With some iteration, as described in the PDF, the former unknown site of a CIS-12 transmission on 6.465 kHz has been disclosed as the Russian Navy from Baltysk, Kaliningrad.
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.
“Living Sonagram”: On the right window, you see a part of a 24 h recording at 6,1 MHz bandwidth (ca. 2 TB) with 1 line/second. Tagged is the sign on of Dimtsi Hafash which is received by the undocked “Receive” panel of V3’s GUI. At the bottom: signal strength on 7180 kHz over 24 hours reveals e.g. s/on, s/off and fade in.
Just a small note on a real real big event: Simon Brown, G4ELI, has published V3 of his indispensable SDR Console software on June 18th, 2018 – after three and a half years of heavy coding. Download it here and donate. Or vice versa.
V3 is a quite universal software for most SDRs on the market. For all, it provides the same graphical user interface (GUI) and the same functions (plus those specific to some devices).
DXer’s delight: On top the sonagram to visually catch signals (here: JDG from Diego Garcia; tagged). Bottom, from left to right: receive GUI for fine tuning, decoder W-Code showing “JDG”, below this “Playback” panel for controlling the recording (back/forward, e.g.), and on the right a database.
There are many unique functions and modules which will take DXing with SDRs to the next step. For now, let me mention just two of them:
24 parallel demodulators within the SDR’s bandwidth – fully independent in e.g. mode, bandwidth and AGC to receive, record and decode 24 signals/channels in parallel.
a sophisticated File Analyser which presents a recorded band as “living sonagram” – whre you see and click to a signal which then is played via the basic GUI
Up to six parallel demodulators can be seen on the main screen (from up to 24 possible).
1520 kHz from 18:00 to 05:00 UTC (local SR/SS: 19:43/02:58 UTC) with 100 Hz bandwidth and 0,0031 Hz resolution (= +65 dB over 10 kHz!) reveals at least 27 stations and their offsets.
Each of these just two features mentioned will open new worlds for DXing and even serious professional monitoring. I will be happy to come back to some applications of V3 in more detail.
Thank you very much, Simon, for providing this excellent tool for free!
4’800 kHz: First CNR1 with sign on at 20:15 UTC and fade out, then AIR Hyderabad with the same, but s/on around 00:06 UTC.
You may export levels over time on one frequency or level over frequencies at a given time. This graph visualizes the activity on 7435 kHz with 86’400 levels (on per second over 24 h). The data had been exported to QtiPlot for further investigation.
Offset-DXing “on the fly” shows four different stations (spectrogram) on one nominal channel, namely 801 kHz. The window is baout 30 Hz wide and shows the carrier on HF level.
Although I use Simon Brown’s excellent software SDR Console V3 for years, I only now discovered a feature, being most valuable for medium wave DX.
Nearly each medium wave channel is populated by a couple of stations which mostly have a slight difference from each other, called offset. This often is specific to specific stations. It even reveals stations too weak to be heard. Software V3 will show these carriers of HF level during normal listening, being live or from an HF recording.
Read MW-Notes, to get some information on “how-to” on 6 pages, with 12 screenshots. There you will find also a hint for a method with even much more resolution (but: not “on the fly”) plus some information on how to measure signal strength and estimate/calculate the SNR of speech/music, rather than that of just the carrier.
You have to distinguish between absolute and relative frequency accuracy; the first is best achieved with a GPS-disciplined oscillator, the letter the normal case.
P.S. I started with these things back in 1997 with an evaluation board from Motorola, followed by sound card & software on audio level (“Soundtechnology zeigt Signale: Sieh’, wie es klingt!”, funk magazine 6/1998), to be continued on HF level from 2006, first with RFSpace’s groundbreaking SDR-14. Three years later, I published a survey of each and every 9- and 10-kHz-channel on medium wave by this method. After Apple closed their web service, these pages had gone astray, and the information is now not up-to-date anymore. State-of-the-Art now is the method described in the paper.
Medium wave saison has started, and am I trying to make the best out of it. Conditions are fascinating different from day to day, and even from minute to minute. With mainly focusing on “East of Suez”, with some other in between, please find some 50+ audio logs below. Click “Read More” button at the end, to expand the list to full length.
I am very much indebted to Christoph, OE2CRM, who with his very special mixture of charme and nuisance more or less forced me to explore a bit more of this frequency range 😉 First of all, I was and still am attracted by his outstanding logs which had been held impossible in Mid-Europe in the last decades.
I am using an Elad FDM-S2 at a wire loop of 20 m circumference with Wellbrook’s Large Aperture Loop Amplifier ALA100LN plus 7th order elliptic low-pass filter (1,5 MHz) by Heros to avoid any spilling over from HF (mainly that of: Radio Romania International); software used V3 from Simon Brown.
Part of the QSL from “Fishery Radio Station” (Taiwan Chü Yuyeh Kuangpo Tientai), BEL3, 100 kW, 1143 kHz, received September 25, 2017, 19:00 UTC. 謝謝, Station Manager Jin Mey Ju!
1700 kHz USA-Florida WJCC Radio Mega in French, Miami Springs, 10 kW, 10-OCT-2017, 02:00 UTC. Several IDs (e.g. in French) of this multi-cultural broadcaster.
1584 kHz G Punjab Radio, in Hindi/English, London, 2 kW, 15-AUG-2017, 20:00 UTC. ID.
1566 kHz KOR HLAZ FEBC in Korean, Jeju, 250 kW, 26-SEP-2017, 17:00 UTC
1566 kHz HOL Vahon Hindustani Radio in Hindi, Den Haag, 1 kW, 23-AUG-2017, 22:00 UTC. ID in Hindi.
1557 kHz TWN RTI iLoveMusic in Chinese, Kouhu, 300 kW, 20-SEP-2017, 16:55 UTC.
1550 kHz ALG Saharawi Arab Democratic Republic National Radio in Arabic, Tindouf, 50 kW, 27-SEP-2017, 21:01 UTC. ID: “RASD punto [?] info …” & in Arabic
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!