Category Archives: Propagation

DAB: Unique Software Qirx for SDR – smart, Feature-rich and free (2/2)

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In this second part about DAB/QIRX, I will deal with anaylzing some results of QIRX’ log.

Figure 1: Tag cloud of all DAB ensembles, revealed by a 24h scan of the whole DAB frequency range at DK8OK’s location near Hannover/Norther Germany. The bigger, the better.

QIRX software provides several tools and data for DAB reception which it stores in a file called TII logger. TII stands for Transmitter Identification Information. Most important of these data are:

  • Time of reception
  • Ensemble ID – identification of the DAB-VHF channel received
  • Signal-to-Noise ratio, or SNR, of the whole 1.536MHz wide VHF channel. Maximum values here are about 34dB from locals. Audio can be expected from about 9dB, reliable decoding of metadata from around 7dB
  • Main ID and Sub ID of the physical transmitter’s location
  • Strength – the average of the amplitudes (magnitudes) of the TII carriers of each transmitter at that moment. The strongest carrier within an ensemble gets value “1”, the other carriers a number from 0 to 1 in respect to their relative magnitude, compared to the strongest carrier. Scale is linear, not logarithmic.

For mobile use, also GPS data in 3D are stored, extracted from an NMEA stream, provided by e.g., an external GPS mouse.

There are two principal methods of collecting data:

  • Scanning the whole DAB-band with all ensembles or scanning a couple of ensembles, as set in the Options’ tab, see Figure 2. This is done to get an overlook over all or many ensembles.
  • Scanning of just one ensemble, mostly to scrutinize propagation from the physical transmitter’s locations – Figure 3.

For scanning, the position of the Threshold slider is important. This can be considered as “kind of a squelch”. It sets the threshold where an ensemble/service is logged. You can control this feature via the window “TII Carriers”. A high threshold results in reliably logging of the strongest station(s). A low threshold will save also weak(er) signals but may be prone to false positive logs which have to been checked/erased manually.

Figure 2: Scanning the whole DAB band or just some ensemble(s). The results are automatically written into the TII logfile – here opened, in the background.
Figure 3: Scanning just one ensemble, here 5D. Under the TII tab, your first must start TII Recording for logging. After that, you may access this file by double-clicking the page icon at the right of this row.

Scan the whole Band

A scan of the whole band with a high threshold (here 0.54) resulted in the ensembles of Figure 1. Reception has been done from a fixed location with a largely vertical-polarized discone antenna at a height of about 50m near Hannover, in the lowlands of Northern Germany. The radio horizon is about 30km, following the equation given by Armbrüster/Grünberger: Elektromagnetische Wellen im Hochfrequenzbereich, München/Heidelberg [Siemens], 1978, p.48. Their factor of 4.1 is a bit higher than other values also found, ranging around 3.6. Receiver is an SDRPlay RSP2.

Figure 4 shows the SNRs of three ensembles, transmitted by the local Telemax tower at 15.8km with antennas at a maximum height of about 340m above sea level, or ASL. This results in a radio horizon of 75km.

Both 10kW signals of ensemble 5C and 5D show a more or less similar SNRs, but at different medians of 27.0dB [ensemble 5C], 31.3dB [5D] and 27.1dB [7A], respectively. With (nearly) the same power and the same horizontal polarization – matching my vertical Discone antenna -, with 5D leading the pack by a whopping 4dB, or factor 2.5, presumably using another antenna pattern at the transmitters’ site. What puzzles me more is that the variance of ensemble 7A with 1.56 is more then double as high as with the other signal (0.62 and 0.70).

Figure 4: Three ensembles from the local transmitter deliver different SNRs, see text.

The next diagram (Figure 5) shows the SNR from ensemble 11C, transmitted from Brocken mountain. With a height of 1141m, it is also virtually line-of-sight. There we see a much lower SNR, due to the fivefold distance, plus the transmitter’s power of being only a fourth that of Hannover Telemax. With 10.2dB, the median SNR is barely above the reliable threshold of around 10dB to provide audio at all. Showing a variance of 0.9, it is prone to sink under this vital level – returning no audio then. The three bigger dips largely coincide with local sunrise, noon and sunset. Further studies are needed to get a clue on that.

