Visual "clipping"? - Other Technologies

This is a discussion on Visual "clipping"? - Other Technologies ; Gene E. Bloch wrote: > On 9/04/2007, Michael A. Terrell posted this: >> "Gene E. Bloch" wrote: >>> >>> On 9/04/2007, Michael A. Terrell posted this: >>>> Martin Heffels wrote: >>>>> >>>>> On Tue, 04 Sep 2007 12:23:52 -0400, "Michael ...

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Visual "clipping"?

  1. Default Re: Visual "clipping"?

    Gene E. Bloch wrote:
    > On 9/04/2007, Michael A. Terrell posted this:
    >> "Gene E. Bloch" wrote:
    >>>
    >>> On 9/04/2007, Michael A. Terrell posted this:
    >>>> Martin Heffels wrote:
    >>>>>
    >>>>> On Tue, 04 Sep 2007 12:23:52 -0400, "Michael A. Terrell"
    >>>>> <mike.terrell@earthlink.net> wrote:
    >>>>>
    >>>>>> Never worked at a TV transmitter site, have you? If they are
    >>>>>> operating under the specified power, they are in violation of their
    >>>>>> license, and no one is stupid enough to overbuy on the transmitter
    >>>>>> requirements.
    >>>>>
    >>>>> Help me here..... Since when would this be a violation? A
    >>>>> transmitter-license usually states the _maximum_ amount of power,
    >>>>> so what
    >>>>> is different here? Stories are plenty of radio and television-stations
    >>>>> cutting down their power for power-saving reasons (money, money,
    >>>>> money).
    >>>>
    >>>>
    >>>> In the US a station has to notify the FCC if they are not operating
    >>>> at the power they are licensed for. It has to be logged on a set
    >>>> schedule and kept in the station's permanent files for the FCC field
    >>>> inspectors. If a station is operating below the level they are
    >>>> licensed
    >>>> for, they are not serving the area they agreed to provide service to.
    >>>> VERY few stations were ever allowed to differ from their rated power.
    >>>> The only two I ever saw were on military bases where the transmitter
    >>>> power was listed, with "Or as deemed necessary". These were in remote
    >>>> locations and major repairs were consider as 'Depot Level' repairs.
    >>>> Reduced or increased power was allowed, to stay on the air, but none of
    >>>> these were high power stations. The license was deemed a 'Courtesy
    >>>> License' by the FCC, which meant that they had little authority over a
    >>>> military transmitter, but the 'Courtesy License' was granted to make
    >>>> sure the frequency coordinators didn't assign a civilian station an
    >>>> allocation that would interfere.
    >>>>
    >>>>
    >>>> If your power level is too high, you can cause problems for other
    >>>> stations, and if it's too low, your advertisers will demand refunds.
    >>>>
    >>>> I was a broadcast engineer at one military and two civilian TV
    >>>> stations over a 17 year period. I lost count of the AM radio
    >>>> stations I
    >>>> did work for, or located parts and equipment to keep on the air.
    >>>
    >>> However, the original remark was not about the *licensed* power, it was
    >>> about the *rated* power. I.e., the electrical or electronic limits, not
    >>> the legal limits.

    >>
    >>
    >> Its obvious that you've never built a TV station from the ground
    >> up. Even a spare 10% transmitter power capacity could cost a couple
    >> hundred
    >> thousand dollars in capital assets. and its unlikely the governing
    >> agency will allow you to use equipment capable of excess power, any more
    >> than you can build whatever tower height you want. It costs millions of
    >> dollars to build a full power commercial TV station.

    >
    > Do you *really* think I've never built a TV station form the ground up?
    >
    > Really?
    >
    > Well, you're correct. It doesn't keep from speculating, however.
    >
    > For example, it *might* be true that it's a good idea to spend extra
    > money to put in safety factors (although, to be fair, I *do* run my 100W
    > lightbulbs at 100W). It could be cheaper in the long run than fixing the
    > reasult of not doing so.
    >
    > The above has certinaly been true in civil construction for millennia.
    >

    Oh. So that's why small rural bridges never have weight limits posted
    on them?

    Not.

