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Re: [HDTV-in-SFbay] Digital signal update-Sutro & KQET

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  • Kevin Diggs
    ... !???!?!?? I seem to recall you mentioning in some earlier post that KCSM is running at 250 Kw? My signal meter / random number generators show KCSM at only
    Message 1 of 8 , Dec 20, 2007
      Don Hackler wrote:
      >
      >
      > The transmitter power level has very little effect on what signal level
      > is indicated on most consumer receivers. That is more of an indication
      > of signal quality rather than signal strength. As long as you have
      > enough signal to overcome the "cliff effect" the transmitter power is
      > not an issue.
      >
      !???!?!?? I seem to recall you mentioning in some earlier post that KCSM
      is running at 250 Kw? My signal meter / random number generators show
      KCSM at only a little lower than KGO-DT (~728 Kw?) and KPIX-DT (1000
      Kw). Do any of the stations' engineering personnel actually know how
      their ERP affects (effects?) their coverage area? And do they understand
      how environmental conditions affect their signal propagation well enough
      so they could modulate their power based on conditions? And would the
      FCC pitch a hissy fit if someone were to try this? Would it be true to
      say that beyond some point extra power does more harm than good by
      strengthening reflections from various obstacles? Enquiring mind wants
      to know. (according to Linux look `enquiring' is correct - don't know
      what Mozilla is whining about?)

      Back a few years ago something exploded in KGO-DT's transmitter /
      antenna shortly before the Orange bowl (thus cruelly forcing me to watch
      a hideous mess via NTSC). Before the next bowl game they managed to use
      duct tape, chicken wire, and bubble gum wrappers to get their digital
      setup back up. But if I understand they were sending half power into
      half an antenna for a total of 25%? The remaining bowl games looked fine
      (South San Jose 95123). Only a few breakups. Signal meters were like 2/3
      of normal. And I'm pretty sure this was with the Radio Shack
      omni-directional "2x4" antenna. Larry - do they know how this outage
      affected their coverage?

      Each stations digital antenna has four of those panel thingies, right?
      Does each one send out stuff in a certain direction? And thus requiring
      all four for uniform, full coverage (and thus condemning 50% of college
      viewers during that ill timed outage to suffer through NTSC?)?

      kevin

      >
    • Larry Kenney
      ... According to the latest info from the FCC, KCSM is running 536 Kw ERP, KGO is running 561 Kw and KPIX is running 1000 Kw. ... They are required to do field
      Message 2 of 8 , Dec 20, 2007
        On Dec 20, 2007, at 1:01 PM, Kevin Diggs wrote:

        !???!?!?? I seem to recall you mentioning in some earlier post that KCSM 
        is running at 250 Kw? My signal meter / random number generators show 
        KCSM at only a little lower than KGO-DT (~728 Kw?) and KPIX-DT (1000 
        Kw).

        According to the latest info from the FCC, KCSM is running 536 Kw ERP, KGO is running 561 Kw and KPIX is running 1000 Kw.

        Do any of the stations' engineering personnel actually know how 
        their ERP affects (effects?) their coverage area?

        They are required to do field tests and keep accurate records of their signal coverage, so they know exactly what their coverage is.

        And do they understand how environmental conditions affect their signal
        propagation well enough so they could modulate their power based on
        conditions? And would the FCC pitch a hissy fit if someone were to try this?
        Would it be true to say that beyond some point extra power does more harm
        than good by strengthening reflections from various obstacles? Enquiring
        mind wants to know. (according to Linux look `enquiring' is correct - don't
        know what Mozilla is whining about?)

        Back a few years ago something exploded in KGO-DT's transmitter / 
        antenna shortly before the Orange bowl (thus cruelly forcing me to watch 
        a hideous mess via NTSC). Before the next bowl game they managed to use 
        duct tape, chicken wire, and bubble gum wrappers to get their digital 
        setup back up. But if I understand they were sending half power into 
        half an antenna for a total of 25%? The remaining bowl games looked fine 
        (South San Jose 95123). Only a few breakups. Signal meters were like 2/3 
        of normal. And I'm pretty sure this was with the Radio Shack 
        omni-directional "2x4" antenna. Larry - do they know how this outage 
        affected their coverage?

