An Über-Decoder for the Professionals


Our regular Utility DXing columnist undertakes a privileged excursion to the lofty realms of professional-level signals intelligence


Our regular Utility DXing columnist undertakes a privileged excursion to the lofty realms of professional-level signals intelligence, looking at the established, specialised, software decoder Wavecom W-Spectra.


As hobby listeners, we often look – not, perhaps, without some envy – at some of the expensive and very sophisticated, tools the radio professionals use for their daily monitoring tasks. In this overview, I would like to take a hands-on look at some of the software developed by the Swiss company Wavecom AG.

This company was founded in 1985 by Christian Kesselring. Christian was a charismatic pioneer who developed both decoding hardware and software of a professional standard, at a comparatively low price.

In his first years of business, he found customers among demanding listeners as well as among price-conscious professional customers. After a while, he decided to serve mostly the professionals.

In early 2009, Christian appointed Dr Junli Hu, a smart engineer from the renowned academic institution ETH (Eidgenössische Technische Hochschule) in Zürich to the post of MD at Wavecom.

Sadly, Christian passed away in 2015. However, Junli subsequently developed the company and its products, in conjunction with his team.

Wavecom products include professional decoders for modes so intelligence-sensitive that they require an End User Certificate (EUC) relating to ‘goods for surveillance purposes’.

The Wavecom range of professional-level tools covers not only decoders like the (all-software) W-Code but also hardware such as wideband PC decoder cards for up to four channels as well as embedded systems.

I have been an avid user of Wavecom decoders from the days, when Christian Kesselring developed them for his former employer, Poly Electronic, back in 1984.

Nowadays, I mostly use the latest brainchild of Christian, Junli and his team: W-Code.

This piece of advanced software is in use in many thousand installations around the world. It is also deployed by the monitoring system (‘Intruder Watch’) of the International Amateur Radio Union (IARU) as a professional link between IARU’s own surveillance (of intruders in the amateur radio bands) and the monitoring undertaken by official authorities.


New Horizons

With W-Spectra, Wavecom has, arguably, opened up a whole new level of operation, in a league of its own (Fig. 1). The system is a completely automated monitoring solution; you only have to add a receiver like the Winradio G3xDDC Excalibur Pro or a Wavecom PCIe receiver.

The software combines all its key functions in just one Graphical User Interface (GUI). Here, users can control the receiver, which then classifies and decodes signals autonomously.

To this end, the program provides a configurable dataset. To many users, this combination is much more powerful than just adding software after software by yourself.

As I can only scratch the surface of the many features of this software, a typical workflow might be helpful to give some impressions.

There are three different monitoring modes: Direct Mode, Memory Scan and Frequency Search.

The first one of these most resembles our work as DXers.

A slice of 2MHz, out of the range of the receiver, is presented in one window. In its lower half, a narrowband display, showing 24, 48 or 96kHz bandwidth, allows for a closer, more detailed, inspection of signals (Fig. 2).

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Classifiers and decoders work automatically and in parallel.

The term ‘classifying’ means that W-Spectra detects and measures the key parameters of each signal in a given range, for instance its modulation type, baud or symbol rate, carrier frequency, the number of carriers, the shift or signal bandwidth, carrier spacing and more.

This highly sophisticated tool can, therefore, save its users a lot of time. The program both supplements and extends the knowledge and experience of its operators and it works unattended.

In what sounds like sorcery, with any given signal, the decoder is selected completely automatically, prior to the actual decoding of the signals. The software has more than 220 decoders on board, from old-fashioned Morse code (still in frequent use by the Russian Navy, among others) to more recent bread-and-butter modes like Automatic Link Establishment and STANAG4285.

There are decoders too for more sophisticated areas like PACTOR-4 and a couple of proprietary CODAN modes, relating to a popular range of transceivers from the Australian company of the same name (Fig. 3).

 And these are only just the modes used on HF. Decoding of a realm of modes used above 30MHz is also possible (DMR, PMR, TETRA, TETRAPOL and so on) as is the decoding of satellite signals such as from INMARSAT.


Amateur v Professional

In a nutshell, the conspicuous difference between a highly professional system like this one and the listening activities of an interested amateur is that the specialists conduct their monitoring activities on an automated base. Consequently, they have at their disposal a much wider selection of modes.

In practice, this works just fine and professional observers can get very reliable results in a short time. The experts are needed and come into their own, where signals are very weak or of a ‘non-standard’ nature.

In other words, the goal of these professionals is not to ‘catch the most fanciful DX’ but to solve a specific problem. This could be, for instance, the monitoring of all communications on the Balkans or in other, geopolitically sensitive, regions of the globe.

In most cases, experts can rely on strong one-hop signals on HF, either from their own (national) receiving stations or from remote receivers (‘sensors’, in ‘monitoring-jargon’) near, or even inside, a region of interest.

In addition to Direct Mode, W-Spectra offers Memory Scan and Frequency Search (Fig. 4).

In the former, the software quickly moves from one memory channel to the next, in order to check activity.

Frequency Search is an efficient tool for automatically tuning across a defined range. For example, users can observe the entire HF band from 3 to 30MHz, in pre-defined steps.

The software allows monitors to record any signals found and classified into its database. In many situations, this is preferable to automatically populating a database in a new band or at a new location.

Professional monitoring is very much about patterns – in modes, nets, times of operation and so forth. Therefore, an integrated documentation is mandatory. Software W-Spectra offers this, by automatically writing each result – including its ‘meta-data’ – into a database. This can be searched by individual criterion.

The more data there are, the better this pattern-recognition works. This method further emphasizes the importance of a fully automated approach, in order to continuously deliver reliable data of fine granularity.

The screenshot in Fig. 5 shows an ‘activity-scan’, ranging between Memory Channels 2 and 452.

Even with all this technology, manual searching by a monitoring expert is an important aspect of surveillance. In this context, W-Speed (Fig. 6) is an integrated spectra editing tool. It displays an IQ recording as a spectrogram, with selectable display bandwidths from 250kHz to 24MHz. On it, you can easily see each activity at a glance, to further analyse and investigate it in greater detail later. By doing so, you won’t miss even short-lived transmissions; neither will those otherwise elusive ‘frequency-hoppers’ escape your attention.

Wavecom W-Spectra and its accessories is mightily impressive, ultra-professional-level, technology and it comes at a price. Around £23,000 will buy you the software for the whole monitoring system, including W-Spectra, W-Speed, a wideband classifier and all decoders.

Well, we can all dream….

This article was featured in the July 2018 issue of Radio User