DRM Test Broadcast on 954 kHz in the Czech Republic

DRM Test Broadcast on 954 kHz from Transmitter in Czech Republic (DRM Consortium)

DRM is now on air in the Czech Republic, on a medium wave channel that used to carry a powerful AM signal. It is broadcast on 954kHz (power reported as 3kW) from the ?eské Bud?jovice transmitter site, located in the South Bohemian region re-using the old AM antenna with a modulator connected to the existing 30 kW AM transmitter.

The DRM transmission on 954kHz was even received in the country using a KiwiSDR.

This is a trial of DRM within the Czech Republic and is scheduled to come to an end possibly in the second half of 2023. The content is supplied by Radiožurnal, a news and journalism station that broadcasts 24 hours a day covering events at home and abroad. The station also carries music in between the news segments.

One of the listeners receiving the DRM signal in the country reported: “From my listening on the remote receivers, it seems to me that a few low-powered AM transmitters could cover the whole country”. [Click here to read the original article…]

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20 thoughts on “DRM Test Broadcast on 954 kHz in the Czech Republic

  1. Mark

    Listening to WINB here in Ireland now on 15755 Khz 8.28 Kbps, this sounds far worse than an internet radio station of the late 90s over dial up.

    Who thinks this is acceptable audio quality and why automatically choose the worse possible quality, the lowest bitrate why not automatically choose a higher bitrate ? 16 Kbps would make a big difference.

    8.28 Kbps is so bad I just struggle to piece back together the missing audio!!!

  2. Cees Smal

    DRM = Doesn’t Really Matter. Testing again? I remember the launch in the late 90s. DRM seems to be in perpetual testing.

    1. mangosman

      India (population 1300 million) has 36 and another 6 are being prepared for DRM high powered transmissions, there is also 3 high frequency high powered transmitters for their international service. A few are pure DRM the rest simulcast AM and DRM for all but an hour a day when they transmit DRM only. The simulcast stations transmit a 2 DRM programs, pure DRM will have 3 programs as well as Journaline text service.
      In 2017 there were 500,000 DRM receiver equipped vehicles now 5.5 million and rapidly rising.
      The Indian Government is about to decide whether to have DRM or HD Radio in the FM band for commercial radio rollout.

      Since 2005 Radio New Zealand Pacific has been transmitting high frequency high power DRM daily to the Pacific Island nations. Late last year they signed a contract for another new similar transmitter.
      The Brazillian Government broadcaster has also let a contract for a high power high frequency DRM only transmitter to cover the Amazon. They tested at very low power for a year, it was heard in a few areas of the USA. When the new transmitter is commissioned it will be true broadcasting including text and images.

      None of this is testing, it is real broadcasting.

      1. Cees Smal

        Radio New Zealand use DRM for FM relays.

        Brazil has no radios on the market.

        AIR had a scandal involving DRM, because certain chief ministers got kickbacks. And won’t even say how many of any people are actually listening.

        1. mangosman

          Since 2005 anyone with a DRM radio can listen to Radio New Zealand and DRM radios are available. South Pacific countries do use it for FM retransmitters a clean much better sounding signal than AM. Sometime this year, this service is going to improve with the new transmitter.

          Brazil, was testing on high frequencies only at very low power with a signal which was reaching the USA, but aimed at the Amazon. Now they are currently building a 100 kW transmitter. The Amazonian tribes are clubbing together to buy receivers and then connecting the output to Wifi transmitter so the village can watch the education programs on tablets.

          Whether there were kickbacks or not, there is a massive network of high powered DRM transmitters on air and at least 5.5 million cars with DRM receivers. When the Indian Government decides on what system to use for a rollout of commercial radio, it will be either DRM or all digital HD radio in the FM band. The USA has no all digital HD radio® broadcasters in the FM band and only 2 on air in the AM band. Existing DRM radios can either receive the new signals or need a software upgrade which the listener can do.
          How many different models of HD Radios® are currently in production for the North American market which are not in vehicles?
          Lastly how many Americans are actually listing to the digital HD signal which is very low power and the receivers blend back to analog. If it is HD2 – HD4 the signal just drops out, when the FM signal is still good.

