Seven years of hourly field strength data of a transmitter in Tehran/Iran, received at Norddeich/Northern Germany. You clearly see the influence of time, day, season and solar activity.
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!
The diagram at the top has been made with QtiPlot software. The same software has been used to visualize solar and geomagnetic WDC data, obtained from GFZ Potsdam – see diagram at the bottom.
Solar flux (F10,7) vs. geomagnetic activity (Kp index), 1969-1993.
NEW: The Receivers’ Pane on top covers spectrum and spectrogram of up to six demodulators – look at different modes and bandwidths. Also new: “Signal History” at the bottom.
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:
With some statistics applied on the CSV file of Signal History, you’ll get a deep inisght into fading structures. Top: original data (black), averaged (yellow), median (read line). Bottom: box diagram, histogram, 3D-band. See following screenshots for some examples.
… and this is just the beginning! [Receiver: Elad FDM-S2 & AirSpy with SpyVerter]
If you still desparately looking for a software to restore your recorded DX audio clips, iZotope’s RX6 offers an alomost perfect solution. While the de-crackling tool automatically removes all of these annoying statics, the near-unbelievable tool “Spectral de-noise” is doing wonders in extracting e.g. formants of speech out of noise, thus greatly enhancing intelligibility.
I did a convincing test with a clip of CKZN, New Foundland’s shortwave station still transmitting on 6.170 kHz with 1 kW; received June 1st, 2017 at around 02:00 UTC. The original recording is heard like this:
It looks like this, when opened in RX6, with spectrogram in the background:
First step was to automatically get rid of most of the static by “de-crackling”. RX6 offers you the chance to see also the garbage, e.g. what has been subtracted from the signal, see screenshot below with a focus on the identified crackles:
After this first step, the audio sounds like this:
Second step is the tool “Spectral D-noise”. Most comfortable is the “adpative mode”, where you see the audio much more clearly than in the original recording:
And that’s the way, it sounds, with 12 dB attenuation of noise (default):
Another mode is the “learning mode”, where you teach the software what it has to consider as noise in the recording, and then clean it up. First, I did it with the strongest value of 40 dB reduction:
Sounds quite artifical – but drop your ear onto the last part, how clean the jingle sounds!
With some right, default is 12 dB, listen here:
This may be reduced to even 6 dB – you have to find the right balance by yourself:
To restore audio of DX MP3 clips, is not where this software is really adressed to. But even for this purpose, it’s strong algorithms perform better than any other device/software, I’ve seen in the last 50 years. And there are a lot more functions to tweak a signal further. Not really cheap, but unique. There’s simply nothing better!
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.]
In recent posts, I already wrote about my experiences with Simon Brown’s software SDR Console V3.0. It matches most SDRs, delivers now up to 24 virtual receivers and is capable to run multi instances, i.e. you may run several SDRs on one PC in parallel.
That’s exactly what I did when I connected three SDRs FDM-S2 to a PC, running 35 different ARINC-635 channels in parallel resulting in 68.000 decoded messages. It worked brillantly.
And there is much more, e.g. recording and playing 24 audio channels from broadcasters throughout 20 MHz (the whole FM band!) with hardware RFHack One.
This paper provides a hands-on and step-by-step guide for some vital monitoring tasks like:
using up to three receivers on one antenna and one PC
working with multi instances of GUIs
working with multi instances of software decoders like PC-HFDL and MultiPSK
carefully planning a monitoring session
analyzing the decoded results and apply some basic statistics on 68.000+ messages
record and play 24 channels incl. RDS data within a bandwidth of 20 MHz on the FM broadcast band plus on HF with RFHack One (see screenshot on top of this page, “Matrix” mode)
The original software for Elad receivers provides a very useful feature, resembling the old radio scale: it inserts some station data from a list on their proper place in the spectrum – see screenshots above (utility) and below (broadcast).
You may invoke several lists like EiBi and your own memories. These list just must comply to the data standard, Elad had set. You may also set up your own list. If you sepcify a transmission time other than 0000-2400, only the stations active at this time will pop up.
With Bernd Friedewald’s (DK9FI) International Listening Guide there is such as matching list available providing 31.000+ entries of brodcast as well as of utility stations. Bernd is a long-time professional in the field of broadcast monitoring and international consulting in this field. You may also edit this list.
(Disclaimer: I have no commercial relationship with ILG, and bought the data like everyone.)
Nach wie vor sprechen internationale Rundfunksender noch mit einer starken Stimme auf Kurzwelle. Diese Einführung beschreibt auf 33 Seiten und mit 31 instruktiven Abbildungen sowie vielen integrierten Hörbeispielen, wie diese Kommunikation zwischen Sender und Hörer funktioniert. Anders als sonst, wird hier auch die Planung aufseiten der Sender berücksichtigt – und was wir Hörer davon haben.
Schon das opulente Cover (siehe oben; Dank an Christoph Ratzer, OE2CRM!) zeigt, dass in diesem Thema weiterhin jede Menge Musik steckt!
This 33-pager in German has been written as introduction into international broadcasting on shortwave. It covers frequency planning of the transmitters as well many aspects for us listeners. 31 illustrations and many sound example may make it digestible even for people who don’t speak German.