With the new Elad FDM-S3 and its OCXO/GNSS-stabilized clock, I did a 24h recording of the whole medium wave band on January 19, 2021 in Northern Germany. Free software SDRC V3 enabled me to make up a spectrogram of each channel within a window of 50Hz width, and at a frequency raster of 10kHz. You can easily see:
accurate and stable frequency offset over full 24h down to a millihertz
frequency control of the transmitter’s oscillator (stable, drift, sinus, sawtooth …)
propagational effects (doppler, scatter …)
The format is PDF, DIN-A4, landscape, resolution 300dpi – see screenshot at the bottom. This allows you to zoom to a factor of about 400% to search for details and better read out of the time/frequency scale. It weighs 559MB. You can download it here, and open it with your PDF reader (you can also point your mouse cursor onto the link, click right mouse key, and choose “Save under …”). Leafing from one page to another gives an interesting overview.
Yes, a similar Atlas showing a raster of 9kHz is under way and will be published also here in due time. It is also planned to publish a general article about the background, about what to do with such a tool, and how to do this by yourself.
I am sure that it will open some new horizons on Medium Wave DXing, including accurate offsets over up to 24h.
“Millihertzing” seems to become “le must” of this season. The most recent software stems from smart software author Chris Smolinski, W3HFU, who over many years offers inspiring software,this new one dubbed Carrier Sleuth. It mainly analyzes I/Q-WAV files from software-defined radios at high resolution, being a perfect tool for measuring offset frequencies on mediumave. The screenshot at top shows such a spectrogram which covers 20Hz in width and 24h in length on 590kHz.
Why using “Carrier Sleuth”, when haveing SDRC V3 at hand? First, it works together with a multitude of WAV formats from many different SDR software (see Chris’ list, which is still expanding). Secondly, it let you hop from one channel (9kHz or 10kHz) to the next – if a proper part of the spectrum has already been converted from WAV to FFT. It also provides coverting spectrograms to CSV to apply some statistics on each signal. There are many more smart feature, and Chris will even add some exciting more, e.g. processing I/Q files in real time to save a lot of time.
With my bread-and-butter software being SDRC V3, recording in WAV RF64 one-file format (which sometime swells to nearly 10TB), “Carrier Sleuth” can even digest these recordings with a workaround: specify an interesting part of the medium wave, defined by upper and lower channel and time segment, and convert this into simple WAV. This is easily done with SDRC V3’s Data File Editor. It is also the way, Carrier Sleuth produced the screenshot at top of this page.
Chris published this software first on December 10, 2020. He eagerly looks for bug reports, applications and further suggestions form the users. Take a free test drive; registration code 19.99 US-$.
With Elad’s FDM-S3 SDR now hitting the market, we have a receiver at hand which is supported by an OCXO/ GNSS frequency reference. This combines short-time accuracy with long-time stability and allows for precise frequency measurement in the millihertz range (under 30MHz). Exploiting this feature is as exciting as it is innovative. With this new tool, also a new kind of DXing is evolving. One example is propagation analysis. See below the 24h spectrogram of Radio Gotel from Jabura/Nigeria on its exclusive channel of 917kHz:
What surprises, is both, the late fade out at around 07:30UTC and the early fade-in as early as 15:20UTC. It is important to note that you here see the carrier with a resolution bandwidth of 0.0009Hz, roughly just one millihertz. The gain, compared to a listening bandwidth of 10 kHz, is a whopping 70dB, allowing extreme DX. Audio starts to emerge only from around 18:00UTC. As DX Atlas shows, the whole path between my location and Radio Gotel is under daylight at the palpable fade-in at around 15:20UTC, see screenshot below.
Broadcasting on medium wave still is a very active part of using the electromagnetic spectrum. An unique and outstanding source of information is supplied for free by MWLIST, a team of smart DXers. They provide tons of up-to-date and precise information – down to exact locations and even offsets from the nominal channel.
By visualizing those data, you get an even better insight. Here, free Tableau Public software is (for me) the tool of choice to do just that – please see the screenshot on top of this page. You simply download the free Tableau app, and – also for free – sign up, and you are done.
For me, most striking is visualizing the spatial data, i.e. to show the transmitters at their proper place on a map. Another welcome feature is filtering the data to answer specific questions like: How are traffic broadcast stations above 1.6 MHz spread over Pennsylvania? Or: What can I expect listening on 1521kHz on a late winter afternoon in Europe? Or: Where are Chinese stations located, carrying the CNR1 programme of China National Radio? You will find screenshots illustrating these examples below.
Those are just screenshots, not active maps. If you want active maps, there is an option (WP-TAB, Tableau Public Viz Block) available for WordPress’ business version which I don’t have at hand. But there is a simple solution: go to my Tableau Public page, download my TWBX-map “Medium Wave Station [Copyright MW List]”, and it will automatically be loaded into your Tableau Public app – after you have installed this. Then the map comes into live, and you can do all filtering, zooming etc.