      2. Mark

        “it will be true broadcasting including text and images.”

        All this sounds good but I hope sound quality is the priority, 8 Kbps is a disgrace and at this point most of the audio has been removed. An AM broadcast sounds vastly superior.

        xHE-AAC needs to be the standard going forward, 20 Kbps minimum.

    2. Mark

      DRM has potential, It really amazes me how well it can travel long distance at low power and still manage such good stable decoding.

      If power costs are an issue DRM is worth investigating but these station owners need to understand that the sound quality matters, and no pontificating at how good DRM sounds because it’s digital matters when it’s compressed to 8 kbps, these DMR promoters immediately lose credibility. Engineers really need to start at 16 kbps absolute minimum and even that in AAC is rubbish but some of these Indian stations use 8 Kbps or near that and it’s so bad it’s just not worth it because there really is no audio left at that low bitrate.

      Digital does not automatically mean good “sound quality”

      Listening now to the last few mins of RRI German broadcast on 7235 Khz, 11.64 Kbps AAC, not great sounding in fairness. Be great to see RRI change to xHE-AAC at 18 Kbps, they’re a big DMR broadcaster so be good to see an upgrade in sound quality.

      If everyone switched to xHE-AAC at 20 Kbps or whatever the max allows, then I’d say sure lets go all DRM

  3. mark

    Another thing that really bugs me about DRM is that even when you have a good signal it won’t decode, I’m trying to listen to Radio Kuwait on 15110 Khz and I get a signal S9 and sometimes a little bit more but absolutely not a hint of it decoding. If this were analogue I could hear it no problem at this signal level.

    1. mangosman

      That transmitter is 200 kW of DRM rms power which is huge. I assume they are using a directional antenna towards Europe increasing the signal strength even more

      If you are using an SDR receiver it is possible the analog to digital converter is being overloaded, thus producing errors. Commonly there is very little filtering of the incoming signal. Thus it is possible that the ADC is overloaded by some other signal which is no where near the wanted signal. The result is that the wanted signal is being modulated by the interference. That will produce intolerable errors.

      I suggest you reduce the RF gain, if not available then insert an attenuator between the antenna and the receiver input to reduce the signal strength.

      1. Mark

        No not overloading, only signal S9 -S9 +5 on my Kiwi SDR with outdoor Antenna.

        I did have an issue with a local Longwave 252 Khz which caused my Kiwi to go nuts, so, the “only” solution was to build a simple band stop filter, there was no commercial alternative, so I built it myself and it made a huge difference to the Kiwi SDR, in fact, I should build one more for Rx on my other receivers because it causes them issues also.

        This can be done for other frequencies that are causing issues, I used this site to get the component values and it worked perfectly, not as tight as it could have been but because there are no other stations above 252 Khz it made no difference.

        LW252 basically makes the ATS 25+ receiver useless , it overloads easy but 252 does not help at all so I need to make a band stop filter for this and my belka DX 100Khz – 30 Mhz is useless on LW due to this 252 Khz also which greatly surprised me, I didn’t think the belka would overload so easy but it only effects LW band, I haven’t yet noticed any overload issues on the Belka on any other band thankfully, it’s a great receiver.

        The malahit DSP 2 also overloads due to 252 Khz but there is attenuator and RF gain so it can deal with it, I really love using the Malahit DSP2 “original” and it sounds absolutely amazing with headphones.

        So back to radio Kuwait, zhongfan yang is probably correct here that it’s some config issue. If true, what a waste.

        Having said that, I have had a lot of issues trying to decode Radio Romania International at times too even with very strong signal S10+

    2. zhongfan yang

      The reason behind the inaudible Radio Kuwait DRM signal on 15110 Khz is the corruption of DRM MSC (Main Service Channel) data: either they miscofig the parameters in the content generator pannel, or someone fall asleep behind the control pannel. If I were their boss, someone should be fired on the spot!

