Just after the spring equinox, interdisciplinary artist Amanda Dawn Christie did another performance of her ionospheric transmission art project “Ghosts in the Air Glow” via the High Frequency Active Auroral Project HAARP near Gakona/Alaska. I took an HF recording of a range, covering all frequencies and times scheduled – see here. At my location, on March 26th, 2019, reception was possible only on 5.100 kHz (best), 6.900 kHz, 7.900 kHz and 8.000 kHz. Signal strength was too low to hear any modulation, but the characteristics of the signals did exactly match the schedule – see screenshots and captions below.
Category Archives: Propagation
The stunning direction finding tool on the KiwiSDR net has hit the community. Most people are enthusiastic about the new horizons, some some smart people had opened for free.
A few people, however, reported some disappointment as they couldn’t pinpoint each and every transmitter with expected high precision.
To avoid this disappointment, you have to know what you are doing. The TDoA tool for direction finding indeed delivers automatically stunning results. But you have to think a bit about the setup, and also do some iteration.
I wrapped up my first experiences with TDoA in this PDF. You may simply download it by double-clicking the link, and open it in a PDF reader. It consists of 22 pages and 37 instructive figures. I greatly stressed the practical part of direction finding with this tool – with 13 explicit case studies from 2,6 MHz to 15,6 MHz.
The idea is to have more fun by getting the most reliable results.
Undoubtly, a Graves is a fine French wine from the Bordeaux region in western France. So it is so surprise that also GRAVES is an extraordinary Radar station. It was built to detect and follow satellites and their debris. They sequentially cover from 90° to 270° azimut in five big sectors A to D, and change from sector to sector each 19,2 seconds. Each of this sector is further divided into 6 segments of 7,5° width, covered for 3,2 seconds each.
They are transmitting on 143,050 MHz. If you are in Europe and tune into 143.049,0 kHz USB, you probably will hear/see some reflections of meteors, airplanes and even spacecraft. The distance between the transmitter and my location is about 630 km, and for their southly directed transmissions, there most of the time is no direct reception.
So, if you tune into 143.049,0 kHz, you will see just a blue spectrogram: noise. If you wait for a while, some signals will appear out of this blue; see screenshot on the top. With Simon Brown’s free software Version 3 you may also take a level diagram in smallest time steps of just 50 milliseconds:
This level diagram shows the big advantage of SDRs, working on the signals on HF level, rather than of audio level as with legacy radios. The latter additionally introduce e.g. noise and phase errors. Of course, you may also listen to this signal:
From this audio, in turn, you may do an audio spectrogram, possibly revealing further details of e.g. of the trilling sound like that from a ricocheting bullet: The Searchers (the 1956’er Western film by John Ford, not the British boy group from 1960 …) on VHF.
P.S. If you want to donate: my favourite Graves is from Domaine de Chevalier, blanc …
The International Telecommunications Union recently published many information for free, which had been locked for years behind an often impressive cash house or had been available just for a few blessed.
Among these information is a bonanza of 2,5+ million of normalized field strength data from the years 1969 to 1993. This time covers two solar cycles and by far doesn’t provide insights of only historical interest: You e.g. may visualize some circuits to see the influence of day, time and solar activity at a glance. And you may use this data to analyze some dependence between field strength and solar/geomagnetic activity.
As these data so far hasn’t attracted any interest of ham radio magazines, we are just at the beginning to make use of it. Join in!
Simon Brown, G4ELI, has further developed his software SDR Console which has become THE platform for a real bunch of very different SDRs. The new public preview has two more exciting features:
- “Signal History” takes the signal strength of the given bandwidth each 50 milliseconds, which can be saved in a CSV file. It is also shown in three different speeds on a display.
- “Receivers’ Pane” shows up to six combos of spectrum/spectrogram of the complete up to 24 parallel demodulators (they additionally can be shown in the Matrix, as in former versions).
See screenshot on at the top.
“Signal History” offers many applications, to name just three:
- analyze fading and its structure with an unsurpassed time resolution of 50 ms
- document fade-in and fade out
- measure signal-to-noise ratio of signals
As an First Aid, I have written a PDF of 19 pages with 36 instructive Figures. There you find a step-by-step introduction plus numerous example on how to use this valuable tool in practice. Please download it here. (Another tab opens, where you have to double-click “SDR_COM_Marker” to start download.)
Surely, I will come back to these most welcomed features in more detail. For now only some screenshot examples regarding “Signal History”, which have been realized by analyzing the CSV files with QtiPlot:
… and this is just the beginning! [Receiver: Elad FDM-S2 & AirSpy with SpyVerter]
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.
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.