Figure 5: The SNR from ensemble 11C, as transmitted via the Brocken mountain, sometimes drops under the vital threshold of 10dB; see text.

The last diagram of this series, Figure 6, shows a splash of DX: From my location, the transmitter “Eggegebirge/Lichtenauer Kreuz” only provides marginal reception – with a median SNR of 8.6dB and a variance of 0.3 only rarely jumping over the threshold of 10dB. Sometimes, even metadata are lost, resulting in a somewhat thinned-out appearance of the diagram.
If you compare the diagrams from Brocken above and from Eggegebirge below, you may see some similarity in SNR over time with also pronounced dips around sunrise, noon and sunset.

Figure 6: Only marginal reception is provided by ensemble 11D, Radio fuer NRW, from Eggegebirge. It rarely jumps over an SNR of 10dB which is needed for audio.

Scanning one Ensemble

In a second step, I scanned just one ensemble for 24 hours, namely 9B “NDR NDS LG” on 204.640MHz with a choice of six stations – some easy, but e.g. Stade a bit challenging. Figure 7 shows the locations and some results, from a whopping number of 276’092 logs. For this, “Threshold” had been set to the lowest possible value, combining highest sensitivity with a maximum of false hits (here: nearly 30%) to be sorted out later – which of course had been already done in this example.

Figure 7: Visselhövede transmitter provided continuous reception with nearly 80’000 hit counts when having scanned ensemble 9B for24 hours. From this diagram you see the relation of hits, distance and transmitting power of all received six locations.

To get the performance of each transmitter’s locations within one ensemble, you cannot use the SNR values, as they refer to the strongest station within the ensemble: Visselhövede in this case. Hence, I had to use column “Strength” of the TII log, running from “1” for the biggest signal in the ensemble to “0” on a linear scale. Here, the smart guys of UKW/TV Arbeitskreis e.V. have invested much work in identifying the TIIs. If you match the Main/Sub Id of your TII log with their free publications, you can assign the IDs to their locations.

This has been done for Figure 8, sorted by distances of the transmitters. The Bispingen/Egestorf (74.2km) transmitter is running only 2kW, hence its strength is weaker and more patchy than e.g. 10kW transmitter Dannenberg/Zernien, despite its distance of 91.2km. Most prominent in the diagram of this transmitter, you see two peaks between 18:00 and 00:00 UTC. They occur – each time-shifted and weaker – also in the diagrams from Egestorf, Lüneburg and Rosengarten plus, much weaker, Visselhövede. Source of these peaks almost surely is a “moving reflector”, being more an airplane than an atmospheric phenomenon, enhancing reception currently. Websites like Flightradar24 with their playback function will help to find some suspects.

Figure 8: Strength of all six transmitters, observed at ensemble 9B over 24 hours. Please observe each different linear scale!

Finally, an alternative look at strengths. In Figure 9, I combined the strengths of just three transmitters, now having set a logarithmic vertical scale, rather than a linear scale to emphasize the weaker signals.

Figure 9: Signal strength of three transmitters from ensemble 9B, compared over 24 hours at a logarithmic scale. Compare this view to the linear diagram above to see here a much better resolution of weak signal strengths.

Some Notes on Propagation

Last but no least, I like to add some notes on propagation. In the DAB frequency range, of around 170 to 255 MHz, propagation largely follows “line of sight”, primarily controlled by the height of transmitters’s and receiver’s antenna – plus power of the transmitter and sensitivity of the receiver. Antenna polarization also plays a role – the polarization of the receiver’s antenna must match that of the transmitter’s antenna to avoid losses by a mismatch. Bear in mind that many transmitter’s antennas may have a non-omni-directional diagram.

This general propagation can be enhanced or degraded by atmospheric phenomenons, high or low pressure/temperature; by rain and fog, by aircraft scatter and other factors.

The SNR of an ensemble is mostly as better as the signal is stronger. There is an exception: if the same ensemble is received by two transmitters at a relative distance of more than about 75km, the “Guard Interval” is too short to sort them out. Result then is a reduced SNR at a high signal level. However, I never faced this situation.