  4. mangosman

    The graphic for this post shows a DRM signal on the left and a pair of AM signals on the right. Note that the DRM signal is flat on top indicating that the power of the digital signal is even.
    The tall spike in the AM broadcasts is the carrier and it contains no sound signals. Surrounding it is the identical sound signals either side. There is nothing except the carrier when transmitting silence and for the highest volume sound a maximum of 33 % of the total power transmitted. This means that the electricity consumed and the output power required of DRM is much less for the same coverage area.

    DRM and for that matter DAB+ do not contain carriers, the advantage of technology which is around 20 years old, rather than the T model Ford era AM and FM which is 70 years old.

  5. mangosman

    All India radio has almost complete coverage of 1300 million people.
    Indian transmitter list https://www.qsl.net/vu2jos/drm/mwk.htm Look at the power! The also have a couple of high power high frequency transmitter which transmit a pair of programs each to international audiences.
    I should add that since 2017 when there were 500,000 cars with DRM, there is now 5.5 million. They are fitted during manufacture at no extra charge.
    The Indian Government is considering the rollout of digital radio for commercial radio. The contenders are DRM or HD Radio®. One FM transmitter transmitting DRM can transmit 18 programs just like DAB+ but because of the lower frequency will cover a larger area. All programs have the same coverage area, but it uses a quarter of the bandwidth of HD Radio®.

    European posters would be aware that the EU makes it compulsory to install terrestrial digital reception in all new cars. Mostly this has meant DAB+. Infotainment systems in cars use a microprocessor which has a Software Designed Radio technology. The difference between DAB+ and DRM is frequency range of tuning and that DRM also has xHE AAC audio compression which is backward compatible to HE AAC used in DAB+. There is software available to manufacturers which combines the programs for both modes and will receive AM and FM as well. I should point out that mobile phones use SDR technology, like KiwiSDR and others. It is used because you can tune a wide range of frequencies using a pair of integrated circuits and produce decoded audio.
    Most SDR radios are capable of over the air software upgrading.

    1. Mark

      I’ve heard the sound quality of some of All India transmissions and it’s absolute rubbish, some of the worst on Shortwave, power savings aside, it’s shocking that anyone could expect someone to listen to as low as 8 Kbps audio quality as they cram 2 streams into one transmission.

      I’ve heard the same positive comments as to the great audio quality of the Amateur radio digital voice modes such as DMR, D-Star and Fusion, Fusion being the best in my opinion but all of them sound very robotic and those that say the sound quality is better than analogue they mean that there is no noise and cracking from lightning or QRM from man made sources, however, the robitic audio can be very bad quality and I prefer listening to a Ham on shortwave in analogue any day.

      This drive to digital has to at some point have some improvement in actual sound quality, from what I have witnessed so far is just pure head killing digital ringing noise, with the exception of Funklust and the MW station on 954 Khz.

      The dramatic reduction in sound quality isn’t worth having station ID on the radio display or some content information displayed. It doesn’t have to be this way of course as I have heard good sounding DRM but poor quality and low bit rate seem to be the accepted norm and this is wrong!

  6. Tim Brockett

    I picked up the Czech DRM broadcast via a Kiwi SDR in France yesterday. It was a clear signal but broke up occasionally. Does anyone have an email address I can send a reception report? Or a postal address?
    I like the sound quality of a solid DRM signal. Short wave is still the only medium that crosses international borders freely and allows people to listen anonymously. The web is great but it can be shut down easily. And using it is hardly an anonymous affair.

  7. Mark

    I received the test on 954 Khz once here in Ireland and was surprised at the audio quality, around 22 kbps if I remember correctly, even if it was only AAC. That extra bitrate makes a notable difference.

    There is strong interference from another Analogue station on that frequency, other than this I would be able to receive it in Ireland every night no problem.

