Category: RTL-SDR

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

A Raspberry Pi and RTL-SDR Based Boombox

Thank you to Walter P. for writing in and sharing with us his conversion of an old analog boombox into a fully functional wideband software defined radio based on an RTL-SDR dongle and upconverter.

Walters Ghettoblaster RTL-SDR Radio
Walters Boombox RTL-SDR Radio

Inside the boombox Walter stripped away the analog circuitry and replaced it with a new LCD screen, Raspberry Pi, RTL-SDR, upconverter and an audio amplifier. Four rotary switches on top of the radio are used to control the frequency, demod mode and volume, and there is also a numerical keypad which can be used to enter the frequency directly. 5V and HF antenna connectors have been added to the side, as well as an upconverter enable switch on top. Walter also added a Spyserver mode to the software, which allows you to connect to the radio over WiFi with SDR#, although he notes that using the integrated Pi WiFi module seems to introduce noise on the speakers.

If you're interested in building a similar device, Walter has provided the full Python code and installation instructions for his build.

Edit 09 May 19: It was pointed out that the word "ghettoblaster" could be considered offensive in some cultures. We have changed the word in our article to "boombox" and apologize for any unintended offence.

RaspBRadio - ghettoblaster with sdr radio scanner inside

Windows Realtime DVB-S Demodulator for Es’Hail-2 & Amateur TV Available

Thank you to Happysat for writing in and noting that over on the Amsat-DL forums user Markro92 has uploaded a realtime Windows DVB-S demodulator with GUI. The demodulator works with the RTL-SDR, HackRF, SDRplay and PlutoSDR support is due to be added soon. Happysat notes the following: 

It can demodulate DVB-S and S2 signals with very low symbolrate on Es Hail-2 geosat on 25,9 East from the Wideband Transponder. So you do not need a modified lnb or modified satelitte stb :) Of course you can also see the amateur tv streams which people uplink theirself.

To see if there is any stream active one can visit the wideband WebSDR and above the stream the info is displayed which parameters in use (symbol rate and mode dvbs(2)) so you can adjust in the Demodulator program. Stream + Chat: https://eshail.batc.org.uk/wb/ .

The latest version of the software will always be always available at http://v.1337team.tk/dvb-s_gui_amsat.zip.

Happysat Decoding a DVB-S2 stream from Es-Hail2 with an RTL-SDR V3.
Happysat Decoding a DVB-S2 stream from Es-Hail2 with an RTL-SDR V3.

United Nations Expert Arrested in Tunisia for Using an RTL-SDR

Recently several newspapers [CNA] [France24] [Guardian] [MEM] [HuffPostMG] have reported a story about a United Nations (UN) expert being arrested in Tunisia for having an RTL-SDR dongle. Dr. Moncef Kartas is a member of a UN panel of experts investigating violations of the UN arms embargo on Libya. 

On March 26, 2019 Kartas was arrested on his arrival in Tunisia on suspicion of spying for "unnamed foreign parties", and one of the key arguments being used against him is that he was in possession of and had used an RTL-SDR dongle. In the France24 article, they explain that he was using the RTL-SDR as part of his investigation for monitoring air traffic to Libya in an attempt to link flights against violations of the arms embargo. 

As Kartas' business in Tunisia was to present his findings on the arms embargo violations, other experts believe that the arrest is politically motivated, and that ownership of the RTL-SDR for espionage is simply being used as an excuse. However, while the investigation continues Kartas remains in jail, and in Tunisia a charge of espionage could be punishable by death. As Kartas holds UN diplomatic immunity, and as Tunisia is a member of the UN, the arrest and detainment is seen as illegal.

We hope that Kartas is safe and will be released soon. If you want to keep an eye on his story, there is a Twitter account called "Free Moncef Kartas" @FreeMoncefK that appears to be posting news articles and tweets about his arrest.

Human Rights Watch Denounces the arrest of Moncef Kartas
Human Rights Watch Denounces the arrest of Moncef Kartas [Photo Source]

Weather Satellite Images from Geostationary COMS-1 Received

COMS-1 Geostationary Satellite Footprint
COMS-1 Geostationary Satellite Footprint https://www.wmo-sat.info/oscar/Satellites/view/33

COMS-1 is a geostationary weather satellited operated by the Korean Meteorological Agency (KMA) which was launched back in 2010. It is similar to NOAA GOES satellites as it is also geostationary orbit (@128.2°E - footprint covers all of Asia + AUS/NZ), and so is far away enough to image the entire disk of the Earth at once. Unfortunately, unlike the GOES satellites which have in the past few years become relatively easy for hobbyists to decode, the COMS-1 LRIT and HRIT downlink data is encrypted by KMA. KMA only appear to provide decryption keys to governments, research institutes and large organizations upon request.

