Since August 2021, the RTL-SDR Active Patch Antennadelights the community worldwide. It is small, yet highly efficient. With RTL-SDR Dongle and some software, it combines to a surprisingly high performance receiving post for INMARSAT, IRIDIUM (which I first used with a mobile phone 20 years ago on a tour through Mongolia and China with stunning quality), and GPS – all for just about 100 US-$.
Plug the USB stick into your PC, connect the patch antenna to the stick’s by a cable and set it on a flexible tripod (all contained in the set!), and the sky becomes open. In the screenshot below, I used the nuandRF to show at least half of the bandwidth of the antenna, because this SDR covers 60 MHz:
Aero makes a good start with powerful signals and free software JAEROwhich can also run in multi instances to cover all the channels in parallel.
You may also set sails for some maritime experience with the std-C Decoder (full version: 55 US-$). It even visualizes e.g., buoys and areas (rectangle, circle and free format) a Open Street Map.
You may also receive the GPS C/A code signal on 1.575420GHz, and IRIDIUM on which John Bloom wrote the pageturner “Eccenctric Orbits – The Iridium Story“, which I can only highly recommend as a truly thrilling backgrounder. As low-orbiting satellites, the channel has to be handed over to another satellite after about nine minutes.
The RTL-SDR Active Patch Antenna is a great, little tool providing high SNRs at a small form factor of 17.5 x 17.5 cm. Its low noise amplifier (powered via bias tee from the SDR stick) together with the SAW filter to suppress any signals outside its passband from 1.525 to 1.660GHz shows unsurpassed performance at this price tag. It is a must, and absolutely a no-brainer. Did you miss a large suction cup to mount it on your window? Wait a minute – it is also included in the turnkey package …
In my last blog, I wrote about my experiences with BCS-GMDSS multi-channel decoder. Chris, the software author, had added some smart features in the meantime. I would like to briefly introduce some of them in loose order.
Newly introduced is a window showing “Frequency and Time Statistics”. This somewhat sober, albeit highly informative table can be spiced up a bit yourself – see the following three screenshots (double-clicking onto them shows them in full resolution):
The heatmap shows clearly that 8MHz is the most productive channel. It shows also how propagation works – see fade-in and fade-out of those channels on 12MHz and 16MHz. From a DXer’s point of view, however, 2187.5kHz can be considered some of the most interesting channel. Another new window gives an overlook about all those Coastal stations received, and how often, on what channel, and when for the first/last time.
Furthermore, Chris introduced a (basic) map where you can see the locations of those Coastal stations you have received – if you don’t know exactly where to locate e.g., Taman Radio or Marzara del Vallo Radio … Even better, as the map is living: double-click to a location, and a window with your logs of this Coastal is popping up!
The log is organized as a database. This opens the chance for many applications in logging, searching and presenting your logs. Many of those option are already built-in, like searching all stations within a specific time frame or matching one or more specific fields, let it be MMSI, Ship Owner or country. One special format supports that used by highly recommended firstname.lastname@example.org:
The recent version of BCS-GMDSS also supports a search option for MMSI: just double-click the wanted MMSI to open a specific Google search. In nearly all cases I tried, the first result lead straight to much more information on a handful of websites, providing e.g., location, map with position and often a photo of the vessel:
Finally, Chris was kind enough to respond to the request of a single, elderly gentleman and provide for the export of all data in a form that separates all possible data fields by CSVs – analogous to the official ITU publications, among others. This offers many more and very specific possibilities for search and (statistical) evaluation. The nice elderly gentleman has already tried this (“Great!”) with Access:
After so much data then for writing reception reports with some nice results:
Chris Smolinski, W3HFU, did it again: after his multi-channel attack to ALE, he now offers this highly innovative concept also for GMDSS – Black Cat GMDSS. In addition to an extraordinary sensitive decoder, it also includes smart processing of the data – from looking up vessel’s complete data from ITU’s Ship Station List (internet connection needed) to saving all data to a fully-fledged database. Welcome aboard! Now let’s set sail!
