Clem begins by explaining how DAB signals work and why it is important to have accurate frequency calibration when receiving DAB. Later he goes on to explain the effect of sampling rate errors due to frequency inaccuracy on received DAB signals. He shows the effect of gradually increasing the sample rate error on the ability of the algorithms to decode DAB signals.
Over on his site, Clem the author of the QIRX SDR software package has written up a three part series where he explains an ultra-fast and very accurate method for calibrating the frequency offset of RTL-SDR receivers by using DAB signals. If you are unfamiliar with DAB, it stands for 'Digital Audio Broadcast' and is a type of digital radio station available in multiple countries in the world, especially in Europe. However it is not used in the USA. Clem writes:
I wrote a three-part tutorial about an ultra-fast, generally available (where you have DAB reception) and very accurate method to calibrate RTL-SDR receivers. It is called "Tutorial: Calibrate your RTL-SDR in 15 Seconds", http://softsyst.com/QIRXCalibrate?sequenceNo=0. It is using the frequency of a DAB transmitter as the reference signal, and is coming in three parts:
· Part I: Method and Measurement, describes the method (example) and compares it to two other, well-known methods.
· Part II: Checks, Frequencies, Sampling Rates: Tells how to make plausibility checks on the obtained calibration result, goes into the foundation of different measuring methods, and explains why calibrating a receiver is generally beneficial, not only for DAB purposes (where at least the frequency correction is mandatory).
· Part III: Improving DAB, Tells why it is advantageous for DAB reception not only correcting the frequency, but also the sampling rate (which is often omitted).
Part I and Part II of these are already on our website, Part III will come soon.
Welle.io is a Windows/Linux/MacOS/Android/Raspberry Pi compatible DAB and DAB+ broadcast radio decoder which supports RTL-SDR dongles, as well as the Airspy and any dongle supported by SoapySDR. It is a touch screen friendly piece of software which is excellent for use on tablets, phones and perhaps on vehicle radio touch screens.
DAB stands for Digital Audio Broadcast and is a digital signal that is available in many countries outside of the USA. The signal contains digital broadcast radio stations, and is an alternative/replacement for standard broadcast FM.
Early last year we posted about Welle.io a couple of times, but now the software has reached maturity as version 1.0 has just been released. Author Albrech writes to us:
We fixed a lot of bugs again and added the translation to Hungarian, Norwegian, Italian and French.
Binary packages are available for Windows, Linux and Android (APK and Play store). The macOS support is possible via Homebrew and we now that welle.io runs also on a Rapsberry Pi 2 and newer.
Over on the SWLing Post blog we’ve seen news of this new SDR based car radio called the Gospell GR-227. Gospell is a Chinese manufacturer of various broadcast consumer radio products including DRM receivers. It is intended to be an adapter for your car that lets you listen to digital broadcast stations such as DAB/DAB+ on VHF and DRM on UHF, but it can also be used for standard AM and FM reception. From the product sheet it looks like it will simply plug into you car USB port, and output audio through that port into your cars head unit. Control of the unit is through an Android app.
There doesn’t seem to be anything stopping someone from using this outside of a car though, so perhaps depending on the price and software hackability available it might make a good PC or Raspberry Pi based HF receiver for all modulation types too.
Over on the Gospell Facebook page are images showing the Gospell running at IBC 2017 and next to other upcoming SDR based digital broadcast receivers like the Titus II.
No word yet on a release date or pricing. The press release reads:
Chengdu, China, September 04, 2017 – A new adaptor specifically designed for in-car use that simplifies digital radio on the road will be introduced at IBC by Gospell.
GR-227 is a small, low-cost adaptor that acts as an aftermarket add-on to car stereos receiving high-quality digital broadcast programs and data application, and serving it to the car audio system over a USB cable. Based on software defined radio technology, GR-227 is compatible with DAB, DAB+, DRM and is DRM+ ready. It is also powerful enough to support digital audio decoding such as extended HE-AAC (xHE-AAC).
GR-227 literally works with any kind of car stereos with a USB port. Our patent pending technology allows the adaptor to behave like a thumb drive when plug into a USB port and makes it compatible with most of the music players not only in car but also for home use.
To make the most of GR-227, the Gospell Smart Tune App for Android has been included to add more features. When partnered with an Android powered car stereo, the App not only allows for playback of the broadcast audio program but data application which brings much fun to car entertainment.
By connecting the supplied triple band active antenna which can be attached to the windscreen through the SMA antenna connector, the reception in DRM, FM and DAB bands can be significantly improved, offering maximum flexibility between different broadcasting standards.
Installing the plug-and-play GR-227 adaptor to your car is easy and doesn’t require changing your car stereo. It is one of the easiest ways to upgrade your car radio to digital without replacing anything.
The Gospell’s aftermarket car adaptor range starts with USB model but more will follow to support more car stereo types.
Haochun Liu, DRM director, Gospell, said: “By leveraging SDR, we can now combine multiple broadcasting standards together to offer flexibility and cost advantages, coupled with easy installation without the necessity of buying a new car stereo as in traditional solutions.”
For additional information, please visit www.goscas.com or contact Gospell sales at [email protected]
Founded in 1993, Gospell Digital Technology Co Ltd (GOSPELL). is a private hi-tech enterprise with R&D, manufacturing, business consultancy and planning, trade, delivery, project implementation and after sales service, acting as a complete DTV and triple-play solution provider for Digital TV/OTT related projects. Headquartered in GOSPELL INDUSTRIAL PARK at Chenzhou, Hunan Province for CPE related production manufacturing, GOSPELL also has its office in Shenzhen for business/marketing management and administration, in Chengdu for R&D and headend/transmitter system production/debugging and Customer Service Center, and in 12 cities in China as well as international offices in India, Africa and Mexico.
