass data and receiving station are stored in the mp3 tags.
  • Automatic decode APT images from WX sats (NOAA 15, 18 and 19)
  • For the voice FM sats we craft a spectrogram and embedd the metadata of the pass on the image
FAASGS main screen showing recordings
FAASGS screen showing an FM amateur radio satellite pass

DragonOS: Decoding FT8 on Linux with WSJT-X

DragonOS is a ready to use Ubuntu Linux image that comes preinstalled with multiple SDR program. The creator of DragonOS, Aaron, uploads various YouTube tutorials showing how to use some of the preinstalled software. This month one of his tutorials covers how to use a SDRplay RSP1A or a HackRF to receive and decode FT8 with the preinstalled software WSJT-X or JS8Call. Aaron also notes that an RTL-SDR could also be used as the SDR.

In the video he covers how to set up a virtual audio cable sink in Linux for getting audio from GQRX into WSJT-X, setting up rigctld to allow WSJT-X to control GQRX, configuring GQRX, CubicSDR and WSJT-X, and finally downloading and using GridTracker.

DragonOS Focal Receive FT8 w/ WSJT-X (RSP1A, HackRF One, GQRX, CubicSDR, GridTracker)

SignalsEverywhere: Installing and Configuring OP25 Phase 1 & 2 Digital Voice Decoder on Linux

In this weeks video Sarah from the SignalsEverywhere YouTube channel show us how to install and configure the OP25 software on a Linux machine. OP25 is a Linux based P25 digital voice decoder which works with RTL-SDR dongles. It is capable of decoding both Phase 1 and Phase 2 systems. Installation is fairly simple via an installation script, but it does take some time to install. After installation Sarah shows how to configure the software in order to properly follow a trunked P25 system. In order to help with importing talkgroup information from a premium RadioReference account Sarah has also created an automatic importer Python script which is very useful.

OP25 Installation and Configuration Tutorial | Setup OP25 P25 Phase 1 and 2 SDR Decoder on Linux Pi

GNU Radio 3.9.0.0 Released

GNU Radio is an open source digital signal processing (DSP) toolkit which is often used in cutting edge radio applications and research to implement decoders, demodulators and various SDR algorithms. Version 3.9.0.0 has recently been released. Below is part of the release text, but please see the official release post for the full list of changes. 

The future is not set, there is no fate but what we make for ourselves. In this very spirit, GNU Radio 3.9 packs a whole bunch of power when it comes to transforming the way GNU Radio and its ecosytem can be developed in the future.

You’ll find the release tags and signed tarballs now on github, and later on gnuradio.org/releases/gnuradio.

Not only did we have great progressions from old dependencies that proved to be all too problematic (SWIG, Python2), but also did we see an incredibly influx of people actively working on how maintainable this code base is. This will nurture the project for years to come.

All in all, the main breaking change for pure GRC users will consist in a few changed blocks – an incredible feat, considering the amount of shift under the hood.

Hacking a Ceiling Fan Radio Control Signal with an RTL-SDR

Over on YouTube "River's Educational Channel" has uploaded a video showing how he was able to reverse engineer the wireless control signal from his ceiling fan remote, and use that information to create a new transmitter controlled via his smart home's Raspberry Pi.

In the video River uses an RTL-SDR and the Spektrum software to initially identify the remotes frequency, before moving on to record the signal in Universal Radio Hacker (URH). He then goes on to reverse engineer the signal and determine the binary control string for each button on the ceiling fan's remote control.

In part 2 which is yet to be released River will show how to transmit this signal via his Raspberry Pi 3B in order to integrate it with his smart home.

Hacking My Ceiling Fan Radio Signal With a $15 USB TV Tuner (RTL2832U)

FengYun-2G Confirmed to be Receivable with a WiFi Grid Dish

Back in November 2020 we posted about the release of a decoder for the FengYun line of geostationary weather satellites which provide full disk images of the Earth and are positioned to cover parts of Europe, Africa, the Middle East, Asia, Russia, and Australia. Back then only a few people had attempted decoding this, and it was believed that a 120cm satellite dish or larger would be required.

However, today on Reddit user u/Harrison_Clark55 has shown that it is possible to receive FengYun-2G with a typical 90-100cm WiFi grid dish. These WiFi grid dish's have proven to work well for other geostationary weather satellites such as GOES and GK-2A.

We do note that u/Harrison_Clark55's image appears to be missing a few lines of data, and they are based in Australia where the elevation of FY-2G could be quite high depending on what side of the continent they are on. So it's possible that receivers in lower elevations may still require a larger dish size to work.

Full Disk FY-2G image received by u/Harrison_Clark55 (see the Reddit post for full resolution image)

SATRAN: An Affordable Motorized Satellite Antenna Rotator

Recently we came across the SATRAN project by Daniel Nikolajsen, which is an attempt to design, build and sell low cost kits of an automatic motorized satellite antenna rotator for less than US$200. A motorized satellite antenna rotator is useful 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. This is also an idea used by the well known SATNOGS project which also provides a design for a 3D printed antenna rotator, and runs servers that archive received satellite data.

Compared to the SATNOGS design, the SATRAN design appears to be much simpler and easier to build. Although being a smaller unit it's only design to handle small compact antennas such as a 70cm Yagi. SATRAN is also controllable via a web interface and there is an Android App. The design is capable of rotating 360 degrees, and 110 degrees from zenith, which allows a user to cover the entire sky.

Daniel notes that SATRAN kits should be available for sale from Feburary/March 2021. He also notes that it is possible to 3D print most of the parts and to just purchase the electronics for a lower price.

More technical information about the project is available on it's Hackaday.io blog.

SATRAN 3D render and actual prototype

Using SDR to Investigate Telemetry Still Broadcasting from 1960’s Satellite Transit-5B5

Thank you to Derek @ok9sgc for pointing us to some work Reddit user u/Xerbot has been doing on receiving telemetry coming down from a "dead" 1960's satellite called Transit-5B5. The fleet of Transit satellites was used for military navigation with the first launch in 1959 and the last in 1988. All in the fleet have since died apart from Transit-5B5 which continues to transmit telemetry at 137 MHz when receiving power from in the sun. Derek writes:

Turns out that the TRANSIT 5B-5 satellite's telemetry still has signs of some of the satellite's systems operating (albeit with a questionable reliability). The satellite represents an amazing legacy for all the people that worked on it in the 1950s and 60s, but due to its age it is also very difficult to find technical documentation about the telemetry (or I should rather say impossible), so to make sense of the data that's being broadcast by the satellite would require many people receiving, decoding, and comparing their results, mainly to identify any patterns in the satellite's behavior and the resulting demodulated data.

Derek and u/Xerbot are asking the SDR community to help collect more sample data, which might help in finding a way to decode some of the telemetry. If you have data to contribute, you can contact @ok9sgc on Twitter, and u/Xerbot on Reddit.

This reminds us of an old post from reader happysat where he demonstrated with an RTL-SDR that many "dead" satellites are actually still transmitting telemetry. Due to suspected chemical breakdown of the onboard batteries, the satellites tend to turn themselves on again when the solar panels receive sunlight.

The Transit-5B5 Satellite Telemetry Signal at 137 MHz