Tag Archives: Broadcast

Offset/SNR: Some Ideas for Medium Wave DXing

Offset_5

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: Ex oriente DX

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.

BEL3_Fishery_FRS_1143kHz

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

Read more

2,5+ million of Field Strength Data from ITU

Tehran-Norddeich_1983-1989_15K1MHz_3D1

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.

Kp_vs-Flux_2

Solar flux (F10,7) vs. geomagnetic activity (Kp index), 1969-1993.

 

SDR Console V3: Signal History and six RX Panes!

KPL

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]

iZotope RX6 – A Miracle in restoring Audio

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:

CKZN_1

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:

CKZN_6_2

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:

CKZN_6_denoise

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!

 

20 MHz HF: “HackRF One” on Shortwave

world Kopie

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.]

Multi-Channel Monitoring

Matrix_24_RDS

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)
  • … and much more
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