Tag Archives: Decoder

AirSpy: How to listen to DAB+ Broadcast

It’s pure fun to listen to N-Joy, a North-German broadcaster, in DAB+. This digital mode should replace all classical FM broadcast, and has already done this in some countries where others offer both – like Germany.

DAB+ takes place in former TV bands. Several stations are bundled in a bouqet. In Germany, one usually is in comfortable reach of at least one of these bunches, see footprint on a map, with stations around my location:


Footprint of DAB+ broadcasts in Germany. Pin = my location. In the list you see the stations plus the channel (“bouquet”), here 5C omnidirectional from Hannover with 10 kW and 6C, also from Hannover, but pointed to the east, with 8 kW.

As AirSpy is covering also these frequencies with high sensitivity and a decent dynamic range, I gave it a try.

First software used is called Welle (English: wave) by a team around Albrecht Lohofener. I use it on a PC/W10. It’s easy to install, and then start it by the usual double-click. An MS-DOS windows opens, starting a routine for searching and opening the AirsSpy connected to your PC. This window informs you on all steps the software is doing.

Then the graphical user interface starts. First you have to scan the bands: click “Sendersuchlauf -> Start” (the software detects on what country code your OS is running and switches automatically to e.g. English), see screenshot:


The scan is running, 13 stations have been found so far. With expert mode (“Expertenmodus”) activated, you see the spectrum of the frequncy set being scanned.

From the spectrum (right), you might see if HF gain ius ok, or that you should go from automatic (“Auto HF-Verstärkung”) to manual gain control (“Manuelle Versätrkung”) to either imporve sensitivity or to avoid distortion due to strong transmitters nearby. With me, “Auto” drives fine.

After finishing the scan, “Welle”  comes down with the bouquets in reach:


Just click your station from the list on the left, and the station will be heard. Many of them provice additonal information, as here MDR Sputnik with weather. On the right you again see the spectrum of the whole bouquet (6B, 183,648 MHz) plus additional information an the quality.

Secondly, a more technical approach is offered by Jan van Katwijk with also free Qt-DAB. I also use it on my PC/W10. After downloading the suite, containing also other intersting software, just start “qt-dab-0.999”. An MS-DOS windows opens, followed after some seconds by the GUI. Here you have to define the receiver from a drop-down list, choose the boquet (5C, in this case), and scanning serves you the stations’ list. You may have up to five different windows open – from the MS-DOS window to more detailed technical data, including a QPSK phase window, right from the spectrum.


Qt-DAB presents you with up to five windows: MS-DOS on top; gain control main window and technical data below, and spectrum plus QPSK phase constellation at the bottom. “Klassik Radio” on 173,352 MHz playing Bach: “What God does that is done well”. Not to talk of what the authors of the DAB software had done …

Thanks to both, Albrecht and Jan, to have developed this fine piece to software, free of charge!

SDR Transceiver Zeus ZS-1 and Digimode Software FLDIGI

A strong combination: State-of-the-Art SDR transceiver Zeus ZS-1 and digimode software FLDIGI. with this insutrction, the combination of both with audio in/out, keying and freqeuncy transfer is easy.

A strong combination: State-of-the-Art SDR transceiver Zeus ZS-1 and digimode software FLDIGI. With a step-by-step instruction, the combination of both with audio in/out, keying and freqeuncy transfer is easy.

With software-defined radio or SDRs, also ham radio has made a considerable leap forward. SDR transceivers are around for many years but failed to have a major impact until now. Among these transceivers, Russian and German-made Zeus ZS-1 is an outstanding example, covering each amateur radio band from 160 m to 10 m with up to 15 watt output. It received enthusiastic reviews around the world, e.g. by RadCOM of RSGB and QST of ARRL with excellent ratings.

Recently, I again bought on ZS-1 to re-vitalize my amateur radio activity with also again a focus on QRP and digital modes. For this purpose, ZS-1 with its outstanding clean signal under transmit and Receiver plus tidy interface is almost ideal. BUt Ehen I needed a fool-proof instruction to set up the combination of ZS-1 and a multimode software like FLDIGI, I didn’t found what I need: a step-by-step approach.

This was the reason for writing such an instruction by myself. I concentrate on the combination of ZS-1 and FLDIGI which in a PDF is laid out in detail and with instructive screenshots. In an appendix, I go also through some other digimode software like FreeDV and EasyPal. To my own disappointment, I couldn’t get work WSJT/WSPR. So your help is very appreciated!

You can download the 20-paged PDF with its 24 screenshots right here.


PC-HFDL Display: Receive, decode and analyze the biggest net on HF!

HFDL is a net for data communications between airplanes and ground. The results can be shown on Google Earth . This screenshot shows a part of 29.000+ entries, received and processed on August 15th, 2016.

HFDL is a net for data communications between airplanes and ground. The results can be shown on Google Earth. This screenshot shows a part of 29.000+ entries, received and processed on August 15th, 2016.


Communications between air and ground is mostly done on VHF, UHF and SHF. But if an aircraft is out of reach of a ground station station due to the limited “radio horizon” of these bands, it has to maintain communications by either satellite or HF. This HFDL net is in fact the most massive professional user of HF right now. Within 24 hours, I get more than 40.000 live messages with a modest equipment.

With his software Display Launcher, Mike Simpson from Australia provides a most valuable tool to analyze up to nine channels in parallel. His software also draws positions and routes onto Google Earth. Mike has spent much energy on coping with many inconsistencies of transmitted data before it all really goes smoothly.