3000+ Messages a Day – received on HF
The Global Maritime Distress and Safety System is a system of different maritime communications tools on frequencies ranging from as low as 424kHz [NAVTEX] over HF and VHF up to satellite channels in the GHz region. This blog entry focus on Black Cat GMDSS decoder, hence on HF. There, the six main channels range from 2MHz to 16MHz. Reception of both, Coastal Stations and vessels, is from around the world. In this case from Vestmannaeyjar Radio in Iceland to Cape Town Radio in South Africa, and from Valparaiso Playo Ancha Radio in Chile to Taupo Maritime Radio in New Zealand. You may hear vessels of each and every kind, from small ones for pleasure to the biggest oil tankers, and all over the world. Monitoring on all six main channels in parallel, often raises 3000+ messages a day!
Robust FSK mode
Transmission is done in 2-FSK with 170Hz shift and at speed of 100Bd. Waveform is ‘kind of SITOR-B, repeating each character twice with a 400ms spread to enhance proper decoding under adverse propagation (Rec. ITU-R M.493-11). To establish a call, each station has been assigned to an unique MMSI, or Maritime Mobile Security Identity number consisting of now nine digits, in future 10 digits. MMSIs starting with 00 denote a Coastal Station, e.g., 004123100 for Guangzhou Radio/China. There is a set of 127 symbols, with the first numbers 00 to 99 representing numbers, and each of the remaining number specific situations like “110” denoting “Man over board”. The software has to look up those source-coded messages in a codebook to print a readable message, giving some sense.
One message is about 6.4 seconds long. it starts with a short dot-pattern/phasing sequence for automatic tuning, followed by the content. In this live example, JRCC Australia (MMSI 003669991) is calling Merchant Oil tanker Signal Maya (MMSI 248410000) on 12577kHz at 15:59:43 UTC on November 21, 2021. There are transmitted 23 groups (“Symbols”) in GMDSS :
021 007 061 000 000 -> Address – MMSI of called station
108 -> Category
000 050 030 000 010 -> Self MMSI – MMSI of calling station
118 126 -> first and second [none in this case, “idling”] telecommand message
126 126 126 -> frequency message [none in this case, “idling”]
126 126 122 -> end of message
111 -> error-check character [ECC]
After a look-up in the codebook this turns into:
Format: Individual call
Address [to]: 210761000
Self MMSI [from]: 005030001
First telecommand: Test
… even smarter decoding!
Still not much enlightment. But BCS-GMDSS is at your service. It looks up all the cryptic numbers at different sources, even tapping official ITU webpage to enrich the vessel’s MMSI with its stunning mutltitude of information. Wrapping it up, decoding and looking-up in an internal codebook (Coastal Station) as well as in ITU sources (vessels), the above mentioned 23 symbols come out in full glory reading:
[2021-11-21 14:59:43] 12577 Symbols: 120 120 021 007 061 000 000 108 000 050 030 000 010 118 126 126 126 126 126 126 126 122 111 Self MMSI: 005030001 – Australia – JRCC AUSTRALIA 26 20′ 48″ S 120 33′ 52″ E 13669 km, 92 deg Address: 210761000 – Cyprus Ship: SALT LAKE CITY | Callsign: C4DS2 | MMSI: 210761000 | Cyprus (Republic of) (CYP) | Vessel ID: 9314129 | EPIRB: BE1 | 06/12/2017 Class: Merchant | Bulk carrier | | 89076 tons | 26 persons | INMARSAT C MINI M INMARSAT M VHF DSC | 24 hr service Owner: NOBEL NAVIGATION CO LTD POB 50132 LIMASSOL CYPRUS Misc: Former Name: THALASSINI NIKI | | EPIRB ID: 210761000 | | Telephone Bands: STUV | AAIC: GR14 | | CO | | Format: Individual call Category: Safety First telecommand: Test
As you have seen, I already mixed some theory with some practice – as you know me.
Now for some features of the software, plus some hints to make the most out of it.
Some basics, you must be tuned to
BCS-GMDSS offers up to 8 channels in parallel which by default are set to the main six GMDSS channels plus two with only rarely traffic observed, also on 2MHz. Those channels are fed by a SDR, ideally covering the whole range from 2MHz to 17MHz, alias-free. In this range you have to place the up to eight channels, RX1 … RX8, and have their output set to VAC1 … VAC8. The inputs of the decoder have to match those VAC numbers – see screenshot.
