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.

Decoding the whole DGPS band

Graph1_GPSThis screenshot shows the automatically visualized result of a 12 hours’ session receiving the DGPS band, September 4th/5th, 2016. You clearly see the propagation effect during night.

For years, Chris Smolinski of Black Cat Systems offers a fine selection of Mac software, among them many pieces for hams and shortwave listeners.

He now presented an unique software dubbed Amalgamated DGPS which decodes, analyzes and visualizes all DGPS stations on long wave at once. This is done from an I/Q wav file of e.g. Perseus SDR. DGPS stand for “Differential Global Positioning System” and is a system of long wave transmitters in the range of 283,5 to 324,5 kHz transmitting FSK data in 100 and 200 Baud to correct for GPS signals. Look here for a short introduction to this topic.

These transmitters are of regional coverage, like non-directional beacons, or NDB, in the same band. This makes them interesting for DXing and propagation studies as well.

All you have to do is to let the software analyze your I/Q files of a receiving sessions. Yes, it is automatically “chaining” your files. You then get a detailed list of decoded stations with some additional data. You also can visualize these data, as I did in the screenshot at the top. This is based on a 12 hours’ session resulting in 42 wav files of 675 MB each.

The software runs on both, Mac/iOS and Windows. On both systems it works fine, covering .0 and .5 kHz channels as well as both baud rates.

DGPS_2Here you see the complete list of stations and the number of their receptions. You have to control them a bit to sort out some very few false demodulation like here stations from outside Europe.


PropLab 3.1: How Propagation really works



The software’s unique feature is 3D raytracing, showing an anatomy of propagation (see text).

HF propagation software seems to be full of mysteries. But its all about modeling physics. There are several models around, the most prominent surely is VOACAP, followed by ASAPS. VOACAP comes in very many different tastes like e.g. PropMan 2000 or ACE. It often has been coined to be the “Gold Standard” among hams and professionals as well. VOACAP gives reliable results on a statistical base for a month, whereas ASAPS returns propagation based on the current conditions of a day. It also gives propagation for an aircraft en route during its flight and takes at least a bit care of multi-path propagation which may degrade digital modes. Both work offline as online, and they are fast.

PropLab is giving you a much smarter view on what is really happening on a specific day and time at a specific path or area. It relies on the International Reference Ionosphere (IRI 2007) and uses the ray tracing technique. In short, PropLab is automatically fetching all relevant space weather data (not just sunspots) from scientific sources of the internet to model the ionosphere with its different “layers”.

You then give in your path, antenna etc. in a well-supported way. After having started “ray tracing”, PropLab lets refract rays at exactly this ionosphere with its high granularity and some real-world effect like tilts of layers which will result in e.g. propagation off the great circle. It will also beautifully show effects like focusing and gray line propagation, including Pedersen’s long ranging ray with time resolution up to one second – rather than one hour as that of VOACAP.

This ray tracing can be done in either fast 2D or more time-consuming 3D mode, the latter reflecting both ordinary and extra-ordinary rays plus off-great circle propagation.See the screenshot on top as a 3D example simulating propagation between ALE-station FERB in Far’gona (Fergana)/Uzbekistan and my location in Germany at 16:20 UTC on August 26th, 2016 on 8.066 kHz: elevation of the signal as well as its azimuth had been changed slightly and are drawn into an terrarium-like graphic. Each of the three dimensions has another scale to show all effects as good as possible.  I don’t know any other software (after AREPS went out of the public) which only comes near to modeling propagation like real life. One great advance is that it reveals/shows opportunities of short-living propagation which the other software won’t show. Hence, PropLab is an ideal tool for the serious ham and SWL.

The following screenshots take the above path and its data, comparing the advantage of 3D raytracing over 2D raytracing only on a “footprint” map. The data is rather reduced showing the rays around just one main elevation angle of about 8,5°. If you model the antenna characteristics more realistic, the here empty regions will soon be filled with nice signals. But here I want to show nothing more than a DX example.

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See this slide show changing between signals with and without extra-ordinary rays. The latter easily reach out much wider in the western direction.

Furthermore, 3D raytracing gives with great lucidity nothing more than an anatomy of propagation. This includes e.g. a synthesized oblique ionogram (2D and 3 D), a dispersion chart showing how a signal is spread over time due to different paths and so on. It includes a worldwide terrain profile, taking into account the different quality and angle of reflections on earth (2D).

Even the fast 2D mode reveals many remote chances to receive this station if it had an isotropic (i.e.: non-directional) antenna.

Even the fast 2D mode reveals many remote chances to receive this station if it had an isotropic (i.e.: non-directional) antenna.

I am using this software from its MS-DOS 2’er version, around 20 years ago. It now has arrived at version 3.1, fit for Windows 10. I can absolutely recommend this stunning work of Cary Oler – your shack is not completed without this vital tool. Don’t be scared off by its price tag in times where you expect everything for free: you get an excellent value for your money. And after a while using it you may ask: “How ever can I have lived without it?!”

I will come back on this software sometimes later in more detail. In the meantime, both PropLab2.0 and PropLab3.0 manuals gives an enlightening and free reading.

Audio Log and Google Maps

This is just a first test: I wanted to embed audio logs of some Utility Stations on a Google Map. This is possible only with MP4 files (video) as a link to You Tube. Several kinds of videos are tried: some with HF spectrum and sonogram giving additional information about the signal quality, some with a more static background to optimize file size.

There had been some difficulties to place the spots precisely. It worked fine for e.g. Deutsche Luftwaffe DHM91 (German Air Force) where you see the antennas at satellite view. But it failed a bit for e.g. US Air Force Diego Garcia, where the mark splashed right into the Indian Ocean …

Have fun in clicking to these 15 SSB stations! They should encourage you also to tune into these bands! They had all been received in Northern Germany with ELAD’s FDM-S2 and a quadloop of 20 m circumference.

Critics, suggestions and alternatives to this approach wanted.

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!

Monitoring, State-of-the-Art: In a Nutshell

As I was asked for a look onto my monitoring workbench, I decided to write it down. It’s not to show “the real stone”, but an invitation for discussing efficient workflows which State-of-the-Art technology has to offer.

This PDF of 13 pages contains 25 hopefully instructive illustrations to comprehend my approach to monitoring; or, in this case: Utility DXing. Part of this PDF is also a 2:50 video, showing how to stroll between aero channels and to decode ALE. This video is also placed on top of this page.

The paper explains in detail the advantages of leafing through recorded HF files using the technology of the “living sonogram”. It also discusses some efficient strategies of voice and data reception, eventually touching even documentation.

To make use of the video content, download it on your hard disk, save it and open it by the most recent version of your PDF reader. It works on a PC as well as on a Mac. You can download it here.

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