Clem dropped my attention also to another most valuable tool, provided by fmscan.org. They maintain detailed databases also on DAB transmitters, their antennas, powers, ensembles etc., and a web service which will draw circles of coverage onto a map. This is a cool and free tool, you must not miss – see Figure 10.

Figure 10: A web service of fmscan.org provides a tool for drawing the coverage (“footprint”) of specified stations, locations, frequencies etc. onto a map. This has been done here for ensemble 9B of six transmitters. Receiver “Burgdorf” can be found som 20km north-east of Hannover, at the bottom of the maß in the middle. Coverage from Dannenberg/Zernien had been highlighted.

The above mentioned tool does not take into account topographic data which may be important to calculate the coverage in mountainous regions. Here Nautel, a Canadian producer of transmitters, provides a free webtool after registration, see Figure 11.

Fgiure 11: Radio Coverage of DAB transmitter “Brocken”, taking into account terrain data.

HF: Doppler, Signal Level and Time

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Two views of the carrier of Sofia-Kostinbrod on 9400kHz from 15:30 to 18:30 UTC: On top the frequency within a window of 2Hz height only, at the bottom the synchronized HF level of this carrier; see text. [Click onto the picture for a better view.]

What you see in the picture at the top, is a mostly hidden gem of HF propagation. I took the carrier of Sofia-Kostinbrod transmitter form Bulgaria (250kW) on 9400kHz and observed it for three hours. In the upper window you see the frequency wihtin a window of 2Hz height only. You see two strong carriers: one nearly in parallel to the x-axis, the other snaking some fraction of one Hertz below it.

With one transmitter only on this frequency: How does this happen?

It’s multipath propagation. The signal takes one way via a groundwave-like way, the upper trace. It reveals a very slight drift downwards. As I use a GNSS-controlled receiver, the FDM-S3 from Elad, this miniscule drift should be happen within the transmitter, not the receiver.
The snaking trace stems from a second way, most likely via the F2 layer of the ionosphere. As the ionosphere is prone to winds and an ever dynamic change of its ionization, it is moving. And with all moving objects, also this causes a Doppler effect to waves. This is exactly what we see – the angular speed of the ionosphere, relative to the “groundwave-like” signal.
You may also see at least two weaker traces, caused by two further ways, hence showing other Doppler shift.

In the diagram at the bottom, you see the combined level of all traces. Because they reach the reeiver at different time and, hence, different phases, their addition leads to an ever changing signal level, called: fading.

I hope to continue this work with some other examples in the future, also taking fade-in and fade-out into account.

Doppler: Following Airplanes’ tracks

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Carrier and Doppler trace (left), locations of transmitter, receiver and track of flight NH8406 – March 27, 2021, around 16:45 UTC [click onto the screenshot for richer detail]

Working on a project which will focus on Doppler spread of HF channels (see at the bottom) and other impairements, I also bumped into some more prominent Doppler catches, namely on the VHF aero band. I took the AM carrier of nearby Hannover VOLMET on 127.4 MHz and observed doppler traces about plus/minus 200Hz the carrier frequency. Following the acitvity in the airspace via Flightradar24 in parallel, it is easy to match traces and aircrafts. In this case, I nailed cargo flight NH8406 from Frankfurt to Narita/Tokyo. It is important to remember what is shown in left part of the screenshot: it is the signal of Hannover VOLMET, reflected by this moving Boeing 777-F. Thus, the reflected frequency shows a Doppler frequency shift – depending on the relative speed in respect to transmitter and receiver. A positive Doppler frequency signals that the aircraft is approaching my location. When it turns to the lower frequencies, I see the aircraft passing.

Things get more complex wen it comes to the Doppler shift at HF propagation. You will also see planes, but effects from high winds in the upper atmosphere, coming and fading of ionospheric layers and the influences of the geomagnetic field are prevailing. Due to the much lower frequencies, the effects are just about a tenth compared to thie above example on VHF.

See below a result from my observations on HF as a preview.

Carrier of TRT Emirler, Turkey, in the 19 meter band. Just after sunrise, the carrier splits into two, and you also see double lines due to magnetoionic effects. The window shos about 3Hz in the vertical, and about 40 minutes in the horizontal scale.

