Category: RTL-SDR

NyanSat: A Low Cost Open Source Satellite Ground Station

Thank you to John D for writing in and letting us know that Wired magazine has recently run an article about the "Nyansat" project. Nyansat aims to bring low cost open source satellite ground stations to the masses. The goal is to democratize citizen access to space by allowing for easier collection of satellite data, or even for collaborative citizen science radio astronomy projects such as the detection of space debris or undocumented satellites. John writes:

While most people think of a satellite ground station as a giant dish mounted on top of a building in the desert, technically any radio receiver that tunes into a satellite's signal can be called a ground station.  Somewhere between the giant dish and the GPS chip in your phone is a ground station that uses a directional antenna to pull in the faint signals.  So unless you're only interested in geosynchronous satellites, the antenna needs to be aimed at the satellite, and that's where NyanSat comes in. 

The design of the NyanSat consists of a pan-tilt head, an Inertial Measurement Unit (IMU) for precise azimuth and elevation measurements, a motor-driver board, an optional OLED display, an optional GPS module, and is powered by an ESP32.  Full source code is available in their git repo, found at https://github.com/RedBalloonShenanigans/antenny. The NyanSat's software is written in micropython specifically for the ESP32, but obviously could be ported if desired.

Mounting an antenna, adding an RTL-SDR, and actually tuning in a satellite, is still up to the builder.

One of the goals of the NyanSat project is to eventually build up a network of ground stations that can collaborate to contribute frequently updated satellite ephemeris information.

When they're in stock, the project's sponsor, Red Balloon Security, has occasionally been offering a kit containing a custom PCB that is pre-populated with the ESP32 and motor driver; a pan-tilt gimbal; an IMU; and an RTL-SDR.  They've been selling them for $1.00(!), just to get them out in the hands of people.  Keep your eye open in case they get another batch in.

The Red Balloon store lists the kit as currently out of stock so we suggest keeping an eye on their store just in case any of the $1 kits come back in stock.

NyanSat will also present a live twitch demo at this years online DefCon conference on Friday Aug 7 6:30-8PM EDT and Sat Aug 8 6:30-8PM EDT. On Sun Aug 9 12:30 EDT they will hold another event where they judge the best work of the Nyansat community.

The SatNOGS project which we have covered many times before on this blog is quite similar with it's own open source antenna rotator design, however the Nyansat design looks a bit easier to build as it doesn't require 3D printed parts. Although critically from their demos we haven't seen what sort of sized antennas the gimbal chosen by Nyansat is capable of moving.

The NyanSat Pan/Tilt Gimbal Control Setup

Analyzing Lightning Discharges with an RTL-SDR and the Sage Network

Sage is a project working on creating geographically distributed sensor systems including cameras, microphones, weather and air quality stations in order to benefit the work of scientists. Recently on their GitHub they have uploaded a Jupyter Notebook showing how they have used an RTL-SDR V3 on a Linux Laptop to analyze lightning discharges. When lightning strikes, it creates a broadband RF pulse generally across the lower frequencies. This is how live lightning maps like Blitzortung work.

In their example Sage use a dipole antenna and analysis frequency of 30 MHz. The notebook doesn't offer much additional information, but provides Python Numpy and Scipy code which can be used to detect and plot the lightning pulses.

Graphing Lightning Pulses for the Sage Network

Frugal Radio: SDR Guide Ep 4 – Antenna Basics for SDR Beginners

In this episode of Frugal Radio's series of SDR beginners guide videos he discusses some antenna basics. He shows the most common types of antennas, provides several tips to help improve reception, and shows how to properly tune antennas using online calculators.

Near the end of the video he shows our multipurpose dipole antenna kit and shows how to adjust the telescopic elements for best reception. He demonstrates that simply extending the elements to the maximum length does not result in the best tuning, rather you need to tune the element length for the frequency being received to get the best results.

2020 SDR Guide Ep 4 : Antenna Basics for SDR Beginners inc RTL-SDR / Nooelec NESDR SMArt bundle

Frugal Radio: SDR Guide Ep 3 – Beginner Budget SDR Shootout

In this episode Frugal Radio explores the differences between three RTL-SDR dongles. In the video he compares a generic RTL-SDR, a Nooelec SMART and one of our RTL-SDR Blog V3 units. Initially the specifications are compared, and then he moves on to testing them on real signals with SDR#. Overall the RTL-SDR Blog V3 comes out with the highest final score thanks to it's additional features and low price.

2020 SDR Guide Ep 3 : Beginner Budget SDR Shootout (Generic vs Nooelec vs RTL-SDR v3) cheap SDRs!

SignalsEverywhere: SDRTrunk P25 Police Scanner Tutorial with two RTL-SDRs

Over on YouTube Sarah from SignalsEverywhere has uploaded a new tutorial video showing how to use two RTL-SDR dongles with the free SDRTrunk software to create a P25 Police scanner.

In the video she first shows how to install SDRTrunk in Windows and Linux, then how to install the JMBE codec required for decoding audio. She goes on to show how to import trunked system network data from a (paid) RadioReference subscription, how to blacklist unwanted talkgroups, and how to optimize operation with two RTL-SDR tuners. Finally she also shows how to set up the system manually if you don't have a RadioReference subscription.

