Category Archives: SDR

RX-888: 32 MHz/16bit, 200 US-$ – pricks up your ears

The RX-888 covers 32MHz @16Bit in a row. Here it comes to life with Simon Brown’s unique and indispensable software SDRC V3 at an professional active dipole antenna MD300DX.

It is the (a few weeks) younger brother to the RX-666, a brainchild of Oscar Steila, IK1XPV. And it is one of the first palm-sized SDRs in the price class of 200 US-$ which covers the whole HF band for receiving, recording and playing with 16Bit resolution, resulting in a competitive dynamic range of about 100dB. I got one from China via eBay (there are numerous sellers) within a few days. Overnight, Simon, G4ELI, made his SDRC V3 software to match also to the RX-888 with excellence. You need a PC, an i5 should do it, with USB3.0 for data streaming, controlling and power supply. Yes, there is no need for a separate 5 or 12VDC!

Much had been speculated about one obvious fact: the price of the A/D chip is, if only a medium order is placed, the same or even higher than the price tag at the RX-888. How comes? One rumor with some substantial background results in this story: the chips had been desoldered from boards of other projects which didn’t pass the quality control. These boards had been sold at a low price as a bonanza to smart people who can use all the parts which on their own will have passed the quality control, most notably the pivotal A/D chip.

This blog should give you a first impression. The biggest difference between RX-666 and RX-888 seems to be that the latter is equipped with a permanent low-noise amplifier of +20dB which perfectly balances sensitivity and dynamic range for 90% of us DXers. The range from 32MHz to ca. 1.8GHz is covered with up to 8MHz/8bit only (R820T2 chip). Sensitivity on HF is nearly on par with FDM-S2.

Two antenna sockets – the impressive cooling fins on three sides of the box will be needed after a planned update of covering 64 MHz in a row with 16Bit, and up to 10MHz (now: 8MHz) above 64MHz.

I tested the RX-888 from 10kHz to 32MHz and had a look above 32MHz – see the two following screenshots.

RJH69 on VLF 25.0kHz. This time signal from Belarus was received at 07:06 UTC on 02SEP2020 in Northern Germany and read with CW decoder MRP40.
A look onto 8MHz of the FM broadcast band.

The RX-888 also worky nicely together with decoders like DRM or (other) data, see the two following screenshots.

The very weak DRM signal of China National Radio on 9655kHz [Urumqui, 30kW, antenna direction 98°!] is duly received by the RX-888 with the data decoded with free DREAM software.
US Air Force Diego Garcia [JDG] in the Indian Ocean calling their Lajes counterpart [PLA] in the Açores on 4721kHz at 17:18UTC in MIL-STD-188-141A.

PC power: Nowadays, a “receiver” is a system, consisting of an SDR (the box), software and the PC. While world-class software SDRC V3 is for free, and an top SDR costs just about 200 US-$, you should not forget an able PC. It must be an i5 and up if you want to digest bigger bandwidth like 8 MHz, 16 MHz or even 32MHz. Even for recording 32 MHz, there is no need for internal SSDs, a fast iron disk will do the job. Furthermore: 32MHz recording for 24 hours do expect a bit more than 11TB disk space. This calls for an external HD, and a second USB3.0 card (not: hub!) is a must. As external HD, I use the WD MyBook Duo, delivering 28TB at under 750 US-$. The combination of an desktop i7 and this HD ensures stutter-free recording and playing up to bandwidth of at least 32MHz. Here simply more is more …

Last, but not least, please find below a few audio examples of broadcast as well as utility stations. They proof that the RX-888 is a serious receiver at a ridiculous low price.