Take some care to think about mode, tuned frequency and audio frequencies, and bandwidth. Mode can be USB, CW-U or FSK, whatever your SDR’s software offers. It is, however, mandatory that the center frequency of the audio output must match the centre frequency of the input of the decoder! Otherwise there will be no decoding.
I am using free SDRC software by Simon Brown, G4ELI, easily providing all eight channels via VAC software. I am using CW-U and a bandwidth of 400Hz, giving some room for stations which might deviate by some 10Hz from the assigned channel – the decoder automatically compensates for this. With this setup (see screenshots below), the frequency readout shows the assigned channels, plus centre frequencies of decoder and receiver are matching (here 1700Hz, as ITU recommends). The bandwidth offers a good balance of SNR and tolerance for stations with a slight offset. Your mileage may vary in some aspects, e.g., you may prefer SSB-USB mode, or your software has a BFO if you use CW … You may also use the wrong sideband (LSB instead of USB) with your receiver – but than you just have to tick “Invert” in the decoder’s Setting menu as it then changes Mark and Space frequencies.
Order! How to cruise through this Ocean of Messages
BCS-GMDSS cleverly combines a most powerful decoder with some extras to calm the rogue waves of decoded information. First, you may reduce (or extend) the degree of information you fetch form the ITU page: Edit -> Settings -> MMSI Lookup. It is very interesting to see the maximum of data (“Most Details”), but with everyday’s monitoring just “Basic” or “Detailed” may run the show. This creenshot is showing the differences:
The second step is to distinguish the vessels from the coastal stations by color. I set the latter ones to show up in blue:
Next, BCS-GMDSS offers a Coastal Station’s database. It is a real database which, e.g., each column can be sorted. In the screenshot below, I had sorted them according to their total messages received. Then “Yusa Radio” has been double-clicked to inspect the timestamps of reception:
The “Loggings Database Search” is like a supertanker, containing all your logs which can be sorted by a double-click, plus being queried for each column, also combining different criteria. This is the most powerful database any GMDSS decoder has on board. See screenshot below for just one example:
Addendum: Where are they cruising?
The location of most Coastal stations is openly available, and their geographical coordinates are internally looked up by the software – even calculation of the distances to your location (Edit -> Settings -> Latitude:/Longitude:) is done automatically. But where are the vessels cruising? They only rarely transmit their location in GMDSS on HF. But if they have an AIS, or Automatic Identification System, you have a fair chance to get the actual location. This system comes in two tastes: AIS and LRTI, or Long Range Identification and Tracking. AIS is using VHF. Propagation restricts the range to some ten kilometers. LRTI is using satellite (INMARSAT). There are some webpages where you get at least AIS for free – just to mention VesselFinder, VesselTracker and MarineTraffic. Their business model is to offer subscriptions for one year at a price of about 1’200 US-$ for LRTI (satellite) data, aimed mainly to the professionals. But most of those companies offer (limited) access to their AIS data for free. The two screenshots below show the difference.
The example above, bulk carrier Salt Lake City, is only availabe on LRIT. So free data are about one week old. Nevertheless, you get at least a clue where the ship had been. And if time plays no role, just look it up exactly this week later …
If you have received the following message, you are lucky:
[2021-11-22 17:02:38] 2187.5 Self MMSI: 229375000 – Malta Ship: CMA CGM FORT DESAIX | 9HA5478 | 229375000 | MLT | MLT | 9400174 | 229375000 | 04/08/2021 Address: 002275300 – France – MRCC CORSEN 48 40′ 60″ N 2 19′ 0″ W 947 km, 252 deg Format: Individual call Category: Safety First telecommand: Test
Morse Code or CW has become rare among professionals (in the West). But there is a busy net of small Japanese Fishery Stations literally pounding the brass. One of them is Kagoshima Radio, JFX. They are not daily heard in Europe, but a combination of receiver Winradio Sigma, active antenna MD300DX (2×2.5 m, vertical) and SDRC V3 software did the trick even under this grim summer propagation. See screenshot above, from 24 hours’ recording of 25 MHz HF. All channels clearly readable – as far as the expressive handwriting (see detailed screenshot at the bottom) of their CW allows for … Yeah: CQ CQ DE JFX JFX QRU QSX 6 / 8 /12 MHz K
Some days ago, I wrote about my very first experiences with Winradio’s groundbreaking SIGMA SDR receiver, covering e.g. the whole HF band with 32 MHz width and 16 bit resolution – plus much, much more. SIGMA comes with a fine software, and provides an API.dll for connection to 3rd-party software. Thankfully, Simon Brown, G4ELI, adapted his unique SDRC V3 software to this (and other) Winradio in nearly no time.