SDRTrunk The FREE P25 Police Scanner! Windows and Linux Tutorial

Australian Teenager Exposes COVID-19 Patient Data via POCSAG Pager Network

A 15 year old Australian teenager has been accused of leaking sensitive COVID-19 patient data such as the phone numbers and addresses of people in quarantine, and conversations between health officials and doctors about COVID-19 patients. The leak occurred via a public web page that he had set up to share decoded POCSAG pager data that he received from his home.

Pagers are still typically used in many parts of the world by hospitals. It is a tried, tested and very reliable system for messaging, however most systems in the world send data out in unencrypted plain text for all to see. Anyone with a cheap scanner radio or $20 SDR and freely available software can decode every single message sent via paging from almost anywhere in a city as the signals are often extremely strong. Pagers are intended to be reserved for urgent infallible messaging, as paging is more reliable compared to mobile SMS since SMS messages do not always get through, or can be delayed by several minutes. Alternative secure communication channels such as SMS should be used for private information, however this protocol is not always followed due to the additional hassle.

The teen appears to have used either a Baofeng or RTL-SDR to receive the POCSAG pager signal available in his hometown in Western Australia. The pager signal was decoded with multimon-ng, and displayed via the PagerMon software. PagerMon creates a web page that displays pager messages in an easily readable format, and the page can be made accessible to the internet if desired. It seems that the teen is a scanner enthusiast, and did not intend to purposely leak patient data, however others found his PagerMon page and brought it to the attention of the media. His site has now been shut down, and officials have decided to shut down the pager system in favour of a double SMS system.

Some of the leaked messages via 9 News Perth
Some of the leaked pager messages via 9 News Perth

This is a story that repeats often all around the world. In the past we've seen whistleblowers report on patient data breaches in Vancouver, Kansas, and via an art installation in New York that continuously printed out pager messages.

Alpha Version of SDR++ Released

SDR++ is an open source general purpose cross platform SDR program that Alexandre Rouma (@WhatsTheGeekYT) has been working on for the past few months. Recently he released his first Windows Alpha version to the public which is available from the GitHub release page. The SDR++ GUI is inspired by SDR#, however, SDR++ as you might guess is programmed in C++ instead of C#.

In order to use SDR++ on Windows you will first need to have installed PothosSDR for the SoapySDR and volk support. To do this you can follow the instructions here. Thanks to the SoapySDR support it is able to run with most SDRs including the RTL-SDR.

To start the program, select your SDR from the source menu, change the sample rate (which is set to the minimum value by default), then click the play button. We tested it with both an RTL-SDR and HackRF, and both units worked just fine, although at lower sample rates the waterfall was a bit choppy. We do note that the software is very much in the alpha phase with only a few features implemented, and most menu items do not work yet. But the main features including WFM, FM, AM, SSB, CW demodulation as well as the spectrum and waterfall are all functional. Unfortunately there do seem to be a few stability issues as we experienced frequent crashes on our PC.

We'll be watching this software with interest to see how it progresses.

Current Features

  • Uses SoapySDR for wide hardware support
  • Hardware accelerated graphics (OpenGL + ImGui)
  • SIMD accelerated DSP (parts of the DSP are still missing)
  • Cross-platform
  • Full waterfall update when possible. Makes browsing signals easier and more pleasant

Coming soon

  • Multi-VFO
  • Plugins
  • Digital demodulators and decoders
  • Quick replay (replay last n seconds, cool if you missed a short signal)

Small things to add

  • Switchable bandwidth for demodulators
  • Switchable audio output device and sample rate
  • Recording
  • Light theme (I know you weirdos exist lol)
  • Waterfall color scheme editor
  • Switchable fft size
  • Bias-T enable/disable
  • other small customisation options
  • Save waterfall and demod settings between sessions
  • "Hide sidebar" option
  • Input filter bandwidth option

Known issues (please check before reporting)

  • Random crashes (yikes)
  • Gains aren't stepped
  • The default gains might contain a bogus value before being adjusted
  • Clicks in the audio
  • In some cases, it takes a long time to select a device (RTL-SDR in particular)
  • Min and Max buttons can get unachievable values (eg. min > max or min = max);
The SDR++ Interface
The SDR++ Interface

Frugal Radio: Using an Airspy and RTL-SDR To Scan the UHF Military Airband in SDR#

In Frugal Radio's latest video he explores how you can use an Airspy or RTL-SDR dongle to scan the entire military UHF airband spectrum in a few seconds via SDR#. Frugal Radio notes that there are often many signals in the UHF milair band, but they can be difficult to find without a scanner.

In the first video he compares his Uniden BCT15X hardware radio scanner against an Airpsy, noting that his Uniden takes 1:10 minutes to scan the entire band, whereas the Airspy running SDR# with the frequency scanner community plugin can scan the same bandwidth in less than 2.5 seconds. Faster scanning means that you are less likely to miss an active signal. In the second video he tries scanning with an RTL-SDR and notes that it can scan the band in 9 seconds.

How to use Frequency Scanner to Search UHF MilAir in 2.3 seconds in SDR# using AirSpy R2

$25 RTL-SDR v3 Military Air band search in under 10 seconds! Frequency Scanner SDR Sharp plugin test