Category: RTL-SDR

Vela Pulsar Glitch Detected with RTL-SDR Based Radio Telescope

On February 1st 2019 the HawkRAO amateur radio telescope detected a "glitch" during it's observations of the Vela Pulsar. A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish or directional antenna and a radio, like the RTL-SDR. The Vela pulsar is the strongest one in our sky, making it one of the easiest for amateur radio astronomers to receive.

Pulsars are known to have very accurate rotational periods which can be measured by the radio pulse period. However, every now and then some pulsars can "glitch", resulting in the rotational period suddenly increasing. Glitches can't be predicted, but Vela is one of the most commonly observed glitching pulsars.

The HawkRAO amateur radio telescope run by Steve Olney is based in NSW, Australia and consists of a 2 x 2 array of 42-element cross Yagi antennas. The antennas feed into three LNAs and then an RTL-SDR radio receiver. He has been observing the Vela pulsar for 20 months.

His observations indicate that Vela glitched and spun up by 2.5PPM at 14:09 UTC on Feb 1, 2019. He claims that this glitch detection is a first for amateur radio astronomy as far as he is aware.

If you're interested in Pulsar detection, check out a few of our previous posts on the topic.

The HawkRAO Amateur Radio Telescope Vela Glitch Detection
The HawkRAO Amateur Radio Telescope Vela Glitch Detection (Blue graph on the right indicates the glitch detection)

Decoding Es’Hail-2 DVB-S2 Realtime in Linux with LeanDVB

Last week we posted about M Khanfar's YouTube video that showed how to decode Es'Hail-2/QO-100 DVB-S2 on Ubuntu with the LeanDVB decoder. However, the method he showed was not in real time as it involved recording an IQ file in GQRX first, then decoding that IQ file. Similarly we also posted last week about a Windows based real time decoder.

M Khanfar recently wrote in again and wanted to show that real time decoding is possible with LeanDVB. The method is to simply pipe the output of the rtl_sdr command line decoder in LeanDVB, and then into VLC. He notes that his PC isn't actually fast enough to decode in real time without lag, but a modern i5 CPU would work well. The actual terminal command is shown in his YouTube video description.

This is Realtime live DVB-S2 Decoding done , without need to record .RAW file , its live and easy method by one click ! In this video i decoding 2MS symbol rate from wideband transponder of QO-100 beacon , you can decoding 1MS , 0.5MS , 333KS , 125KS symbol rate ! The lower Symbol, the faster speed for decoding! , the Amateurs operators on QO-100 Uplink DATV DVB-S2 at 0.5 , 333 , 125Ks , so its easy to Live Decoding Now ! With very low SNR ! , so the normal SDR can coverage wideband beacon of 2Ms symbol and all Ham uplink ! , if you have an SDR that can coverage 27.5 mb of bandwidth, so you can easy decoding Live a standard commercial satellite channels! But it need a high speed Pc .

QO-100 Realtime Live DVB-S2 Decoding

RSGB Talk – The Farnham WebSDR: DC to Microwaves on your Smartphone

Over on YouTube the Radio Society of Great Britain (RSGB) has uploaded a talk by Noel Matthews (G8GTZ) titled "The Farnham WebSDR: DC to Microwaves on your smartphone". The Farnham WebSDR runs 8 (soon to be 10) RTL-SDR dongles in order to cover multiple bands from DC to 2 GHz.

If you're interested in their talks, the RSGB also recently uploaded several other amateur radio related talks from their 2018 convention to their YouTube channel.

This presentation gives an overview of the Farnham WebSDR (http://farnham-sdr.com/) which currently covers the LF bands through to 10GHz. The presentation describes the system architecture and antennas currently used on each band and how the team has used RTL dongle receivers, available for under £10, to give good RF performance on all bands from DC to 10GHz. There is a demonstration of the SDR in use on both PC and smartphone.

RSGB 2018 Convention lecture - The Farnham WebSDR: DC to Microwaves on your smartphone

RTLion: The Multipurpose RTL-SDR Framework

Redditor [K3PWN] has recently released his project called “RTLion”. RTLion is a software framework for RTL-SDR dongles that currently supports various features such as a power spectrum plot and frequency scanning. The software can run on a Raspberry Pi 3 and all features are intended to be accessed via an easy to use web browser interface, or via an Android app. The software can also be run with Docker, making it useful for IoT applications.

RTLion project can be described as a framework due to the implementation of various features other than the frequency scanner. The common structure of the project is appropriate for adding new features too. RTLion Framework has a FlaskSocketIO based Web interface which houses it’s features there. Web interface preferred to the command line interface for facilitating the usage and supporting remote operations. Matplotlib used for creating graphs, more specifically pylabpsd(Power Spectral Density) method mostly used for converting the complex samples (stored in a numpy array) to FFT graphs.