Propagation and MUF: Some notes

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Solar Cycle #24: The Maximum usable frequency (MUF) largely follows the solar cycle. But even during not so active periods, it mostly reaches at least 20MHz. Data from Ionosonde Juliusruh of Leibniz-Institut für Atmosphärenphysik e.V. an der Universität Rostock.

We all know that propagation largely follows solar activity – on a diurnal scale, as well as along the seasons and, above all, the solar cycle – see diagram at the top of the page. We just had entered solar cylce #25, and again some unchartered waters, filled with high hopes as well as some shallows. This is a good opportunity to have a look into the rear view mirror, as in general terms we can see part of the future in the past.

To do so, I did some explorative data analysis, available for free from the following sources:

The following diagram shows the correlation of the daily sunspot number with the maximum, the mean, and the minimum MUF as measured that specific day. Therefrom, you see a decent correlation between solar activity and the MUFmean, whereas the impact of solar activity onto the MUFmax splits up at sunspot numbers above ca. 125. Values above in some cases do enhance the MUFmax, and in some cases just to the opposite. The good news, however, is that even at low solar activity, there may be experienced a MUFmax well above 30MHz, the threshold from HF to VHF.

Daily sunspsots vs. daily MUFmax (red), MUFmean (blue) and MUFmin (grey) at Juliusruh.

One of the reasons that “more isn’t more in each case” lays geomagnetic activity, also triggered by the sun. From the data trove, I took seven days of November 2012: A stream of days with good propagation is interrupted by one day where the MUFmax in knocked down from more than 30MHz to just under 15MHz. The reason is a coronal mass ejection (CME), resulting in a magnetic storm, disturbing the earth’s magnetic field and, hence, ionospheric propagation. Already on the next day, propagation is recovering. Please have also a look at the “silence before the storm”, namely November 13, 2012. There you see a slight enhancement of the MUFmax of about ten percent. The geomagnetic storm is lagging behind one to three days the solar activity, as calculated from the sunspots. So, you should use this information surfin’ HF just after a massive enhancement of solar activity – before propagation recedes for a day or so. By the way, a geomagnetic storm doesn’t hit the earth in each case. This has to to with the distorted magnetic field which is no plane but resembling the tutu of a ballerina (not my association …).

Suddenly, a beautiful MUFmax (red line) of greater than 30MHz is more than halved on November 14, 2012, for example. This correlates with geomagnetic activity (grey steps).

Tacitely, I had used the term “MUF” in the sense what is exactly dubbed “MUF(3000)F2”, or: “MUF of the F2 layer when communicating between two stations at a distance of 3000 kilometers”. Ionosondes mostly measure the vertical MUF with transmitter and receiver at the same location, which has to be multiplied by a specifc factor. This factor of about 1,5 to 4 largely depends on the distance of the two stations, and the height of the layer. The following illustration shows propagation between my location and Funchal/Madeira, just 3000 kilometers away in the Atlantic Ocean. At a given height of the refracting layer, one hop gets longer with lowering the elevation of the antenna beam. The lower this angle, the larger the hop. It is a difficult and often expensive task to get this angle under 10° or so, especially at lower bands.

DK8OK -> Funchal, distance 3000km. One-hop propagation is only possible at small antenna beam elevations. Visualization with PropLab 3.1

The illustration below shows the MUFs of ten consecutive days for bridging different distances from 0 (critical frequency, measured directly at the ionosonde) to 4000km. The last distance reckons with a layer height of 330km, being quite optimistic in the years of low solar activity but will be reached easily in other times. Nowadays, the standard is to use MUF(3000), wheras you often find MUF(4000) in legacy literature.

At a given vertical MUF, the oblique MUF is the highe, the greater the distance is – up to a specific limit.

In the last paragraph, I mentioned the height of the refracting layer, and this changes also with solar activity. How, is illustrated by the figure below. There you can see the heights of the four ionospheric layers F2 (highest), F1, E and Es, or Sporadic-E. At the bottom, you find the smoothed sunspot number. You can see that this mostly influences the F2 layer – raising it at high solar activity, and, hence, allowing for larger 1-hop-distances. The height of all other layers follow a much more regular yearly pattern, and are not that much dependant on solar activity.