This free software is the vital part of a monitoring project to receive, demodulate and analyze live up to nine HFDL channels in parallel. Other ingredients you need is a software-defined radio (SDR), nine virtual audio cables (in fact, a piece of software) and a decoder software. Don’t forget an antenna and a PC …

This setup comprises a semi-professional monitoring station which will allow you to receive and track many of the nearly 3.000 airplanes using HFDL. This also covers the military, business jets, helicopters and some other delicate users. It maybe used as an important complement to Flightradar24’s web service, whenever their VHF/UHF/SHF-based net is out of range of the aircraft. This is particularly true over vast water masses like oceans and sparsely populated land masses. Furthermore, Flightradar24 erases some sensible flights from the raw material before publication on their website. This is clearly no “censorship”, but some thoughtfulness in regard to those countries where reception and publication of HFDL data is more tolerated than explicitly encouraged by the government.

In a 9-page PDF, I published a step-by-step recipe on how to set up such an HF monitoring station for up to nine parallel HFDL channel. You can download it here.

Wake up – ICAO Selcals

If you ever had an ear on the aero bands, you are already familiar with ICAO Selcalls. With this 2 x 2 tone signal lasting for about 2,2 seconds, a Ground Station alerts a specific airplane to open up for communications. The short video on top of this page shows a typical initial contact, where Ground an Air are testing the Selcal.

This paper (click this hyperlink) describes on three pages with nine illustrations, one video and one audio the procedure and gives some background information. These may improve correct decoding of the somewhat delicate signals, as it will show how to look up the Selcal and follow the flight. BTW: It is planned to extend the pool of 16 tones to 32 tones by September 1st, 2016.

P.S. Remember to save the PDF and open it with a recent version of Acrobat Reader. Otherwise the multimedia (video, audio) will not work!

20 MHz HF: “HackRF One” on Shortwave

world Kopie

The world is full of software-defined radio (SDR), but HackRF One has a rather unique position – thanks to its vast maximum bandwidth of 20 MHz. With an up-converter, this combination covers more than 70 percent of the whole HF range from 3 to 30 MHz. Even better: with proper software you can record and play this enormous band!

However, this stunning bandwidth is achieved by a moderate resolution of 8 bit, resulting in a dynamic range of just nearly 50 dB. Or the half of SDRs like Elad’s FDM-S2.

Anyway. I wanted to know in practice what you can actually do with such a set at a budget price plus mostly free software. The results surprised even me: Properly used, this combination convinced as a quite decent performer on HF! The world map above shows some of the stations received with the set (see insert bottom left) to test its performance.

I laid down my experiences and recommendations for best reception in a paper of 17 multi-media pages full of examples – including 55 screenshots, 21 audio clips and one video. The PDF shows how to optimize reception of broadcast, utility and amateur radio stations. It covers many examples on how to analyze recordings, to decode data transmission with free software plus live decoding of 14 channels in parallel. It also gives some examples of combining HF reception with the internet, e.g. regarding the reception of signals from airplanes (ARINC, HFDL) and vessels (GMDSS).

My experiences really left me enthusiastic about this set.

You may share this enthusiasm and download the PDF of 43 MB here. Save it on your hard disk or USB stick, and open it with a most recent Adobe Reader. Otherwise, the multimedia content will not work.
[Einen deutschsprachigen Test  habe ich jeweils als Titelgeschichte in der April- Ausgabe 2017 der Fachzeitschrift  Radio-Kurier – weltweit hören und in der Mai-Ausgabe der Fachzeitschrift Funktelegramm veröffentlicht.]

Multi-Channel Monitoring


In recent posts, I already wrote about my experiences with Simon Brown’s software SDR Console V3.0. It matches most SDRs, delivers now up to 24 virtual receivers and is capable to run multi instances, i.e. you may run several SDRs on one PC in parallel.

That’s exactly what I did when I connected three SDRs FDM-S2 to a PC, running 35 different ARINC-635 channels in parallel resulting in 68.000 decoded messages. It worked brillantly.

And there is much more, e.g. recording and playing 24 audio channels from broadcasters throughout 20 MHz (the whole FM band!) with hardware RFHack One.

This paper provides a hands-on and step-by-step guide for some vital monitoring tasks like:

  • using up to three receivers on one antenna and one PC
  • working with multi instances of GUIs
  • working with multi instances of software decoders like PC-HFDL and MultiPSK
  • carefully planning a monitoring session
  • analyzing  the decoded results and apply some basic statistics on 68.000+ messages
  • record and play 24 channels incl. RDS data within a bandwidth of 20 MHz on the FM broadcast band plus on HF with RFHack One (see screenshot on top of this page, “Matrix” mode)
  • … and much more

24 channel in parallel: Simon did it again

24 virtual channels in sizeable windows of 24 kHz width each - also zoomable.

24 virtual channels in sizeable windows of 24 kHz width each – also zoomable.

In a sneak preview of his SDR software “SDR Console”, Simon Brown again presented all SDR enthusiasts with again another major achievement: up to 24 independent virtual receivers!

Called “Matrix”, and beautifully layouted, each virtual receiver can be placed within the bandwidth of an SDR, i.e. about 5 MHz using an FDM-S2 by ELAD. Each virtual receiver may carry it’s whole individual settings of e.g. mode, bandwidth and AGC.

I also tried out three instances of this software in parallel with three FDM-S2 to cover 15 MHz with 72 indvidual virtual receivers. Their output may be fed to recorders and/or decoders via virtual audio card.

See this introductory paper for a first view. It shows in praxi how to use this stunning feature to tune into 24 broadcasters in parallel, record and play their transmissions. More to come, e.g. examples with of monitoring with decoders.

« Older Entries