    I’m not a big fan of DRM that use ultra low bitrates 11 kbps AAC which is the majority of DRM transmissions I hear and it’s just head wrecking to listen to it because my brain has to desperately make sense of most of the audio that has been removed due to sheer compression. A good analogue signal even at S5 or S7 sounds vastly superior.

    The best sounding station on DRM has to be Funklust using XHe-AAC , even at 13.38 Kbps it sounds pretty decent but I feel that bitrate could be increased all the same, again, no idea why the lowest possible bitrate has to be chosen ?

    It would be good to see Funklust increase the power because here in Ireland it’s good and stable then nothing for anything up to a minute or even more then can work no problem for 30 mins straight, see with Analogue I’d most likely be able to pick it up all the time, except of course not at the same power level.

    I’m not so sure why the bitrate is so low on most AAC transmissions because it sure sounds shockingly bad and no one in their sane mind would call this acceptable audio quality even for Shortwave where analogue sounds vastly superior. Even if it’s more energy efficient, the sound can be absolutely atrocious.

    I have been very surprised at how efficient DRM can be, for example, being able to receive CNR in the 31m band in the night UTC here in Ireland, and quite stable at times too with only 30Kw of power. That is impressive.

    I think we will never see DRM receivers being sold in Europe in your normal electrical outlets or in cars, with 4G, and 5G now + streaming services and I don’t think we’ll see any MW stations convert either, most if not all the MW transmitters that have been shut down in Europe were shut down never to be reused again and most of the antenna arrays destroyed and the BBC have abandoned many frequencies in the MW band alone in the last 2 years making English transmissions on MW sadly even rarer. Even the BBC said by 2030 they want to end all RF transmissions.

    I’m not sure about anywhere else but most new cars in Europe only come with DAB radio no LW/MW and certainly no SW. It’s as if they are deliberately trying to kill these bands because most radios today are a single chip capable of receiving all bands.

    1. zhongfan yang

      Why using ultra low bit-rate audio codec? Because 1. Constraint on transimssion power, in the case of Funklust, it is only 250W and it has no obligation to serve the whole West European continent. You have to be thankful for whatever data received outside target area. 2. Good quality audio compression algorithm and highly efficient audio codec. Even with the identical audio codec, not all manufactures/designers have the same proficiency to produce audio quality as best as codec allows. And I think the proud Fraunhofer IIS (the provider behind the Funklust’s content server) has every reason to promote their selling point!

    2. mangosman

      https://www.drm.org/wp-content/uploads/2020/05/DRM-Handbook-Version-5.pdf page 19 onwards shows the options and the resulting bit rates. Being Europe in the MF band the signal bandwidth will be 9 or 18 kHz and in the HF band 5, or 10 kHz, band 1 – 3, 100 kHz. If the transmission power is low, then you would want to use 16 levels of QAM to give the biggest defence against noise.

      A good analog signal does not usually contain stereo sound where as in DRM it can.
      Just remember that all smart phones, most new receivers, particularly car infotainment receivers are software designed radios because a pair of chips can produce audio from almost any frequency. With digital radio, you just need to download the appropriate demodulation and decoding program. The differences between DAB+ and DRM are that DRM can use a much wider frequency range, and it also requires xHE AAC decoding. Other changes are firmware values.
      So, except for radios which operate in extreme environments all that is required is an over the air software download to upgrade them to receive MF, HF, VHF band 1, 2, 3 so as to include DAB+. The old DAB has poorer error correction and audio compression and should be sent to the museum which has occurred in all but the UK

  8. Jonathan Marks

    i helped launch DRM in 1996. It should have been out of the testing phase by now. I can’t see how this is ever going to fly, especially with 5 and 6G networks bring so much more and faster.

    1. Mike Bennett

      Thanks for your past columns! So, do you really think that that DAB+, IBOC , DRM are a lost cause, and we are stuck with this crummy, ancient (120 year old!) analogue radio technology for North America , and the rest of the world!…?


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