The height of both F layers, namely F2 and F, is largely dependant on solar acitivity.

This, in turn, leads to the fact that the critical MUFs of each layer, by and large, is matching solar activity. F2 and F layer are mostly influenced by solar activity, as all layers are by the season. See illustration below.

The height of ionospheric layers F2, F1, E and Es, plus smoothed sunspot number – top to bottom.

Just a look on how the MUF changes from day to day under more or less stable solar conditions. With the overall pattern remaining nearly the same, the MUFmax may change considerably, ranging from 20 MHz to well above 30MHz. Nevertheless, at each day you will see a sharp rise before local sunrise (fast iononization) and a flat slope (slower re-combination) directly from around sunset.

How the MUF changed, day by day, over 24 hours on ten consecutive days around the autumn’s equinox – with sunrise and sunset marked.

The following figure shows that there is a high probability to expect today’s propagation also tomorrow – to about 75 percent. There, I used each day of the full twelve years’ period to cover the whole solar cycle.

ow do propagation changes from one day to the next? There is a probability of more than 75 percent that it will be just the same.

Did you ever asked yourself, why important contests and DXpeditions are taking place in spring and autumn, preferably in years of high solar activity? The two following figures will give an answer: the MUF peaks just in these seasons. The peaks are prominent in a year of high solar activity, and not that pronounced in a year of less solar activity.

Yearly MUF changes during high solar activity (2014) …
… and during low solar activity, 2011.

Last, but not least, we now will leave the MUF, heading for power, or, in this case, field strength. The figure below shows hourly measured fieldstrengths on six HF channels from 22.5MHz (top) to 4.3MHz (bottom), normalized to 1kW EIRP from June 1, 1980 to December, 1993, after Deutsche Bundespost had cancelled this project. I added daily smoothed sunspot numbers to the top and the bottom figure. 22.5 MHz has even not been used at all during a time of low solar activity, whereas they stopped using 4.3 MHz from the beginning of a new solar cycle. You can easily spot that some solar activitiy greatly enhances propagation on the channels up from 6.4MHz. In this case, the daily time where you can use the higher channels up from 13.0MHz , also increases. In years of lower solar activity, the time of propagation on the lower channels, down from 8.6MHz, is increased. But this effect is by far not outweighed by the effect on higher frequencies. For these data, we are indebted mainly to Dr. Thomas Damboldt, DJ5DT (1941-2015).

14 and a half years: hourly measured field strengths on six HF channels from 22.5 MHz (top) to 4.3 MHz (bottom) for the path New York -> Norddeich, Northern Germany. Smoothed daily sunspot numbers had been added to both, top and bottom diagram.

To make use of the future you have to know the past. This is easy with cyclic, physical processes. So this look into history is also a look forward into same aspects of solar cycle #25. It will bring better propagation on higher bands, where we may use smaller antennas, face less atmospheric noise and have larger frequency allocations. I am sure that F2 propagation will even take miniscule signals (QRPP) around the world, allowing for daily contacts from Europe to Australia even on 6m – as I had experienced at the peak of cylce #23. Be prepared!

Really 30 years ago? Remembering it like yesterday – daily contacts from Germany with VK6 on 6m over F2 at a daily sunspot number on this October 15, 1991 of 198.

P.S. All calculations/diagrams had been made with Matlab. You may also try it with free Python, matplotbib and Seaborn or other software, you have at hand. With millions of data fields needed, spreadsheet software must be avoided.

HF Propagation: Professional, free, and Real-time

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IRTAM shows the actual state of the ionosphere – see text.

Without proper propagation, world-wide HF communications simply doesn’t exist. We, hams and SWLs, depend on the supporting power of the ionosphere and sometimes struggling with its capricious behavior. Many forecast models had been developed, VOACAP the most prominent among them. Like some far-looking weather models, they deliver broad probabilities – more the climate of the quarter than the weather in the afternoon. Even smart and processor-hungry 3D-raytracing software, taking into account more factors than just the average sunspot number of the month, do face challenges.