Main purpose of the RTLion Framework is creating a framework for RTL2832 based DVB-T receivers and supporting various features such as spectral density visualizing and frequency scanning remotely. These features are provided on the Web interface and accessible via the RTLion server or the RTLion Android App for RTL-SDR & IoT applications.

RTLion - IoT RTL-SDR

All of his code is open source and available on Github. Currently he’s looking for feedback on improving the framework and we are interested to see where this project may lead in the future.

SignalsEverywhere Podcast: Is Software Defined Radio Illegal?

Corrosive from the SignalsEverywhere YouTube channel has released a new episode of his podcast, this time discussing the topic "Is Software Defined Radio Illegal?". Recently we posted about the unfortunate arrest of a UN investigator in Tunisia. Reports from news agencies seem to indicate that a major factor in his arrest was his use of an RTL-SDR dongle for monitoring air traffic as part of his investigation on Libya arms embargo violations. Although it is suspected that other political motivations are at play.

In his podcast Corrosive tries to open a discussion on whether software defined radio (SDR) is illegal, since SDR receivers have the possibility to be able to receive, demodulate and decode almost any signal. He first focuses on mostly American FCC laws regarding scanners, but similar laws are likely to be in place throughout most of the western world. Later in the podcast he discusses transmit capable SDRs and how these are more likely to come to the attention of politicians.

Software Defined Radio Illegal?

Decoding EMWIN Weather Information VHF Rebroadcasts with an RTL-SDR

EMWIN is an acronym for Emergency Managers Weather Information Network, and is a service for emergency managers that provides weather forecasts, warnings, graphics and other information in real time. EMWIN is broadcast from geostationary NOAA GOES satellites, and if you have a GOES SDR receiver setup it is possible to receive and decode EMWIN data.

However, if you don't want to set up a GOES receiver, KD9IXX writes on his blog how he investigated EMWIN and found that 24/7 dedicated EMWIN VHF repeaters are common around the US. Having found an EMWIN repeater in his area at 163.37 MHz he used the TrueTTY decoder and was able to successfully decode the 1200 baud 8-bit ASCII encoded signal and receive weather text information. He notes that VHF EMWIN is an excellent source of non-internet based weather data that could be useful to anyone requiring weather data in emergency circumstances.

EMWIN VHF Repeater Decoded with TrueTTY
EMWIN VHF Repeater Decoded with TrueTTY

Creating a DAB+ Radio Station with a LimeSDR

Thank you to Godrey L for submitting his article/tutorial that shows us how to broadcast a DAB/DAB+ radio station using a LimeSDR and ODR-mmbTools. The LimeSDR Mini is a US$159 12-bit TX/RX capable SDR that can tune between 10 MHz – 3.5 GHz, with a maximum bandwidth of up to 30.72 MHz. ODR-mmbTools is an open source DAB transmission chain which is compatible with USRP and LimeSDR SDRs.

DAB stands for Digital Audio Broadcast and is a digital broadcast radio signal that is available in many countries outside of the USA. The digital signal encodes several radio stations, and it is considered a modern alternative/replacement for standard analog broadcast FM.

The tutorial is split into four parts. The first part simply explains what SDRs are and in particular discusses the LimeSDR and how it can be used with ODR-mmbTools. Part two discusses what hardware you need, and explains what each component of the ODR-mmbTools software does. Part three gets into the actual setup of the software on Linux. Part four finishes with actually transmitting the signal and decoding it with an RTL-SDR and the Welle.io DAB decoder.

The end result is a DAB radio station with three stations being broadcast.

LimeSDR Transmitting 3 DAB stations, and receiving it with an RTL-SDR and Welle.io.
LimeSDR Transmitting 3 DAB stations, and receiving it with an RTL-SDR and Welle.io.

Receiving Es’Hail-2 DVB-S2 on Ubuntu With LeanDVB

Yesterday we posted about a real time Windows demodulator for receiving amateur TV DVB-S/S2 on Es'Hail-2/QO-100. Recently another YouTube user "M Khanfar" also submitted a video tutorial showing how to decode Es'Hail-2 DVB-S2 on Ubuntu with an RTL-SDR and the LeanDVB decoder.

Khanfar notes that although the LeanDVB decoding method is not real time, his tests show that the LeanDVB method is able to work with a much lower SNR signal compared to the Windows demodulator. The process is to simply capture an IQ file with GQRX, then run LeanDVB on the command line with the recorded IQ file. It will create a TS file that can be played in any media player.

His receiving setup consists of an RTL-SDR, 100cm dish, modified LNB and a home made bias tee that can switch his LNB between horizontal and vertical polarization.

QO-100 DVB-S2 Decoding