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#1
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HDTV is inexorably moving across the country, even some XX.1, XX.2 channel
leaking across from XE land. Is this new digital product subject to the same TVI as analog, displaying the same "sound bars", "herringbone", etc., or do we need to decode new artifacts to know if our TVI is from radiated or conducted signals? The Man in the Maze QRM from Baboquivari Peak, AZ --Iitoi |
#2
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HDTV is inexorably moving across the country, even some XX.1, XX.2 channel
leaking across from XE land. Is this new digital product subject to the same TVI as analog, displaying the same "sound bars", "herringbone", etc., or do we need to decode new artifacts to know if our TVI is from radiated or conducted signals? The artifacts seen on digital TV, such as they are, are very different from TVI artifacts on an NTSC broadcast signal. You won't see (or hear) sound bars, hum bars, herringbone, buzz, at all (unless perhaps your TVI is so powerful that it's getting directly into the final, analog stages of the TV... not likely unless you're running a kilowatt right next door). You'll tend to see one of two types of interference artifact on DTV signals: (1) Macroblocking. Square or rectangular portions of the picture will freeze, "tear up" or become monochrome. (2) "Looking for signal" - the whole digital signal "drops out" and the TV blanks the screen and complains. The audio will exhibit analogous dropouts - momentary gaps in the sound, or complete silence when the signal is lost entirely. The character of the artifacts probably won't be terribly useful in figuring out if a ham transmitter is involved... you'll have to depend on the timing (e.g. if macroblocking starts happening when you key-down, your transmitter may be involved). -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#3
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I wonder if this workshop would be useful for some hams to attend (or at least
plug into the audiocast and record it). The Federal Communications Commission has announced the agenda topics and tentative speakers for the Digital Television Consumer Education Workshop to be held Wednesday, September 26, 2007, at FCC Headquarters, 445 12th St., SW, Washington, DC, in the Commission Meeting Room. The Workshop will begin at 8:00 AM and end at 3:45 PM. A live audiocast of the hearing will be available at the FCC's website at http://www.fcc.gov/realaudio/#sep26 on a first-come, first-served basis. In addition, the hearing will be recorded, and the recording will be made available to the public. For further information go to http://fjallfoss.fcc.gov/edocs_publi...C-276258A1.doc The Man in the Maze QRM from Baboquivari Peak, AZ -- Iitoi |
#4
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On Sun, 26 Aug 2007 21:51:07 -0400, Dave Platt wrote:
The artifacts seen on digital TV, such as they are, are very different from TVI artifacts on an NTSC broadcast signal. You won't see (or hear) sound bars, hum bars, herringbone, buzz, at all (unless perhaps your TVI is so powerful that it's getting directly into the final, analog stages of the TV... not likely unless you're running a kilowatt right next door). Though given so many people are on cable/satellite these days, I would suggest that post-demodulator pickup will probably be the more common type of interference... Sound bars, hum bars, and herringbone are all a function of analog reception. You won't notice any of that on a DTV receiver. As Dave says, macroblocking and complete dropouts will be the most common problem. I doubt you'll see any other type of interference to the picture. Direct RF pickup on external audio wiring will probably be a bigger problem. It'll sound just like RFI on stereo equipment. (since that's essentially what it is...) |
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