    Any system has to be designed with some sort of limits in mind. If the
    broadcasters want to make decisions about how much of a screen can be
    black and for how long, it's their decision to make.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Do you need to implement control loops in software?
    "Applied Control Theory for Embedded Systems" gives you just what it says.
    See details at http://www.wescottdesign.com/actfes/actfes.html

  2. Default Re: Visual "clipping"?

    Matt Ion wrote:
    > Richard Crowley wrote:
    >> "isw" wrote ...
    >>> Radium wrote:
    >>>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
    >>>> monitors?
    >>> No. Prolonged blacks can damage television transmitters, however (video
    >>> is inverted for transmission, so black requires full power from the
    >>> transmitter).

    >>
    >> Prolonged bright areas (whether clipped or not) will damage CRT
    >> monitors. I have two on the bench right now to have their CRTs
    >> replaced because the image is burned-in. They came from a
    >> security/survelience application and you can somewhat see the
    >> hallway and the doors they were monitoring.

    >
    > ANY static image for a prolonged time will cause burn-in on a CRT or
    > plasma display. The brighter it is, the less time it takes, but it
    > doesn't have to be pure white for burn to occur. Simply displaying 100%
    > white won't cause instant death of a monitor, however, the way a clipped
    > signal can damage a speaker.


    Speaker damage occurs when the *speaker* clips. It's a result of the
    voice coil hammering against the stops. Woofers and midranges are
    protected from the high frequencies that clipping in the amplifier
    generates by their crossover networks. If a tweeter isn't underrared as
    tweeters often are, they won't be damaged by the acceleration forces.
    When an amplifier clips, there's no longer feedback to lower its output
    impedance, and the high output impedance also protects the speaker from
    amplifier overload.

    There are few speakers that can withstand the full output of a 500 W
    amplifier even when the amplifier doesn't clip. Speaker ratings apply to
    short bursts of power, not continuous abuse. A 10%-efficient speaker
    driven at 500 watts is having 450 W of heat pumped into it. A two-slice
    toaster runs about 800 W. How long before the voice coil smokes?

    Transmitter and amplifier tubes have two ratings: CCS and ICAS*. There
    is significant difference. Speakers are rated what I call MDFR**. What
    will the salespeople tell you, that the rating is bogus or that clipping
    burned it out?

    Jerry
    ________________________________________
    * "Continuous commercial service" and "intermittent commercial and
    amateur service".
    ** "Market-driven fictitious rating"
    --
    Engineering is the art of making what you want from things you can get.
    ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

  3. Default Re: Visual "clipping"?

    "Gene E. Bloch" wrote:
    >
    > > On 9/04/2007, Michael A. Terrell posted this:
    > >
    > > Its obvious that you've never built a TV station from the ground up.
    > > Even a spare 10% transmitter power capacity could cost a couple hundred
    > > thousand dollars in capital assets. and its unlikely the governing
    > > agency will allow you to use equipment capable of excess power, any more
    > > than you can build whatever tower height you want. It costs millions of
    > > dollars to build a full power commercial TV station.

    >
    > Do you *really* think I've never built a TV station from the ground up?
    >
    > Really?
    >
    > Well, you're correct.



    I HAVE built a complete TV station, starting with an empty building
    and no tower.


    > It doesn't keep from speculating, however.



    Speculate all you want, and let everyone see that you have absolutely
    no grasp of the subject.


    > For example, it *might* be true that it's a good idea to spend extra
    > money to put in safety factors (although, to be fair, I *do* run my
    > 100W lightbulbs at 100W). It could be cheaper in the long run than
    > fixing the reasult of not doing so.



    Do you know that a TV station's EIRP is transmitter power output,
    multiplied by antenna gain?


    > The above has certinaly been true in civil construction for millennia.



    The only 'Civil' Engineering of a TV station is the buildings, and
    the towers. The rest is Electronics, which is a different discipline,
    with different rules.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida

  4. Default Re: Visual "clipping"?

    Michael A. Terrell wrote:
    >[snip]
    >
    > Never worked at a TV transmitter site, have you? If they are
    > operating under the specified power, they are in violation of their
    > license, ...


    *WHAT?*
    Please quote a specific regulation that _prohibits_ operating at *LESS*
    than authorized power. My commercial license (2nd class phone) may have
    expired 40 years ago, but I never heard of such. We even had a backup
    1Kw transmitter for when our 50Kw transmitter went down. There were
    occasions (ice storms) when we switched to backup BEFORE primary went
    down as it was more tolerant of bad SWR. [now this was an FM rather than
    TV but don not see difference for this case]





  5. Default Re: Visual "clipping"?

    Michael A. Terrell wrote:
    > Martin Heffels wrote:
    >> On Tue, 04 Sep 2007 12:23:52 -0400, "Michael A. Terrell"
    >> <mike.terrell@earthlink.net> wrote:
    >>
    >>> Never worked at a TV transmitter site, have you? If they are
    >>> operating under the specified power, they are in violation of their
    >>> license, and no one is stupid enough to overbuy on the transmitter
    >>> requirements.