Here, IRTAM comes into play. The acronym means “IRI Real-Time Assimilative Mapping”, where IRI stands for the International Reference Ionosphere. This model is the base which is updated by the data of many of so-called digisondes. They are regularily probing the ionosphere at many locations of the world in time increments up to as short as five minutes.

The processed data reveal the actual space weather at this location. Experience, models and clever algorithms are used to spread (assimilate) these results over a world map, and, even more, to produce an animation of the last 24 hours – see the screenshop on the top. Click here to see the last 24 hours.

They show the frequencies, just reflected by the F2 layer under an angle of 90° (vertical sounding). You have to multiply these frequencies with a factor of about 3 to get the highest frequency, being reflected (indeed: refracted) for usual HF communications, or oblique sounding.

Additionally to this, the map will also show e.g. “deviation from climate”. By this map you can compare your VOACAP results (“climate”) to get an impression of the deviations – plus or minus, location, time.

It is a free service of a team around Prof. Bodo Reinisch, supported by world-wide data of their Lowell Digital Ionosondes, the gold standard in this field.

Medium Wave: Signals May tell sunris/Sunset at their transmitter’s site

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The two stronger carriers (Romania left, Algeria right) exhibit Doppler-shifted scatter; see text for a more detailed explanation.

During my expeditions into the thicket of mediumwave offsets, I bumped into pictures like that at the top. In the lower part of the screenshot, you see two carriers mit seahorse-like structures looking to the right. In the evening, they look towards the West.

This is one of the several effects which can be seen at local sunrise/sunset. Here, the carrier gets “clouded” and show frequency changes. These effects are associated with Doppler shift (moving of ionospheric patches/layers) as well as scattering caused by irregularities of the ionosphere, most notably Travelling Ionospheric Disturbances, or TID. Whereas the Doppler shift, by vertical moving of reflecting layers like combining of F1- and F2-layer to one and lower F-layer when approaching darkness, is comparatively small, high wind speeds in these regions can cause a much faster horizontal movement of such regions. This, in turn, may cause a Doppler shift of about 1Hz or even higher in the medium wave range.

The Figure at the top demonstrates this effect at two transmitters on 1422kHz, namely SRR Radio România Actualități from Râmnicu Vâlcea/Olănești (sunrise 05:55 UTC/sunset 15:12 UTC; distance 1433km) and Radio Coran/Radio UFC/Radio Culture/Chaîne 3 from Ouled Fayet/Algeria (sunrise 06:58 UTC/sunset 17:00 UTC; distance 1840 km). Seen from midnight, sunrise first occurs at the Romanian transmitter, followed by the Algerian one with the seahorse-like pattern of the scatter towards the higher frequencies. Around each local sunset, first Romania sees darkness, followed by Algeria. Here, the scatter pattern turns towards the lower frequencies. In the insert at the right, contrast has been sharpened to additionally reveal a split-up of these carriers due to propagation into two paths.

This effect often helps to determine the local sunrise/sunset of a carrier. I marked what presumably is the carrier of MBC Radio 1 from Matiya/Malawi, sunrise 03:22 UTC; listed 02:00 to 22:00 UTC, but obviously on a 24 hours’ service this Tuesday.

Both Figures at the bottom try for some detective work without knowing specific offsets (because not available) but relying only on schedule and the above mentioned propagational effect. Crime scene takes place on 1233kHz, where we want to scrutinize two channels, one on 1232,9937 kHz, the other on 1232,9951kHz.

Distinctive scatter, associated with local sunrise at the transmitter, provides a strong hint towards the location.

The s/off- and the s/on pattern match that of Chinese National Radio #17’s Kazakh service. Incidentally, sunrise takes place in Qinghe at 01:42 UTC, and in Boertala at 02:04UTC – next Figure. Boertala is listed with 10kW (stronger signal), Qinghe with 1kW. Unfortunately, the f/out time of other CNR17 transmitters on this channel is mostly covered by phase noise from Rádio Dechovka in the Czech Republic and Absolute Radio in the United Kingdom.

Some CNR17 locations and the terminator during sunrise in Boertala, see text. Visualized with free Simon’s World Map.