[My profile photo shows a fisher’s deity in Japan, seen in October 2019 in Tokyo’s Kappabashi street. As a DXer and hobby cook, I thought location and statue being quite appropriate – thanks for asking …]
Surely, you immediately will find other ideas to realize, e.g. marking heard/verified signals by just a flag in your list and combining this with a special color on that station on your Tableau map.
P.S.: Taking some suggestions from the fruitful discussion which follows the initial publication of this site, I like to add some more examples:
If you are looking for some challenges, a European listener may start with low-power stations in the UK (LPAM), transmitting with just 1 Watt of power, leaving 500mW from both sidebands, combined, for the audio at max. Filtering the MWLIST with Tableau Public and visualizing this by a map, leads to the screenshot below. I also attached an audio clip of Carillon Radio. Yes, reception quality of this station of the Leicester/Loughborough hospital resembles a bit the state of NHS 😉
A second example is even more challenging for European DXers, but not entirely impossible. The map shows some low-power Japanese service radio stations for parks, traffic, weather and harbours.
Recently, I came across the different sign-on ceremonies of different transmitters. The idea is to understand this workflow in which obviously several stages of the transmitter are switched on consecutively. See at the top one example, where Voice of Turkey is swithcing on their transmitter on 9880kHz in five steps within about three seconds.
The diagram was made with Simon Brown’s unique software SDRC V3. I used the Signals Analyser module, providing a (needed!) time resolution of down to just one millisecond, or 1000 values of level vs. frequency in just one second! These data (CSV) had been exported and visualized in QtiPlot software.
I would like to encourage other people to join these observations. One goal can be toi fingerprint no only a transmitter, but also the workflow of the people at the transmitter. Please refer to this website for a database of broadcasters and their transmitters plus galore of associated data.
In the meantime, I already observed a couple of different workflows/transmitters. Please keep in mind that all these measurements (better: estimations), of course, are prone to fading. You may also see some effects during sign-on in the spectrogram, see below.
In the last weeks, I had used Sporadic-E conditions to stroll a bit in the FM broadcast band in search for DX. Elad’s FDM-S3 covers the whole 20 MHz wide band, and Simon Brown’s SDRC V3 software again provides an unique and most valuable tool to dig out DX. Antenna is an active Dressler ARA-200 (R.I.P.).
This blog entry shows how to make use of short openings of only some (ten) seconds.
First step is to record the whole FM broadcast band for hours on external HD. Then you make up so-called “spectrograms” by V3’s Analyser module. This provides you with a picture of activity (signal strengths color-coded) over time and frequency – see screenshot at top of this blog.
Scrolling through this spectrogram, you can make out even the shortest openings. Just click onto one of them, and the software instantaneously tunes into it. The sensitive RDS decoder of V3 is doing the last step – showing its RDS identification.
The short video below gives one example from a recording of June 26, 2020. On 91.8 MHz, I received semi-local transmitter NDR 1 NDS at Visselhövede (5kW@67 km distance), with “Stand by me”. From the spectrogram, I saw a “blob” (see screenshot at the top of this blog), stretching over around 40 seconds. It turned out to be Algerian’s Akfadou transmitter with Chaine 2 programme, 70 kW ERP@1’810km distance! RDS did tell me. Just have a look at the short video below which was made with V3’s video recorder …
V3 software provides also an a-symmetrical tuning of bandwidth, even at wide FM/BFM. This is important to identify some stations “in the clear” – if they are prone to some spillover from a local/regional station right on an adjacent channel. The following example spots Radio Marca/Mallorca from Spain on 91.6 MHz, suffering not only from a a strong local just 100 kHz below, but also from a very short appearance “out of the blue”, to where it disappeared again after less than 30 seconds. The latter is shown in the spectrogram, made by the Analyser, where I magnified the small/short signal of Radio Marca over 1’541 km. The video at the bottom shows how to evade the interference from the channel below to get the RDS code “B002 R.MARCA” correct.
Sometimes propagtion is too short for any identifcation, neither RDS, nor by announcement. Take the next screenshots as example: The spectrogram shows some very short openings revealing similar pattern which cropping the recording (Crop – > Apply) confirms. It turns out to be an English-speaking stations for a maximum of ten seconds. Parallel listening reveals the same programme on the following eight frequencies: 88.3MHz, 88.4MHz, 88.5MHz, 88,7MHz, 88.9MHz, 89.1MHz, 89.7MHz and 89.8MHz. The only intersection turns out to be Raidió Teilifís Éireann from different locations with their Radio 1 programme.