    >> Help me here..... Since when would this be a violation? A
    >> transmitter-license usually states the _maximum_ amount of power, so what
    >> is different here? Stories are plenty of radio and television-stations
    >> cutting down their power for power-saving reasons (money, money, money).

    >
    >
    > In the US a station has to notify the FCC if they are not operating
    > at the power they are licensed for. It has to be logged on a set
    > schedule and kept in the station's permanent files for the FCC field
    > inspectors. If a station is operating below the level they are licensed
    > for, they are not serving the area they agreed to provide service to.
    > VERY few stations were ever allowed to differ from their rated power.
    > The only two I ever saw were on military bases where the transmitter
    > power was listed, with "Or as deemed necessary". These were in remote
    > locations and major repairs were consider as 'Depot Level' repairs.
    > Reduced or increased power was allowed, to stay on the air, but none of
    > these were high power stations. The license was deemed a 'Courtesy
    > License' by the FCC, which meant that they had little authority over a
    > military transmitter, but the 'Courtesy License' was granted to make
    > sure the frequency coordinators didn't assign a civilian station an
    > allocation that would interfere.
    >
    >
    > If your power level is too high, you can cause problems for other
    > stations, and if it's too low, your advertisers will demand refunds.
    >
    > I was a broadcast engineer at one military and two civilian TV
    > stations over a 17 year period. I lost count of the AM radio stations I
    > did work for, or located parts and equipment to keep on the air.


    At least at one time, a station's backup transmitter could have lower
    power than it's main, and anything went if it was the only way to put a
    station on the air at all. Nobody liked it, but it was considered better
    than dead air.

    Jerry
    --
    Engineering is the art of making what you want from things you can get.
    ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

  6. Default Re: Visual "clipping"?

    Richard Owlett wrote:
    >
    > Michael A. Terrell wrote:
    > >[snip]
    > >
    > > Never worked at a TV transmitter site, have you? If they are
    > > operating under the specified power, they are in violation of their
    > > license, ...

    >
    > *WHAT?*
    > Please quote a specific regulation that _prohibits_ operating at *LESS*
    > than authorized power. My commercial license (2nd class phone) may have
    > expired 40 years ago, but I never heard of such. We even had a backup
    > 1Kw transmitter for when our 50Kw transmitter went down. There were
    > occasions (ice storms) when we switched to backup BEFORE primary went
    > down as it was more tolerant of bad SWR. [now this was an FM rather than
    > TV but don not see difference for this case]



    That is an emergency situation, not normal operation. If any single
    emergency lasted more than three days, the FCC required notification. If
    a station is 'dark' more than a set number of days because of equipment
    failure, they can lose their operating license, and have to fight anyone
    else who wants that frequency allocation when they reapply for a
    operating license. They may also be required to repalce any oldder, adn
    all defective equipment that was grandfathered under the old operating
    license.


    All the FCC requlations are part of Title 47 CFR, so help yourself at
    the link below. There are months of reading involvled to wade through
    all of it.

    http://www.gpoaccess.gov/cfr/index.html

    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida

  7. Default Re: Visual "clipping"?

    Richard Crowley wrote:
    > "Gene E. Bloch" wrote ...
    >> However, the original remark was not about the *licensed* power, it was
    >> about the *rated* power. I.e., the electrical or electronic limits, not
    >> the legal limits.

    >
    > But as Mr. Terrell also observed, profit-making businesses don't
    > commonly waste money buying an over-powered transmitter.
    > They are frightfully expensive in any case.


    No engineer would design a 500 KW transmitter that would burn out 502.
    Can you imagine a bus coming to a bridge so tightly rated that the
    driver calls for three passengers to walk across after the bus makes the
    far side in order not to overload the bridge? If you wanted to design a
    bridge that would safely carry the unloaded bus but fail with the extra
    three passengers on board, could you? TV transmitters have substantial
    built-in safety factor.

    Jerry
    --
    Engineering is the art of making what you want from things you can get.
    ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

  8. Default Re: Visual "clipping"?

    Michael A. Terrell wrote:

    ...

