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Thread: ATSC 3.0, the Spectrum Auction and the future of DTV dxing

  1. #1
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    Default ATSC 3.0, the Spectrum Auction and the future of DTV dxing

    I just read today on an electronics blog that the major television manufacturers globally are seriously contemplating REMOVING tuners from future television sets. The general remarks about this on that blog were aimed at these three factors-


    • The *possible* impending transition to ATSC 3.0 in the United States;
    • Since the abandonment of NTSC in most countries, no single digital transmission standard has been established globally;
    • The desire for inter-connectivity of wireless devices to large format video displays.


    The implications are that the electronics industry does NOT want to go through another expensive transition (ATSC 1.0 > ATSC 3.0) in such a short time. This means your television viewing experience becomes an à la carte adventure. You start with a monitor aka video screen. Then you add the devices you are interested in. Some people watch OTA TV. You add the appropriate HDTV interface component (ATSC 3.0 tuner module/USB dongle/etc), along with any other devices you care to have in your entertainment mix. I have a friend in Denver that is on Comcast for internet ONLY. They gave him an ATSC 1.0 tuner box complimentary when he signed up. Its still in the manufacturer box, stuck away somewhere in a closet. He DOESN'T watch OTA television. He DOESN'T pay to watch TV. He gets his entertainment via internet.

    The real curiosity of this post is because ATSC 3.0 is a reality and will be deployed sooner than we think - AND - the Spectrum Auction is a reality. Everything above RF 38 in the United States is going to go somewhere else. And I also understand that the FCC has NOT mandated to broadcast television stations that they HAVE to switch to ATSC 3.0, like they did with NTSC going to ATSC. So - what is going to happen to the future of DTV dxing???? Does anyone really know?

    TV Technology posted this story WAYYY back mid 2015, getting us ready for ATSC 3.0....
    http://www.tvtechnology.com/expertis...atsc-30/276660

    The ATSC organization posted this on their blog in early December 2016, regarding WHY....
    http://atsc.org/newsletter/why-atsc-3-0-opportunity/

    And finally, the people that are following this very closely, HD Guru, posted this update on ATSC 3.0 on December 19, 2016....
    https://hdguru.com/decision-on-atsc-3-0-hdr-now-expected-in-january/

    When you do the research on ATSC 3.0, its easy to figure out what the technology will do for multiple video/audio streams that ATSC 1.0 can NOT do. What I am having a hard time finding through research is WHY the ATSC 3.0 signal will be EASIER to decode than ATSC 1.0 signals. If ATSC 3.0 is using the SAME terrestrial broadcast approach, what makes reception better? And IF that is true, with the reduced amount of spectrum from the auction, the bottom line question is.....

    Aren't we looking at impending chaos with decode reliability when signals are enhanced due to Tropospheric scatter/ducting or Sporadic E reception? I especially appreciate any comments from the engineers in the know on this subject.

    -I forgot to add this link, which is a *rant* about ATSC 3.0, courtesy of Solid Signal, the company that sells all of us antennas and various electronic items....
    http://forums.solidsignal.com/conten...hould-not-care
    Last edited by Jim Thomas; 01-22-2017 at 10:48 AM. Reason: Additional comments
    Jim Thomas
    Springfield, MO

    Ozark Mountain DTV dxing Daredevil

    Dx Equipment - AntennaCraft MXU59 UHF antenna & homebrew version of AntennaCraft Y10-7-13 VHF antenna @ 25'. Both antennas fed through a Winegard HDP-269 12dB pre-amp; a Zenith DTT901 converter box & a Silicon Dust HDHomerun Dual ATSC tuner, using Rabbitears autologger support.

  2. #2
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    Quote Originally Posted by Jim Thomas View Post
    When you do the research on ATSC 3.0, its easy to figure out what the technology will do for multiple video/audio streams that ATSC 1.0 can NOT do. What I am having a hard time finding through research is WHY the ATSC 3.0 signal will be EASIER to decode than ATSC 1.0 signals. If ATSC 3.0 is using the SAME terrestrial broadcast approach, what makes reception better?
    For one, the modulation scheme is far less prone to errors. ATSC 1.0 uses 8VSB modulation. All the other digital television standards (DVB-T/T2, ISDB-T, DTMB and ATSC 3.0) use OFDM modulation (used for cellular and other signals as well) instead of 8VSB.
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  3. #3
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    8VSB, like analog, uses a single carrier. That carrier carries all 19 million bits of data broadcast each second. If something interferes with that carrier, the entire datastream is lost. There is error correction in the protocol -- it can recover from some amount of data loss -- but if the interference happens too often or goes on too long, the error correction can't keep up.

    ("interference" includes noise and multipath)

    OFDM uses *multiple* carriers. Thousands of them. Each carrier carries a small part -- less than 1% -- of the datastream. As many as a few hundred of these carriers can suffer interference and the error correction will still be able to keep up & deliver a viewable stream.

    Local stations use OFDM on their live trucks. (indeed, they use the same DVB-T standard used by OTA stations in Europe, though obviously at far lower power and about 3 times the frequency) The reliability is pretty stunning.


    So why didn't we use OFDM for ATSC 1.0? Sinclair asked the FCC to allow stations to choose OFDM *or* 8VSB; the FCC declined. IMHO a mistake.
    There is a downside to OFDM though.
    OFDM, 8VSB, and analog are not frequency-modulated modes. The transmitted power is continuously changing. The peak-to-average power ratio (PAPR) for OFDM is higher than for 8VSB. This means that many of the components in the transmission system must be larger for the same power level. For example, the feedline carrying the power up to the antenna must be large enough in diameter that the peak voltage doesn't cause it to arc over. The transmitters in our live trucks are multimode. They're capable of delivering 12 watts of analog FM power - but only four watts of OFDM. (though I should say, that 4 watts of OFDM delivers a full quality signal at the same distance as the 12 watt analog signal)


    There is another feature in ATSC 3.0 that improves decoding reliability: hierarchical modulation. Three bitstreams are transmitted simultaneously: a few bits of a low-resolution stream (roughly what you'd watch on your phone); a medium-bandwidth stream (roughly SD quality); and a high-bandwidth stream. (4K) The lower bitrate streams can take more data loss and still decode; the higher bitrate streams deliver a better picture but can't tolerate as much interference. So it's a *bit* like analog: in the presence of interference the picture doesn't go away entirely, it just loses some quality.
    Doug Smith W9WI
    Pleasant View, TN EM66
    http://www.w9wi.com

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