Category Archives: Propagation

Play it again, HAARP

Alaskan station HAARP is re-activated for some scientific purposes in late February, 2017. I received them on 2.800 kHz as well as on 3.300 kHz with carriers showing their scheduled pattern. Alas, reception was too weak to make out any modulation. See screenshots below, containing all sufficient data like time, frequency, resolution etc. Reception has been done in Northern Germany with FDM-S2 by ELAD at a quadloop antenna of 20 m circumference.

Decoding the whole DGPS band

This screenshot shows the automatically visualized result of a 15 hours’ session receiving the DGPS band, March 11th/12th, 2017. You clearly see the propagation effect during night (marked yellow).

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.

[Einen deutschsprachigen Test der aktualisierten Software habe ich in der April- Ausgabe 2017 der Fachzeitschrift FUNKAMATEUR veröffentlicht.]

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 15 hours’ session resulting in 56 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.

Here you see the complete list of stations and the number of their receptions. “Amalgamated DGPS” has decoded 516.918 logs in roughly 15 hours!


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.

[Einen ausführlichen deutschsprachigen Test mit vielen Screenshots und Beispielen habe ich in der Januar- Ausgabe 2017 der Fachzeitschrift FUNKAMATEUR veröffentlicht.]

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.

Read more

ASAPS: HF Prediction online & free!

Flight AF 128 from Paris to Beijing: What is they best time/frequency combination to communicate with Stockholm AOCC on HF?

Flight AF 128 from Paris to Beijing: What is the best time/frequency combination to communicate with Stockholm AOCC on HF en route?


HF prediction seems to be a somewhat neglected field among short wave listeners, as well as hams. At the same time, some knowledge of how propagation works on specific paths or into defined areas will greatly enhance your hunting success. If you have considered the somewhat flat learning curve of some software as an obstacle, there now is no excuse. With ASAPS’ recently even more improved online services, you are on the sunny side of HF right now.

I had written a short paper explaining how this free service can be used especially for Utility DXing. If you also ever wanted to know the relation of a waste paper basket and multi path propagation, please download this PDF (7 pages, 22 illustrations) here.

Perseus & Markers: Great Tools for analyzing Propagation!


The Perseus SDR comes with a software, where you may define up to eight markers. Each of them measures the level of the signal at distances of 100 ms to 5 seconds and writes it into a CSV file. This is the base for further analyzing these data, i.e. propagation. See such an analysis of the fade-out of CHU on 3.330 kHz on top of this page.

With an (active) antenna delivering a constant antenna factor over specific range – as all professional antennas do, e.g. RF-Systems’s DX-1 – you may also switch to logging the field strength of the signal in dBµV, rather than the input level in dBm.

The first paper presents a general introduction into this concept. It has been translated into English by Guy Atkins.

The second paper, in German, goes more into the depth of analyzing the data. But it’s 13 illustrations will make it under stable also to readers who don’t understand German.

Five Mongolians on Long wave


Since I visited Mongolia in 2001, I fell in love with this country. Hence, reception of all their radio stations on long wave caught my double interest. With some help of other listeners, I managed to receive all stations and analyzed their reception. Without any 100 g of Chinggis Khan Vodka, to which I surprisingly bumped into at Sarazul at Warnemünde in late summer 2015 …

Read this paper, to get also some information on how to receive and analyze stations which even might be too weak to hear.

Solar Eclipse 2015: Some signals did improve, some didn’t


The Solar Eclipse on March 20th, 2015, provided some unique Monitoring opportunities in Europe. It was the first time that broad parts of the spectrum could have been recorded and analyzed even by hams.

I recorded the range from 0 to 2 MHz to analyze the effects of the eclipse on different frequencies: on VLF signals dropped significantly (see the W-shape level of DHO38 on 23,4 kHz above), whereas on medium wave signals did improve.

This paper covers my observations in e.g. 29 illustrations and some audio files.

Caveat: Embedded multimedia content will only work with the most recent version of Adobe`s Acrobat Reader. And you have to save the PDF on your device (hard disk/stick), to make use of these multi-media.

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