RTE transmitter usually do have RDS onboard, but here the time with a modest signal was too short to raise the alarm. On the other hand, there are stations with RDS, but not programmed or even without RDS at all. Take Radio Tisnath/Algeria in Tamazight, a Berber language, as an example for the first and Radio Blagovestiye/Russia as an example for the latter:
The news about the death of HF Broadcast are greatly exaggerated. The map on the top presents 574 active stations, scattered all over the world. This interactive map has been made with free Tableau Public software: simply click onto the map, an in another tab of your browser it pops up. Now you can point your mouse to a mark and see some data.
There even is more: as some transmitting sites are used by several broadcasters, this fact is shown by different colors. Your mouse will tell.
The best thing of this map is the fact that it is strictly geo-referenced. If you zoom into a station, you should directly see the transmitting site form above – depending, of course, from the resolution of the underlying OSM satellite map.
After having scrutinzed all sources (HFCC, WRTH …) available, I finally decided for ILGRadio. Only these data are concise, complete and precise – a great achievement of Bernd Friedewald since decades! [To keep things simple, only one transmitter’s power is noted for each site]
This map, together with ILGRadio (see below), works as a promising starting point of future work, e.g. band scans in the light of the 21st century …
IRAN INTERNATIONAL is transmitting in Farsi via their relay station just at the outskrits of Uzbekistan’s capital, Toshkent, with 100kW on 6270kHz from 12:00 to 04:00 UTC, directed towards Iran.
I received this station in winter as in spring. In winter (namely 16DEC2019), the whole transmission from sign-on to sign-off can be received, wheras in spring (namely 02DEC2020) a considerable part of the transmission after sign-on has been lost in the noise, plus the time towards sign-off in the morning largely coinciding with fade-out; though still celarly visible.
You see also a clear greyline enhancement at least on the fade-in. Sunrise and sunsetset for both locations can be seen from the bar chart below in the diagram..
The graphs are based on 2 x 86’400 points each, providing a time resolution of one second. To make things more clearly, the bold blue and yellow lines represent a smoothed version (moving average: 601).
This is just one example of how the actual signal strength of a station differs from season to season. With 24 hours’s recordings of the whole HF on both dates, it is easy to compare also other stations and frequency ranges. If I have time, I will add some more examples in the future.
BTW: I passed the big transmission center southwest of Toshkent left-hand, riding M39 on the way to Samarkand; it was not encouraged to take any photos …
The evening transmission of the Voice of Broad Masses from Asmara-Selae Daro in Eritrea signs on around 14:06 UTC and signing off around 18:30 UTC. Figure 1 shows the signal levels with a resolution of one second, marked by red points, and the smoothed level, yellow line, with a moving average of 601 points, or 10 ten minutes. Smoothed levels span a range from -106 dBm/Hz to -80 dBm/Hz.
There occur considerable peaks around 14:30 UTC, 16:15 UTC and 17:30 UTC. Raytracing the signal, transmitted by a Quadrant antenna HQ1/.25, will help to reveal some mechanics behind the curve.
Figure 2 shows a four-hop propagation via F1 layer at 140-160km with a relative steep elevation of about 22°. The much shorter hops, reflected at the E-layer at a height of about 100km, are of less to no importance. The signal gets through, but very weak. The path itself still is in full sunshine, see Figure 3.
There is a very short, but distinctive peak at 14:30 UTC. This coincides with a similar short time of three-hop propagation (Figure 4) from a very low azimuth of 3°. Of course, the full path still is in daylight.
Just after 16:30 UTC and near sunset at the transmitter (16:37 UTC), there is reached the bottom of kind of a “Hillary Step” before the last run to the peak. The way to a (quite short) plateau starts around 17:00 UTC. There we have a textbook-like two-hop propagation (Figure 5) with the greyline covering just more than half of the great circle path (Figure 6). There, an elevation of under 5° is needed.
Propagation on HF differs from day to day. The nine diagrams at the top show the signal strengths of China Radio International’s Kashi transmitter, 500 kW, beaming to Romania; 08:58 UTC to 09:58 UTC from March 15 to March 23. The basic resolution (black grey points in the background) is 100 milliseconds, whereas the blue line marks the moving average with 601 points. The “moving average” can be best understood as a lowpass filter, revealing possible trends on a coarser scale. In this case, you cannot see such a trend.
If you compare a part of each transmission on a much finer scale, you even see sheer chaos, as the Figure below is showing:
There seems to be no visible correlation on any scale in this case. There are other cases where, however, some correlation can be found – to which I will come back in some future entries.
The last diagram at the bottom of this pages shows a much more forgiving picture of the signal: the average level changes not more than ±4 dB between best and worst days. This so-called box diagram illustrates best the actual receiving quality of the broadcast, demodulated with an synchronous detector to largely avoid severe distortion by selective fading. The difference of deciles 90% and 10% marks the fading range, a key figure in describing the quality of reception – see “Ionospheric Radio” by Kenneth Davies [London, 1990/96, pp. 232].
Analyzing signal strenghts, is an interesting tool to get to know more about propagation. I will continue this topic – stay tuned!