This combination has become a real dream team: the best hardware and the best software avalaible. The screenshot at the top shows just one example of others which will follow: I made a 24 hour recording of 0 to 25 MHz (7.85TB) and placed six demodulators on the main GMDSS channels on HF between 2 and 16 MHz. You see each channel in a separate window at the top of the screenshot, showing spectrum and spectrogram with time stamps of the recording. Below those six channels you see spectrum and spectrogram of the whole recorded bandwidth, namely 25 MHz. Eventually, below this spectrogram you see 60 x 24 boxes, one for every minute of the 24 hours recording. Just click into the time you want, and the recording instantaneoulsy to it.
Demodulated audio is guided via VAC1 … VAC6 to six different instances of the free YAND GMDSS decoder – see screenshot at the bottom.
There are great many other applications of this revolutionary combination to which I will come back later.
GMDSS-Display reading decoded data streams from seven MultiPSK’s instances in parallel, presenting all information neatly in one database.
GMDSS is a system of ship-coast and coast-ship digital communications on six main HF channels. At an average location in Germany, you will receive about 5000 messages altogether during 24 hours.
In the past, I mostly used the excellent and free YaDD software to decode all channels in parallel (yes, YaDD can be opened in multi instances, each one in a separate folder).
During HFDL monitoring, I came across Mike Simpson’s free software Display Launcher which neatly collects now up to 24 different data streams, coming from up to 24 HFDL channels in a clear database format.
Mike’s software also contains a module called “GMDSS-Display” which now works similar in collecting datastream from up to seven GMDSS data streams, decoded by MultiPSK software.
Yes, also MultiPSK can be opened in many instances, each one in a sperate folder. By this way, it accepts e.g. the audio input of seven different GMDSS channels from an SDR via each different VACs, and decodes each of them.
To do so, the decoded data of each MultiSPK instance has to be backed up regularly:
Configuration -> Regular back-up -> 20 sec
Then, decoded data is automatically written into the appropriate QSO.txt file. This, in turn, is read by GMDSS-Display. Of course you first have to set the paths to guide the software to the appropriate sources.
It takes a bit time of setting it all up, but then you may run this combination until a Windows’ update forces the PC to re-boot 😉
With Mike’s development, you have a unique and mighty tool at hand for a 360° view now also in the field of GMDSS – thank you very much!
Please find below the results of a 24 hours’ session on all seven GMDSS HF channels – coast stations only, automatically drawn onto DX Atlas. All stations received in Germany with SDR FDM-S2 and MD300DX, an active vertical Megadipole of just 2 x 2.5 m of stunning performance.
Received coastal stations on all GMDSS channel/HF during 24 hours in Germany world-wide and …
“HF for the pros is stone-dead, isn’t it?” This rather verdict than question is often heard even by hams. If you are telling them how busy the bands really are (as they cannot read about that in their magazines), they are doubting: “But you need professional equipment plus decoding software, worth my Mercedes Benz?”, they are upset by the answer: “Absolutely bullshit. A software-defined radio at 500 US-$ plus some free software will produce thousands of logs!”
Still don’t believe that? Well, here is the first thousand, caught just in the first half of June, 2016. Received with an FDM-S2 receiver at a quadloop of 20 m of circumference. I mostly concentrated on fixed (rather than: mobile) stations and of modes which can be decoded with free software – if they are not even outright SSB or CW.
You can download this log: Logs_EXCEL from where it may easily be opened not only by EXCEL, but also e.g. free LibreOffice.
If I find time, even more logs from the same HF recordings will be added.
I am greatly indebted to the busy and resourceful friends of UDXF for their work, thanks.
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.]