4712 kHz/USB: Russian Airports with radio checks in Russian: Kazan, Rostov (net control), Saratov, Samara, Novosibirsk, Chelayabinsk. They transmit with 1kW of power to a low-hanging dipole. 02SEP2020, 17:00 UTC.
4750kHz/AM-ECSS: Bangladesh Betar with ID over an obviously defective transmitter (nominal 100kW). 02SEP2020, 17:00UTC.
4800kHz/AM-SAM: Chinese National Radio Beijing I (Geermu, 100kW) ID in Mandarin, ID. 02SEP2020, 22:00 UTC.
4920kHz/AM: Tibet People’s Broadcasting Station (Lhasa, 100kW), ID in Tibetan. 02SEP2020, 21:00 UTC.
5000kHz/CW: Chinese Time Signal Station BPM (Sha’anxi/Pucheng, 5kW), ID in CW. 02SEP2020, 22:00UTC.
6676kHz/USB: Singapore VOLMET, 5kW, ID and weather in English. 02SEP2020, 17:20UTC.
6676kHz/USB: Bangkok VOLMET, 5kW, ID and weather in English. 02SEP2020, 18:10UTC.
7240kHz/AM: Tibet People’s Broadcasting Station (Lhasa, 100kW), ID in Mandarin. 02SEP2020, 21:00 UTC.
9275kHz/AM: FEBC Philippines/Bocaue (100kW), ID in Mandarin. 02SEP2020, 14:00 UTC.
9310kHz/AM: VoA Deewa Radio (Udon Thani/Thailand, 250kHz), ID in Pashtun/Urdu. 02SEP2020, 14:00UTC.
9664,77kHz/LSB: Radio Voz Missionaria (Camboriu/Brazil, 10kW), ID in Portuguese. 02SEP2020, 22:00UTC.
10’000kHz/CW: Chinese Time Signal Station BPM (Sha’anxi/Pucheng, 5kW), ID in CW. 02SEP2020, 17:00UTC.

RX-888: 32 MHz, 16 bit – A new standard SDR for HF

A bare sensation: the RX-888 covers 9 kHz to 32 MHz with 16 bit (nearly 100 dB dynamic range) with recording and playing the whole range via USB3.0 which also cares for the power supply. Price: just about 200 US-$.

With the RX-888 just has arrived here, I am busy with testing. The first results a very much encouraging with Simon Brown’s (G4ELI) unique software SDRC V3. More to come within a few days.

Switching-on HF Transmitters: Step by step

Voice of Turkey, Emirler, signing on: 9880 kHz, The ABB transmitter SK5SC3-2P is switched to full poer [500kW] in five steps within about three seconds.

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.

Radio Saudi, signing on, 17’615kHz at 12:57 UTC on 02APR2020. You clearly see at least three different steps of power plus some transient when switiching to full power.

RX-666: Listen to A Gamechanger!

Flying high: RX-666

Since Marco Polo, combinations of Italian and Chinese had proven fruitful. The Dragonfly RX-666 is such a combination or, at least, a very special “kind of”. It is a 16bit SDR, ranging 1 kHz to 30 MHz in a row with 16 bit resolution – plus some extra above 32MHz (1.5/1.7GHz) by the help of an R820T2-chip of RTL-SDR fame, but 8 bit only. Priced not much over US-$ 200 (if that) at some ebay sellers, it is a real gamechanger, offering for the first time 32 MHz streaming via USB3.0 at 16 bit resolution to ensure a competitive dynamic range.

32 MHz at a glance! And just 15% CPU load on an i7.

It has been built around LTC2208 chip and seems a clone, a twin or a pirate piece of a concept, literally layed/laid out by Oscar Steila, IK1XPV, an electronics engineer from Turin. Über-DXer Bjarne Mjelde has diven deep into the story and the receiver itself. I don’t want to repeat what he found out in only my own words. You simply must read his story here, and I can stress each and every word of it.

In this blog, I may add only some audio clips to give an impression of the reception quality in Northern Germany on the evening of August 11 and the morning of August 12, 2020. Antenna, as always, is the professional active dipole MD300DX, vertical with 2 x 5 m legs. Recordings were made with HDSDR software, but replay done with SDRC V3. Both, Bjarne and Oscar, helped me to get the SDR flying at all. Without their friendly hand, it would have been only another heavy paperweight on my desk …

Now for some twelve audio clips:

IRIB Ardabil/IRAN, 1512 kHz, 20:00 UTC in Farsi
RUssian Aero Net with control station like Samara and Ural, 4712 kHz, 20:05 UTC, each running 1kW with a low-hanging dipole; in Russian.
Echo of Hope, clandestine from Suwon/South Korea on 4890 kHz at 20:00 UTC in Korean.
BPM, Chinese time signal station in AM with CW-ID and voice ID in Chinese on 5000 kHz at 19:59 UTC. Please compare to reception during the same time on 10’000 kHz below.
Voice of America/Botswana on 6.080kHz duly doing for what they are payed for: Hail to the Chief, hail, hail, hail! 20:00 UTC
The other chief: TWR Botswana on 6130 kHz in Kimbundu language – Amen. 20:00 UTC
Singapore VOLMET on 6676 kHz with weather e.g. for Kota Kinabalu, Bali, Penang and Singapore/Changi, 19:50 UTC
BPM, Chinese time signal station in AM with CW-ID and voice ID in Chinese on 10’000 kHz at 19:59 UTC. Please compare to reception during the same time on 5000 kHz up.
World Christian Broadcast from Mahajanga/MALAGASY transmitter on 11’965kHz at 20:00 UTC
BBC via their Atlantic Relay/Ascension on 12’095kHz, 20:00 UTC
Radio Kuwait from their homeland on 15’530kHz in Arabic, 05:00 UTC
China Radio International from Kashi/Xinjiang on 17’720kHz in German

The range above 32 MHz is covered by an R820T2-chip at maximum streaming bandwidth of 8MHz only. Please see below a screenshot of a part of the FM broadcast band:

FM broadcast is covered with an R820T2-chip at a maximum streaming bandwidth of 8MHz only. Here you see a part of the FM broadcast band.

FM-DX: How to Identify very short openings – a few examples

42 seconds in a recording of 12 hours length – a “blob” in V3’s “Analyser” module reveals a DX chance.

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 …

First “Stand by me” by a local transmitter, then CHAINE 2 drops in for about 40 seconds, after the local transmitter takes over again.

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.

On an empty channel, a stations pops up for 28 seconds. Pinpointed by V3’s “Analyser”, decoded as RDS “B002” Radio Marca from Na Burguessa/Mallorca in Spain by the RDS decoder.
With a strong local just 100 kHz below, a-symmetrically tuning the bandwidth helps to identifythe very short pop-up of Radio Marca/Mallorca on 91.6 MHz by RDS.

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.

Up to ten seconds in a ten hours’ recording, marked by a rectangle in the spectrogramme: whodunit?
All nine stations carried a broadcast in English, eight of them in parallel, only that on 89.6MHz remaining unidentified. The solution is easy …

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:

Radio Tisnath from Djebel Tissalah/Algeria [2’091km] should carry RDS-ID of “2202 CHAINE2”, which didn’t pop up – in spite of the good signal. At least a station identification was heard, alas, a bit distorted after a programme in Tamazight in the clear
As with all OIRT band stations, also Radio Blagovestiye from Voronezh/G-Tsa Brono in Russia [1’984km) doesn’t carry any RDS information. You have to wait for the announcement – as here – or to collect some other information to identify such a station.

Nĭ hăo, Xinjiang Broadcasting Station!

Still going strong since 1949: Radio Xinjiang, here their banner in Chinese and Mongolian; from their Mongolian website.

Okay, the birthday flowers are already letting hang their heads – but better late than never: Happy birthday, Radio Xinjiang, XJBS!

It was founded in the same year as the People’s Republic of China itself. Only the 1957 edition of the authorative World Radio Handbook took a first notice of their shortwave transmitters at Ürümqi. One of these frequencies, namely 4500 kHz, is still active today.

Among DXers, Radio Xinjiang is a welcomed signal from their transmitters at Ürümqi-Hutubi and at Ürümqi-Changii, some ten kilometeres northwest of Xinjiang’s capital Ürümqi, all in the north-west corner of China.

XJBS’ shortwave transmits in Uighur, Kazakh, Mongolian and Mandarin (“Chinese”) to serve the majority of listeners in each their mother tongue. Please find below their station’s announcement in each of those language. I especially like the “Nĭ hăo, Xinjiang” of the Mandarin recording at second 20. The announcer must have seen Good Morning, Vietnam, undoubtedly echoing Adrian Cronauer [the late Robin Williams].
Just for conaisseurs: in the YouTube clip, Adrian mentioned “Hanoi Hannah”, or Trịnh Thị Ngọ, a popular radio announcer at Radio Hanoi from 1965 airing three shows per day in English, directed towards US GIs. She left microphone only in 1973, after the USA fled from her country.

The following audio clips from my 25MHz/24h recording of December 16, 2019, received with Winradio’s Über-SDR Excalibur Sigma, connected to MD300DX antenna, an active dipole, hung vertical, with 2 x 5m legs.