However, recently Australian @sam210723 was able to successfully create code to decrypt the key message file and obtain the images. From a previous Twitter post of his, it appears that the encryption keys from the KMA example code are actually valid and can be used without needing to apply for a key.

Sam notes that he'll soon release a full blog post on his results, but for now he has an older post from last year that explains a bit about the satellite and decryption of the LRIT Key. His code is available on GitHub, and in a recent Twitter post he shows some example images that he's been able to receive using an Airspy SDR.

Using an RTL-SDR and OpenCV To Create an EMI Heatmap of Circuit Boards

Over on YouTube and his blog user Charles Grassin has uploaded a short video and blog post showing how he's using an RTL-SDR EMI (electromagnetic interference) probe and OpenCV to create a visual EMI heatmap.

Earlier this month we posted about Dmitris' experiments in which he was able to create a home made EMI/EMC probe out of a loop of semi-rigid coax and an RTL-SDR V3. This type of probe is useful for determining what components or areas on a circuit board are emitting electromagnetic interference. EMI testing for PCBs may be critical for passing compliance tests.

Charles' project takes the RTL-SDR EMI probe idea a step further by combining it with OpenCV. OpenCV is an open source library of code for computer vision applications. With the EMI data generated by the RTL-SDR EMI probe, and a camera pointed at a PCB, Charles is able to overlay a heatmap on top of the visual image which reveals the EMI hot spots on a PCB.

The video below shows the EMI heatmap of an Arduino PCB being mapped out. His blog post shows some other examples like a keyboard and a hairpin RF filter. The code he's created is open source and available on his EMI_Mapper GitHub page.

EMI mapping (OpenCV and RTL-SDR)

KerberosSDR Batch One End of Stock, Batch Two Preorders Available

If you weren't aware, KerberosSDR is our recently released 4x Coherent RTL-SDR which can be used for tasks such as direction finding and passive radar. KerberosSDR was successfully crowdfunded over on Indiegogo, and we have recently completed shipments to all backers. Currently there is only about 20 units of the batch one production left in stock.

We are currently offering discounted preorders for batch two units on Indiegogo which we expect will be ready to ship in July or hopefully earlier. If you are interested, please order soon to avoid missing out as the price will be raised again once we are shipping. Batch two will be the same as batch one except for some minor changes. For example we have decided to convert the microUSB port into a USB-C port as we have found that there are many very poor quality microUSB cables on the market which could cause issues for users. USB-C cables are generally of a higher quality.

More information about KerberosSDR is available on the Indiegogo page.

KerberosSDR Updates

Since our last post on this blog about KerberosSDR we have made some enhancements to the software.

  • The KerberosSDR code is now fast enough to run at 1-2 Hz update rates for direction finding and passive radar on a Raspberry Pi 3 B+.
  • There is now a web interface, so the KerberosSDR can be controlled via a WiFi hotspot and internet browser. Useful for use on the Pi 3 and Tinkerboard.

For future updates we are currently working on several new features:

  • Filters to remove low confidence DoA results on the Android app.
  • A secondary heatmap type display on the Android app based on signal strength, for two direction finding indications.
  • Methods to determine the center of multiple bearing intersection points.
  • Further enhancements to processing speed, possible improved results from processing gain and possible better accuracy from improved DoA algorithms.

Within the next few weeks we will also release full tutorial videos that will show how to set up and use the KerberosSDR for direction finding and passive radar with a Raspberry Pi 3 or Tinkerboard. If you prefer a text based explanation we already have a guide up at rtl-sdr.com/ksdr.

Below is an image that demonstrates the KerberosSDR direction finding Android app. A user of KerberosSDR has also submitted two of his own screenshots that show that he was able to determine the location of a GSM transmitter with a linear antenna array.

KerberosSDR Direction Finding Results
KerberosSDR Direction Finding Results. Multiple data points collected during a drive, with bearings pointing towards the TX tower (red marker). Circular array of whip antennas used at freq. 858 MHz.