Since September 2016 we’ve been slowly hearing news about the PantronX Titus II portable SDR system, but as of yet nothing seems to have eventuated. The Titus II is essentially an Android touch screen tablet running their custom software, a set of speakers, an antenna and an SDR chip with 100 kHz to 2 GHz tuning range all in one portable system that has been estimated by them to retail for less than $100 USD. The main goal with the system is to provide low cost receivers for digital broadcast standards like DRM, DAB and DAB+ to try and boost their popularity.
Titus II receiver features include:
DRM in the AM bands (MW, SW, LW) and VHF bands (FM-band, VHF band-I, VHF band-III) with latest xHE-AAC audio codec.
DAB Classic/DAB+ (VHF band-III).
FM stereo with RDS (Service Signaling).
AM with AMSS (AM Signaling Service).
Integrated service list management and service selection.
DRM/DAB Data Apps: Text Messages, Dynamic Label/DL+, Journaline, (Categorized) Slideshow, EPG, Transparent File Transmission (e.g., for educational services), etc.
Remote Radio Hotspot: Built-in WiFi hotspot feature, which allows any mobile device with an HTML5 web browser to connect to the Titus II via Wi-Fi, select radio services, listening to aud (HTML5 audio streaming) and accessing all the DRM/DAB data apps.
Recording feature and Archiving interface to select existing recordings for playback.
Titus SDR, a division of PantronX, says the Titus II multi-standard digital radio receiver is ready for production.
The consumer software-defined radio digital receiver platform, which is the result of collaboration between Titus SDR/Patron X, Jasmin-Infotech, TWR, and Fraunhofer IIS, supports multi-standard radio reception, including DRM, DAB and DAB+ and core data applications. The system is based on a custom Android tablet platform, featuring multipoint touch, WiFi/Bluetooth and stereo sound.
Titus II units will be available as a stand-alone product from Titus SDR as well as from selected OEMs. Titus SDR explains that as a module, Titus II can serve as a full-featured basis for third-party product development, adding that PantronX provided the platform and RF expertise, while Fraunhofer IIS enabled the digital and analog radio features.
With latest xHE-AAC audio codec, Titus II supports DRM in the AM and VHF bands; DAB/DAB+; FM stereo with RDS; AM with AMSS; integrated service list management and service selection; DRM/DAB data apps; text messages and Journaline.
No news yet on exact release dates, but if you are interested you can sign up to their pre-order notification list at titusradio.com.
From YouTube we’ve also found a short video of them demonstrating the Titus II from DBS2017 back in March. Another video showing the interface up close can be seen here.
Device Frontend: Manual Center Freq. Correction in kHz
Raw Recording: Playback Control, for a timed positioning (“seek”) in “arbitrary” large (GBytes) recorded raw files.
Legacy DAB, intended for users where DAB+ is not generally available, like in the UK or Spain. As this could only be superficially tested here in Germany (no standard DAB any more, I used some raw samples recorded in Madrid), I would be very interested in feedback of users about it.
Synchronization of raw files recorded with central frequency offset
Enhanced manual synchronization control, mainly for tests in mobile environments
Detection of the Transmitter Identifications (TII). However, as this is a feature only useful for specialized applications, it is not included in the distribution. To my knowledge, qirx is the only DAB SDR having this feature.
Some Bug fixing.
The QIRX team have also added a new Quickstart Guide to help users get set up with their software quickly. In addition QIRX author Clem also writes that the QIRX software will be demonstrated during this weekends Ham-Radio fair in Friedrichshafen, Germany.
The only other app that we’ve seen which is capable of decoding DAB/DAB+ on Android is Wavesink. Wavesink costs $14.90 USD on the Google Play store, but there is a free trial version available with runtime limitations and no DAB+ support.
Albrecht notes that the app is fairly computationally intensive and will require an Android device with at least 4 cores and a clock speed of 1.3 GHz to run the app. He also mentions that they are also looking for any interested developers and translators to help with development of the app.
welle.io on Android (DAB+/DAB software radio, RTL-SDR , RTL2832U)
Albrecht writes that his software is a fork of the qt-dab codebase, with the development goal being to create an easy to use DAB/DAB+ software receiver. The software is still under heavy development, and Albrecht mentions that he is looking for fellow developers and testers to help improve the software and report any bugs. Albrecht writes:
I’m proud to introduce a new open source DAB/DAB+ reception application welle.io https://www.welle.io. welle.io is a fork of qt-dab http://github.com/JvanKatwijk/qt-dab (old dab-rpi and sdr-j-dab) with the goal to develop an easy to use DAB/DAB+ reception application. It supports high DPI and touch displays and it runs even on cheap computers like Raspberry Pi 2/3 and 100€ China Windows 10 tablets. As input devices welle.io supports rtlsdr and airspy.
Currently daily Windows binary builds are available over on the projects GitHub. For Linux and Raspberry Pi users you’ll need to compile the code from source, but in the future he plans to provide Ubuntu snaps.
We gave the welle.io software a brief test and it ran as expected. There is an automatic channel scan feature which scans through all the possible DAB channels and an advanced mode for seeing technical information such as the frequency, SNR and error rates. The software also has a nice touchscreen friendly GUI which automatically downloads and displays the DAB/DAB+ program guide information.