Mandarin: “Gooood moorning, Xinjiiaaaaang!” 5960kHz, 02:00 UTC
Uighur: 6120kHz, 00:00UTC
Mongolian: 6190kHz, 02:00UTC
Kazakh: 6015kHz, 03:00UTC

I will come back to this interesting station with an analysis of their alltogether 24 HF frequencies between 3950kHz and 13670kHz here in Northern Germany in December 2019, as well as in early April 2020.

P.S. Below a QSL of this station, from 1984 on 4735kHz.

Winter and Spring: Comparing Signal Strengths

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

Propagation Day by Day: CRI Kashi, 15.260 kHz

Signal strengths of CRI/Kashi, day by day, from 08:58 UTC to 09:58 UTC on the nine consecutive days March 15 to March 23, 2020; see text.

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:

All nine signal levels drawn together into one diagram (top), and a small part of it zoomed (bottom) reveals sheer chaos.

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].

The box plot shows very similar signal strengths, day by day. You should concentrate on their each center of gravity. You will also see that the distribution of the signals strengths relative to the center is not symmetrically, with a clearly visible advantage to the percentalge below the average strengths. THis will be covered in some future entry.

Analyzing signal strenghts, is an interesting tool to get to know more about propagation. I will continue this topic – stay tuned!

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

Greyline enhancement

Signal level on 4750 kHz, observed over some hours: After s/off of Bangladesh Betar, People’s Broadcasting Station at Hulun Buir emerged, showing a peak just after their local sunrise

Today’s SDRs plus able software allow for some new insights into propagation. The figure at the top shows but one example: greyline enhancement. It follows the signal levels on 4750 kHz with a resolution of one second. Smoothing this cloud of points, reveals the more general course of signal level. Here we see, after sign off of Bangladesh Betar, the 10 kW transmitter of People’s Broadcasting Station at Hulun Buir coming up. Most interesting is its short-living enhancement just after sunrise at Hailar in China’s Inner Mongolia, squeezed at their borders to Russia and Mongolia.

This greyline enhancement can be observed regularily on frequencies under, say, 10 MHz: at sunrise at the transmitter’s site, first the F2 layer of the ionosphere is building up, being responsible of the signal of, here, about 5 dB. The lower and attenuating D-layer needs a bit more time to build up, leaving a short-living window for an enhanced signal.

This is to encourage also other HF aficionados to to use this technique.

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

CIS Time Signals on VLF

Locations, callsigns and starting times of the received VLF time signal stations, 25 kHz

On January 10, 2020, I did a round-up of VLF time stations from the Commonwealth of Independant States (CIS). They are controlled by the Russian Navy and start their main transmission on 25.0kHz. Then they change to a couple of four other VLF channels. See here for some detailed information in Russian. The diagram below shows a panorama of all received station (Khabarovsk in the Far East missing, as they skip transmission on the 10., 20. and 30. each month) on all frequencies versus time and signal level.

Five locations, six transmissions, five frequencies – this diagram puts it all together.

The diagram features a time resolution of 1s and has a resolution bandwidth of about 0.12 Hz. It is part of a 24h session, made with Winradio’s Excalibur Sigma SDR, active dipole MD300DX (2x5m) and Simon Brown’s software SDRC V3. This software delivers also the values for level over time, which were visualized and combined with QtiPlot software.

Only seemingly, Vileyka and Krasnodar are transmitting on two channels at the same time (from 07:06 UTC/11:06 UTC). This is not the case, but their transmitters show a bit wider signal in their first part of the transmission. Thus, the much weaker (ca. -30dB) “signal” at the same time, but 100Hz up, is some kind of sideband, but not the carrier!

You will see some variation of the carrier power, especially following sign on, but also during the transmission. This can bee seen with tenfold time resolution (i.e. 100ms) and magnifying the dB-scale, see diagram at the bottom as just one example. Fading can be largely excluded for several reasons, artificial characteristic of changes and VLF propagation during short periods among them.

Under the microscope: This rise of 1.5dB of the carrier is part of the workflow of switching on/tuning the transmitter. There are many such details, and they may differ from transmitter, location and performance. Such details might be used for “fingerprinting”.

P.S. The map at the top was made with free software Tableau Public. The locations are geo-referenced, and a satellite map as background will you lead directly to the antennas. Please try this here.

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