Here I am indebted to Jens Mielich, Head of the ionosonde at Juliusruh/Germany, who was so kind to comment on this observation. According to him, the observed Doppler shift of 1Hz on 1422kHz should have been caused by a refracting medium, moving at an (angular) speed of roughly 105m/s. At Juliusruh, he observed e.g., an ionospheric drift of 311m/s±93m/s from East towards West on January 19, 2021 at 04:19 UTC: “You will get a positive Doppler shift during a West/North drift, and a negative one at East/South drift.” He adds that further investigations on a more longer time series are needed.

PSKOVNDB: An exciting new software for Mediumwave DXers

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See the bunch of carriers on 590kHz at the left. PskovNDB shows at the right a diagram of noise, the combined signal strength of the 200Hz window and the signal strength of the carrier just picked.
Here the very carrier of VOCM/St. John’s had been clicked instead. You easily see that this signal is dominating the channel – only one of the many exciting features of free PskovNDB software!

Recently, I came across an upgraded version of Ivan Monogarov’s PskovNDB software, already having collected all laurels available as being the Gold Standard for chasing non-directional beacon, or NDBs. Recently, Ivan had expanded his tool with some as unique as exciting features for the avid medium wave DXer.

At a first view, it converts recorded WAV files (also: RF64 format, done with SDRC V3 software) into spectrograms of high resolution in which you can easily see the number of stations, measure their precise offset and see their signal strength.

A second view reveals the smart feature of producing diagrams of each signal – plus noise level and the combined power of the whole window. You can see both in the screenshots on top of this page.

A third view almost exactly helps to distinguish between signals where you can here music, listen at least to some words or phrases, or which do provide full audio.

Nothing more? Yes. Under the hood, there is much more. So, you can do automatically recordings each day and also automatically send them to PskovNDB software for showing the spectrograms, one after the other, like on a film roll. This enables you to pick the recording of the most promising day(s) for further inspection.

I wrote a short introduction to the beta version of this free software, and Ivan was so kind to add some most helping notes to this. You can download it here. It contains also some additional information, i.e. a link for downloading the software.

Spassiba, Ivan, for another software breakthrough!

Medium Wave: Offset Atlas – all 9 kHz channels Plus VLF & Longwave, 24 hours

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The “Atlas” shows screenshots of all 9kHz channels on Medium Wave within a 50Hz window, sometimes better. It also shows some odd channels plus Time Signal Stations on VLF and all Broadcasting Longwave Channels. You can download it for free to determine accurate and stable offset readings over 24 hours (zoom in by e.g. 400%)

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; plus longwave on Januar 21, 2021. 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 9kHz on medium wave. You can easily see:

  • sign-on/sign-off
  • fade-in/fade-out
  • 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 865MB. 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.

A similar Atlas showing a raster of 10kHz is also available for free – just scroll to the previous post of this blog. 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.

Medium Wave: Offset Atlas – all 10 kHz channels, 24 hours

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The “Atlas” shows screenshots of all 10kHz channels on Medium Wave within a 50Hz window, sometimes better. You can download it for free to determine accurate and stable offset readings over 24 hours (zoom in by e.g. 400%)

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:

  • sign-on/sign-off
  • fade-in/fade-out
  • 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.

Aloha: KUAU from Haiku/Hawaii, received on January 19, 2021 by DK8OK. Proofs are frequency, plus the rather unique fade-in/fade-out in the European afternoon.

Comments and suggestions are appreciated: dk8ok@gmx.net.

Winter and Spring: Comparing Signal Strengths

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IRAN INTERNATIONAL’s relay station south of Tashkent/Uzbekistan, received on December 16, 2019 (blue line) and April 2, 2020 (yellow line). Day/night below, top pair for Tashkent, lower pair for DK8OK, on the two dates, respectively.

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..

Path Tashkent-DK8OK of Apbil2, 2020 at 16:00 UTC, path length 4550km.

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 …

Receiver: Winradio’s Excalibur Sigma
Antenna: active vertical dipole (2 x 5 m) MD300DX
Software: V3 by Simon Brown, G4ELI, QtiPlot and DX Atlas

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