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Over the air TV to stop?

Discussion in 'Misc Electronics' started by James Goforth, Jan 10, 2010.

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  1. I have been seeing ads on the TV stating that there's some kind of
    movement which supposedly threatens to end over-the-air TV broadcasts to
    the public -- which doesn't make much sense after all the hassle of
    changing over to Digital broadcasts. What are they talking about?
    It doesn't elaborate on it, and what is even more strange, it doesn't
    even have a website to visit for more info.
  2. Sjouke Burry

    Sjouke Burry Guest

    They might ram internet broadcast down your (our) throat.
  3. Rich Webb

    Rich Webb Guest

    Possible. A link to some of the rumors at

    OTOH, over the air digital is [typically | often | always] (I don't have
    good citations) of better quality than cable or satellite, as it may not
    be as heavily compressed. This could argue for *more* interest in OTA
    HDTV broadcasts.

    OTOH, if it's digital then it can be encrypted, so it may be OTA but
    potentially no longer free.

    OTOH, revenue is revenue and a relatively small proportion of the
    population is OTA only (raises hand). Dumping it altogether and
    auctioning the spectrum could be a quick cash infusion for the Treasury.

    One other item I've seen written about that is being considered is to do
    away with the One Big Antenna system and to seed the service area with
    multiple, low-power transmitters on the cell infrastructure. The
    reasoning seems to be that the ghost rejection in existing DTV receivers
    is already pretty good and could be improved in step with the antenna
    transitions. The result may be cheaper for the broadcaster and could
    potentially allow more OTA channels in a given region.
  4. Is it really possible to use on-channel gap fillers and even build a
    single frequency network (SFN) using 8VSB DTV ?

    I was under the impression that only COFDM DVB-T could properly
    support SFN.
    In Finland two new VHF multiplexes for HDTV are currently bering built
    using COFDM DVB-T2 by a cellular phone company, using their existing
    medium to small (less than 100 m) masts instead of large 300 m masts
    traditionally used for broadcasting.

    The exact same signal is radiated at the same frequency from all
    transmitters in the area, so in practice, a receiver could get a few
    thousand subcarriers from one transmitter and the rest from the other
    transmitter, if there is deep nulls due to multipath on some
    subcarriers from the first transmitter.
  5. starrin

    starrin Guest
  6. Mark Zenier

    Mark Zenier Guest

    A bunch of the high tech outfits want to use the TV bands for part 15
    liscense free wi-fi stuff. This proposed equipment is supposed to be
    smart enough to not jam an active channel, but that's wishful engineering.

    Mark Zenier
    Googleproofaddress(account:mzenier provider:eskimo domain:com)
  7. Charles

    Charles Guest

    It's called scrambling for limited resources. The RF spectrum is a limited
    resource. Currently, radio and TV broadcasters (and others) own a large
    chunk of it. Well, ownership can and will change in this brave new world.
    As the Microsofts and the Googles continue to gain more control of the
    economy, they want more resources.

    It's not necessarily a bad or evil thing. Actually, wideband Internet
    delivery of content can do much more (a better job in many cases) than
    conventional broadcasting. I see the giant competitors merging in the near
    future, if the Democrats will allow that to happen.
  8. If there are empty channels, the broadcasters are not using
    effectively the frequencies allocated for broadcasting.
  9. Don Bruder

    Don Bruder Guest

    Maybe, maybe not - Say channel 6 (just pulling one out of thin air for
    use as an example), is "empty" in "Town A". That doesn't mean channel 6
    isn't being used - It could very well be that it's been deliberately
    left "empty" there because in "Town B", there's a station transmitting
    on it, and if someone were to fire up a transmitter in "Town A" on
    channel 6, it would step on (or be stepped on by) the transmitter in
    "Town B".

    In which case, letting Joe-whoever transmit Wi-Fi on it would very
    likely cause unacceptable interference to reception in "Town A", and
    depending on the power levels involved, could potentially cause trouble
    in "Town B" as well.

    Also, keep in mind that *THE BROADCASTERS* have *VERY* little control
    over which channels they're able to use - Sure, everybody and his dog
    could say "I'm using this channel", but there's this entity here in the
    USA called the FCC, and they've pretty much been made the "dictator for
    life" in almost all aspects of what happens where on the radio spectrum.
    You want to start broadcasting? You ask the FCC for permission, and in
    most cases, they tell you which channel you can use, regardless of what
    channel you might want. You don't play by their rules, they fine you
    multiple thousands of dollars per day until you can't afford to make the
    mortgage payments and have to shut down for lack of a place to broadcast
    from, and/or they come pull your plug for you.
  10. If the intention is to serve Town A with Program A and nearby Town B
    with Program B on the same channel, then the old tradition to use a
    single 300 m tower in each town will fail.

