Short recording of BBC World Service in DRM

Many thanks to SWLing Post contributor, Mangosman, who shares the following off-air recording via the KiwiSDR network and notes:

Attached is a diagram showing the path and the receiver data, the end of a one hour daily broadcast is in the other file. They switched the transmitter back to AM before the end of the station promo.

I listened to the same broadcast on the previous day. It did not have any disturbances over that time. The quality was identical.

That’s a great decode of the BBC in DRM. Thanks for sharing! DRM is such an amazing mode when you get consistent and stable reception. Here in North America, that can be very difficult to achieve, but it’s fascinating when it does happen! Thanks for sharing!

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7 thoughts on “Short recording of BBC World Service in DRM

  1. Mangosman

    Tom,
    The problem with IBOC is the power of the digital signal is tiny to prevent interference between it and the same broadcaster as well as other broadcasters on the adjacent channels. The bandwidth of an HD signal in the FM band is 400 kHz, and HD radio in the AM band 20 kHz. There is a tiny number of all digital HD radio in the AM band which will reduce the bandwidth to the same as for AM analog. There are no all digital FM broadcasts.
    I agree that there is not enough space for DAB+ because most of the band is used by TV channels 7 – 13.
    What is available is TV channels 2 – 6 which is virtually deserted. There are more channels available than the total in the AM and FM bands if DRM is used. A DRM channel in this band is half the width of an analog FM transmitter and the power does not have to be reduced for interference to FM broadcasts.
    Lastly the bit rates for HD radio are so low, audio gives poor quality audio, made worse by an old inefficient data compression system. DRM uses the latest most efficient data compresssion.

    Reply
    1. Tom Servo

      You’re right about the low bitrates but honestly HD sounds better to me on a well-engineered hybrid digital AM station than anything I’ve heard from DRM (AM in India, SW elsewhere), and better than SiriusXM audio, which is especially terrible sound quality. But no one seems to care, as everyone streams low bitrate streams and listens to SXM without complaint, so I think we are in the minority caring about sound quality. A good FM HD broadcast is noticeably better quality than virtually any webstream, too.

      I do wish the FCC had the foresight to reallocate the VHF low band to radio with an incentive to migrate AM over; this has happened recently in Brazil. They allocated 76-88 MHz as an expanded FM band and any radio imported with the Japanese FM band will immediately be able to receive the new signals. It gives them an outlet to get existing AMs over in major metros where there were no conventional frequencies left.

      An expanded band could have mandated digital-only operation which would eliminate the low bitrate issue as well as the low power issues and negate the need to bring in yet another digital standard like DRM.

      Reply
  2. Mike

    I copied the BBC in DRM on 3955 KHz around 2:00 AM local time here in western Massachusetts on September 5th on my KiwiSDR. I was surprised – I’d seen the BBC in DRM on that frequency before but I don’t think I ever got a solid enough lock to get near-flawless audio like I did that night.

    Reply
  3. Mangosman

    Mike,
    DRM will operate in all broadcasting bands from 148 kHz to 230 MHz. There was also text data which I was not able to decode. Journaline is an indexed text service which can contain up to 4000 A4 pages. However you can insert images which will reduce this. Typically used for emergency warnings and news.

    I have advocated that since there are virtually no high powered and very few low powered TV transmitters in North America within the channel 2 – 6 range, that could be turned over to DRM. You can transmit 3 high quality sound programs plus some images and text per channel, which is half the width of an analog FM channel or one quarter of the width of an HD channel. In addition to prevent interference with the stations’ FM signal, the HD radio digital signal is very weak. In DRM there is no such restriction and you can leave your original analog FM signal going until FM switch off.

    I should also point out that in North America and South Korea, ATSC 1.0 was selected for digital TV and analog NTSC TV was switched off. Now ATSC3.0 is using the COFDM modulation of the DVB-T and ISDB systems used in the rest of the world. This modulation is excellent in ignoring reflected signals common in cities. Australia has been using it since 2001 as it was invented in Australia by a team of radio astronomers.

    Reply
  4. Yoshio Anda

    I am located in Shanghai, China (I am a Japanese working in China) and listened to BBCWS DRM on Sep 5, 2021. The following is the link to my short recording: https://youtu.be/8J5RpaBnRwo

    It’s not so easy to receive the DRM signal transmitted from Kranji, Singapore, here in Shanghai, either. I feel happy when I have successful decoding.

    Reply
  5. Mike Bennett

    …why is America always behind in adopting KOOL technologies…in this case radio transmission? It didn’t use IBOC, so why get stuck with 120 year old analog radio transmissions? Let’s drop our pride (America always must be FIRST!), and adopt DRM, or something better than what North America has NOW!

    Reply
    1. Tom Servo

      The US does use IBOC, and there are hundreds of stations and millions of car radios that can decode it. It’s mostly used to feed analog translators in major markets, but that doesn’t mean it’s a failure, it just found a use different from what was intended. Many public broadcasters use it to feed a fulltime talk or classical feed in addition to their main programming. Even in my small market, there are three or four unique formats on HD subchannels that I can’t hear any other way except online. And if you’ve been to the US, you know our cellular networks are crap and not easily capable of streaming once you leave an urban area.

      We simply do not have the spare spectrum to roll out DAB+ like Europe, and we don’t have national networks like the European market does. DRM probably would have worked better for us in the long run but it was a case of “not-here-ism”. It wasn’t invented here, so we don’t want it. Dumb, but that’s life in the big city.

      As for “KOOL” technologies, we did have a go at AM stereo, and nationwide satellite broadcasting via SiriusXM is still unique to us, too.

      Reply

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