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Who knows OTA TV? (Dealing with hilly terrain)

Post in 'DIY and General non-hearth advice' started by Badfish740, Jan 14, 2012.

  1. TradEddie

    TradEddie Minister of Fire

    Joined:
    Jan 24, 2012
    Messages:
    701
    Loc:
    SE PA
    There is no inherent difference in signal propagation between analog and digital. In reality, when the change was made, most stations were moved to a different frequency, many needed to buy new transmitters with different signal geometries. A station staying on the same frequency at the same power would generate a decodable digital signal at far greater distances than the analog signal, so in order to save money and limit interference with distant stations, new power levels were calculated to achieve a similar coverage area as the old analog signal.

    The changes in actual frequency and power affect everybody differently. Pre-digital, WHYY (PBS) 12 was unwatchable for me, NBC 10 was perfect, now the PBS channel is perfect and Channel 10 often breaks up. Fair switch.

    TE

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  2. Agent

    Agent Member

    Joined:
    Oct 5, 2011
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    Loc:
    Gillette, WY
    Though the signal propagation may be the same, the signal to picture ratio is very different, and that is the truly frustrating part. Digital is essentially all or nothing for signal and picture quality, where Analog let you still view channels in reduced quality if the signal was bad. Also, it's pretty hard to aim your antenna to find what channels you get when it takes 3 days for some channels to load (even at 75% signal strength!).
  3. TradEddie

    TradEddie Minister of Fire

    Joined:
    Jan 24, 2012
    Messages:
    701
    Loc:
    SE PA
    Absolutely true that digital signals make it much, much more difficult to optimize an antenna location. My TV tuner gives me just 0-7 bars to indicate quality, with no indication of whether this is signal strength, or signal quality. If you a have a lot of multipath interference, signal strength could be fine, but quality is poor. Some tuners give a percentage, which is a little more helpful.

    The "cliff effect" is unfairly giving some digital broadcasts a bad name when in reality the cause is much reduced broadcast strength. Digital signals will give perfect picture quality from signals that if analog would be totally unwatchable due to snow/static. In my case, analog Channel 12 was transmitted at 309kW before the transition resulting in poor picture at my location, it now transmits a 20kW digital signal on the same frequency which gives a perfect picture. If this station was still transmitting at its original strength, you could probably watch Philly TV in Pittsburgh, however you'd also have interference from every station between Boston and Norfolk. Most VHF broadcasts were moved to a different frequency with different propagation characteristics, and the broadcasters have tried to approximate the coverage areas while minimizing interference from, and to, adjacent markets. You can bet if it came down to price which side they chose; lower electricity bill or customer dissatisfaction from a few people who can't afford cable or satellite.

    TE
  4. blacktail

    blacktail Minister of Fire

    Joined:
    Sep 18, 2011
    Messages:
    516
    Loc:
    Western WA
    According to antennaweb.org I can't get reception here. But I do. The previous owner of my house had the antenna and said it only got 3 or 4 channels. I hooked up my tv and get around 20 channels, although many of those are shopping, church, or spanish stations. I wonder if the previous owner got fewer channels because he didn't have a high-def tv. My reception changes a little bit from time to time. Sometimes I'll lose or add a station. For as little as I watch tv, I'll stick with it for free.
  5. I might have misspoke when I said signal propagation wasn't as lengthy with digital. But I have found multiple sources which mention that digital signal are much more susceptible to long distance attenuation and distortion. When you think about it it makes sense. Your mind can interpret a distorted analog signal, can a machine inherently interpret a distorted digital signal? Probably not.
  6. TradEddie

    TradEddie Minister of Fire

    Joined:
    Jan 24, 2012
    Messages:
    701
    Loc:
    SE PA
    That's one part the problem, the new digital broadcast strengths were calculated to produce a decodable signal to approximately the same distance that the old analog signal got snowy, however if you were in a marginal location previously and had become tolerant of the static, chances are you can no longer get a digital picture.
    The bigger part of the problem is usually frequency changes; most VHF stations were moved to UHF. UHF works better in line of sight applications, it generally suffers less from interference, but is less able to "bend" around obstacles or over the horizon than VHF, so people located in valleys, behind trees or on the wrong side of a hill lost out. This is what happened to me, my PBS station stayed on VHF 12 at a much lower power, yet I end up with a much better picture, my NBC station moved from VHF 10 to UHF, and since I'm over a hill from the transmitters, I now lose signal any time the wind blows.

    There is a wealth of information at http://www.avsforum.com/avs-vb/forumdisplay.php?f=6

    TE

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