    According to claims in this threads that even current ATSC 8VSB
    receivers would be capable of operating with some kind of single
    frequency network (SFN), using lo to medium power transmitters on
    medium height poles within the town, will help to concentrate the
    signal to the intended reception area and keeping the spill over to
    adjacent cells at acceptable level.
    This is known as the "hidden transmitter problem" as in any CSMA
    network, in which a device in an unfavorable location can not hear
    that there is some other activity on the channel. Thus the device will
    fire up the transmitter thinking that the channel is free.

    I don't think that those devices are going to cause problems in
    locations, in which the TV signal is strong enough for indoor
    antennas, since also the device most likely will hear some activity on
    the channel, even if the signal level would be insufficient for TV
    reception at that spot.

    The situation gets complicated when the TV signal strength is so low
    that directional outdoor antennas must be used. A device in the
    basement would get no TV signal at all and thinking that the channel
    is free, fire up the transmitter and cause interference to TV

    A SFN style TV network would help to keep the TV signal level at
    sufficient levels even indoors, preventing the device from
    transmitting on that channel.

    Practically every country has such organizations for frequency
    coordination. However, at least in US the broadcasters have had a very
    strong lobby groups influencing the FCC.

    Frequency bands are allocated for various services such as
    broadcasting by international agreement within ITU-R (ex CCIR) and the
    allocation is more or less the same at least within a continent.

    In the US, the demands for setting up your own TV station is so high
    that available spectrum would not be sufficient and the FCC tries to
    arbitrate between the various players in the broadcast industry. You
    enemy is not the FCC but the next door TV station, competing for
    frequencies and for income from advertisement.

    The relative importance of broadcasting has been reduced with much new
    technology used by the majority of people, so for instance cellular
    phone lobby groups have much more influence on FCC and similar
    organizations worldwide.

    The cellular and Wi-Fi industry has traditionally had only very narrow
    frequency bands (compared to broadcasting) and hence frequency
    efficiency has been very important from the start.

    However, in broadcast industry, the frequency efficiency has been
    quite bad and the only improvement in frequency efficiency since the
    1930's was the digitalization, allowing 4-6 times the number of
    channels compared to the analog era. On the network level, the
    spectral efficiency is still poor compared to the cellular phone
  11. You still seem to be living in the analog era with big transmitter
    towers :).
    I am fully aware of tropospheric ducting an other tropospheric
    propagation modes.

    The only surprising thing is that the transmitter was on the East cost
    of Florida. Typically this kind of ducting occurs only a few meters
    above water. Radio amateurs have made contacts up to 1000 km up to 10
    GHz with antennas just a few meters above the water front, while
    antennas a few meters higher were useless.

    Perhaps the transmitted signal had reached an elevation just few
    meters above the sea level, when it reached the West cost of Florida,
    before being ducted into Texas.

    Some broadcasting companies have done quite a lot measurements for
    decades to detect such propagation anomalies and the potential for
    interference to their services. Practical experience also show that
    the interference could be so bad that the intended audience is not

    One might expect that similar propagation anomalies would cause havoc
    to cellular phone networks (similar to trying to use a cellular phone
    in an aeroplane), but I have never heard of problems due to
    tropospheric propagation. Apparently the lower tower heights and the
    higher signal levels at the intended service area, will handle most of
    these problems.
  12. Baron

    Baron Guest

    Paul Keinanen Inscribed thus:
    I can confirm that. I've got confirmed qls of 2000 miles on VHF and
    1200 miles on UHF. Winding the tower up caused the signals to get
    weaker and disappear. Another local ham 60ft higher than me broke in
    to ask who I was talking to, because he couldn't hear the other side.
    Dutch VHF television used to be an everyday occurrence here the UK.
  13. The first problem I have with all of this that US telcos are a national
    embarrassment. They state that the FCC has no right to control their
    Internet services as a public utility yet any competition with them
    unleashes lawsuits for unlawful competition with a public utility.
    Until the FCC grows a pair, I'd rather have TV over the air than through
    the telcos.

    The second problem I have with this is Google. Google doesn't really
    give a crap about wireless broadband. Google wants whitespace WiFi
    because they're going to solve interference problems using a large
    geolocation database that can pinpoint exactly where ever Internet
    customer is. I know it sounds too crazy to be true, but search for
    "google geolocation service" and you'll see that it's already online.
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