    > Its obvious that you've never built a TV station from the ground up.
    > Even a spare 10% transmitter power capacity could cost a couple hundred
    > thousand dollars in capital assets. and its unlikely the governing
    > agency will allow you to use equipment capable of excess power, any more
    > than you can build whatever tower height you want. It costs millions of
    > dollars to build a full power commercial TV station.


    You need to distinguish between rated capacity and transient overload
    capacity.

    My sewage plant is rated 20 million gallons a day. During periods of
    heavy rain (and therefore groundwater infiltration) it regularly
    processes 26 MGD without violating any discharge limits. After a few
    days, however, effluent quality suffers.

    Certain floors are required by code to carry 300 lb./sq.ft. If such a
    floor fails catastrophically at 350 lb./sq.ft., the designer could well
    lose his license.

    Jerry
    --
    Engineering is the art of making what you want from things you can get.
    ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

  9. Default Re: Visual "clipping"?

    Tim Wescott wrote:
    > Gene E. Bloch wrote:
    >> On 9/04/2007, Michael A. Terrell posted this:
    >>> "Gene E. Bloch" wrote:
    >>>>
    >>>> On 9/04/2007, Michael A. Terrell posted this:
    >>>>> Martin Heffels wrote:
    >>>>>>
    >>>>>> On Tue, 04 Sep 2007 12:23:52 -0400, "Michael A. Terrell"
    >>>>>> <mike.terrell@earthlink.net> wrote:
    >>>>>>
    >>>>>>> Never worked at a TV transmitter site, have you? If they are
    >>>>>>> operating under the specified power, they are in violation of their
    >>>>>>> license, and no one is stupid enough to overbuy on the transmitter
    >>>>>>> requirements.
    >>>>>>
    >>>>>> Help me here..... Since when would this be a violation? A
    >>>>>> transmitter-license usually states the _maximum_ amount of power,
    >>>>>> so what
    >>>>>> is different here? Stories are plenty of radio and
    >>>>>> television-stations
    >>>>>> cutting down their power for power-saving reasons (money, money,
    >>>>>> money).
    >>>>>
    >>>>>
    >>>>> In the US a station has to notify the FCC if they are not operating
    >>>>> at the power they are licensed for. It has to be logged on a set
    >>>>> schedule and kept in the station's permanent files for the FCC field
    >>>>> inspectors. If a station is operating below the level they are
    >>>>> licensed
    >>>>> for, they are not serving the area they agreed to provide service to.
    >>>>> VERY few stations were ever allowed to differ from their rated power.
    >>>>> The only two I ever saw were on military bases where the transmitter
    >>>>> power was listed, with "Or as deemed necessary". These were in remote
    >>>>> locations and major repairs were consider as 'Depot Level' repairs.
    >>>>> Reduced or increased power was allowed, to stay on the air, but
    >>>>> none of
    >>>>> these were high power stations. The license was deemed a 'Courtesy
    >>>>> License' by the FCC, which meant that they had little authority over a
    >>>>> military transmitter, but the 'Courtesy License' was granted to make
    >>>>> sure the frequency coordinators didn't assign a civilian station an
    >>>>> allocation that would interfere.
    >>>>>
    >>>>>
    >>>>> If your power level is too high, you can cause problems for other
    >>>>> stations, and if it's too low, your advertisers will demand refunds.
    >>>>>
    >>>>> I was a broadcast engineer at one military and two civilian TV
    >>>>> stations over a 17 year period. I lost count of the AM radio
    >>>>> stations I
    >>>>> did work for, or located parts and equipment to keep on the air.
    >>>>
    >>>> However, the original remark was not about the *licensed* power, it was
    >>>> about the *rated* power. I.e., the electrical or electronic limits, not
    >>>> the legal limits.
    >>>
    >>>
    >>> Its obvious that you've never built a TV station from the ground
    >>> up. Even a spare 10% transmitter power capacity could cost a couple
    >>> hundred
    >>> thousand dollars in capital assets. and its unlikely the governing
    >>> agency will allow you to use equipment capable of excess power, any more
    >>> than you can build whatever tower height you want. It costs millions of
    >>> dollars to build a full power commercial TV station.

    >>
    >> Do you *really* think I've never built a TV station form the ground up?
    >>
    >> Really?
    >>
    >> Well, you're correct. It doesn't keep from speculating, however.
    >>
    >> For example, it *might* be true that it's a good idea to spend extra
    >> money to put in safety factors (although, to be fair, I *do* run my
    >> 100W lightbulbs at 100W). It could be cheaper in the long run than
    >> fixing the reasult of not doing so.
    >>
    >> The above has certinaly been true in civil construction for millennia.
    >>

    > Oh. So that's why small rural bridges never have weight limits posted
    > on them?
    >
    > Not.
    >
    > Any system has to be designed with some sort of limits in mind. If the
    > broadcasters want to make decisions about how much of a screen can be
    > black and for how long, it's their decision to make.


    Do we know that the final of a TV transmitter has the most dissipation
    when it's outputting the most power? IIRC -- it was 1957 when I last had
    to know -- those finals operate class B linear. Such amplifiers
    experience maximum dissipation at well below full output.

    J
    --
    Engineering is the art of making what you want from things you can get.
    ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

  10. Default Re: Visual "clipping"?

    Jerry Avins wrote:
    >
    > Michael A. Terrell wrote:
    > > Martin Heffels wrote:
    > >> On Tue, 04 Sep 2007 12:23:52 -0400, "Michael A. Terrell"
    > >> <mike.terrell@earthlink.net> wrote:
    > >>
    > >>> Never worked at a TV transmitter site, have you? If they are
    > >>> operating under the specified power, they are in violation of their
    > >>> license, and no one is stupid enough to overbuy on the transmitter
    > >>> requirements.
    > >> Help me here..... Since when would this be a violation? A
    > >> transmitter-license usually states the _maximum_ amount of power, so what
    > >> is different here? Stories are plenty of radio and television-stations
    > >> cutting down their power for power-saving reasons (money, money, money).

    > >
    > >
    > > In the US a station has to notify the FCC if they are not operating
    > > at the power they are licensed for. It has to be logged on a set
    > > schedule and kept in the station's permanent files for the FCC field
    > > inspectors. If a station is operating below the level they are licensed
    > > for, they are not serving the area they agreed to provide service to.
    > > VERY few stations were ever allowed to differ from their rated power.
    > > The only two I ever saw were on military bases where the transmitter
    > > power was listed, with "Or as deemed necessary". These were in remote
    > > locations and major repairs were consider as 'Depot Level' repairs.
    > > Reduced or increased power was allowed, to stay on the air, but none of
    > > these were high power stations. The license was deemed a 'Courtesy
    > > License' by the FCC, which meant that they had little authority over a
    > > military transmitter, but the 'Courtesy License' was granted to make
    > > sure the frequency coordinators didn't assign a civilian station an
    > > allocation that would interfere.
    > >
    > >
    > > If your power level is too high, you can cause problems for other
    > > stations, and if it's too low, your advertisers will demand refunds.
    > >
    > > I was a broadcast engineer at one military and two civilian TV
    > > stations over a 17 year period. I lost count of the AM radio stations I
    > > did work for, or located parts and equipment to keep on the air.

    >
    > At least at one time, a station's backup transmitter could have lower
    > power than it's main, and anything went if it was the only way to put a
    > station on the air at all. Nobody liked it, but it was considered better
    > than dead air.



    Sure, but the backup was only intended for emergency operations. Some
    AM stations operated at reduced power at night, so the secondary
    transmitter shared both functions.

    BTW, have you ever seen the pictures of the WLW 500 KW 700 KHz
    transmitter in Cincinnati, Ohio? It also has one of the few remaining
    Blaw Knox diamond towers.


    http://hawkins.pair.com/wlw.shtml

    I saw that transmitter around 1970, along with the bethany Ohio Voice
    of America radio facility that was just down the road. The VOA station
    is gone, torn down and turned into yet another golf course. It had
    the original WWII Crosley transmitters when i toured it. The were being
    replaced by custom designed transmitters built by National. They would
    operate from the AM broadcast band, to 30 MHz, at any frequency in that
    range. All of the transmitters were 50 KW, and could be run singly, in
    pairs or whatever configuration they wanted. There was a huge, high
    gain curtain antenna strung between three towers that fired East-West to
    transmit to people behind the iron curtain. It would handle up to 500
    kW from the ten transmitters one anything from one to ten frequencies at
    once. I wasn't allowed to take any pictures, because it was a US
    Government facility, and the military guards searched us for cameras
    before we were allowed through the gates.

    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida

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