        Power levels are granted as part of the station's license to transmit, and each station is licensed for a specific power.  No, a station can't adjust its power for conditions.  They have to maintain their power within 80% to 110% of their licensed power and log the power levels at least every three hours.  Most stations do it hourly, on the hour, and most keep their power within 98 to 102 percent of their authorized level.  The FCC would have more than a "hissy fit" if a station didn't maintain their power within the prescribed limits... they'd fine the station!   

        A desired coverage area is determined by a station, the appropriate power to cover that area is applied for with the FCC, and a license is granted by the FCC specifying the station's power.  A station can apply to change their power level if they want to, but they can't do anything until the FCC approves it.

        The power levels for the digital stations were initially assigned so that the digital coverage would match the station's analog coverage.  That was using engineering data so how they matched in reality, I don't know.  Some stations have since requested and have been approved for increased power since the initial digital license was issued.  You can see the present authorized power on the page for each station at the FCC web site, as well as a map of their coverage area.  A link is provided to each station's FCC page from my digital channel list (http://www.choisser.com/sfonair.html) if you want to see the latest figures.  Make sure you're looking at the digital license, not the analog.  Click on "Service Contour Map" to see the proposed coverage.

        Something to note: Less power is needed on VHF than on UHF to cover the same area and less power is needed for digital than for analog to cover the same area.  The maximum power levels for digital are much lower than for analog.  Analog UHF stations can go as high as 5000 Kw ERP.  The maximum for digital UHF stations is 1000 Kw ERP.

        Here's a comparison of some actual power levels for VHF.  KGO analog has an ERP of 316 Kw.  When they move their digital operation to channel 7 their ERP will only be 21 Kw.  Coverage area is supposed to be the same.  We'll see!  KNTV analog has an ERP of 316 Kw and KNTV-DT runs 103 Kw.  We can already see how the coverage of their two signals compares.

        You asked if beyond some point does extra power do more harm than good.  It would be more of a case of diminishing returns.  Twice as much power doesn't give you twice the distance... it's exponential.  That's why KGO-DT was able to do so well, back when they had their antenna failure, with just 25% of their power ... sending half power to half their antenna, as you stated.  As long as a digital receiver gets enough signal to lock in, you get a perfect picture.  So while the signal might have been quite a bit weaker at your home, it was still strong enough to work pretty well and lock in a picture.  Someone further away that normally received the station would not have been able to under those conditions.

        I don't know if they determined what their coverage area was using the low level compared to the normal level.  They were just happy to have the transmitter on the air and were too busy trying to get things fixed and back to normal to think about coverage, so probably they didn't find out what it was.

        Each stations digital antenna has four of those panel thingies, right? 
        Does each one send out stuff in a certain direction? And thus requiring 
        all four for uniform, full coverage (and thus condemning 50% of college 
        viewers during that ill timed outage to suffer through NTSC?)?

        kevin

        I have no idea what the antennas look like, so I can't answer this question.

        I hope that helps answer your questions, Kevin, and informs the other readers as well.

        Larry
        SF


      • Ron Economos
        This site shows the transmit antenna patterns: http://www.2150.com/broadcast/default.asp Most of the Sutro stations have a deep null to the west. No sense in
        Message 3 of 8 , Dec 20, 2007
          This site shows the transmit antenna patterns:

          http://www.2150.com/broadcast/default.asp

          Most of the Sutro stations have a deep null to the
          west. No sense in wasting RF on the fishes.

          Ron

          Larry Kenney wrote:
          On Dec 20, 2007, at 1:01 PM, Kevin Diggs wrote:
          Each stations digital antenna has four of those panel thingies, right? 
          Does each one send out stuff in a certain direction? And thus requiring 
          all four for uniform, full coverage (and thus condemning 50% of college 
          viewers during that ill timed outage to suffer through NTSC?)?

          kevin

          I have no idea what the antennas look like, so I can't answer this question.

          I hope that helps answer your questions, Kevin, and informs the other readers as well.

          Larry
          SF


        • Phil Ross
          I m sure that they have a pretty good idea regarding ...how their ERP affects ... their coverage area... And ...how environmental conditions affect their
          Message 4 of 8 , Dec 20, 2007
            I'm sure that they have a pretty good idea regarding "...how their ERP affects ... their coverage area... And ...how environmental conditions affect their signal propagation"
             
            From the FCC......
             
             
            Licensee: KGO TELEVISION, INC.
              Service Designation: DT   Digital television station

              Channel: 24     530 - 536 MHz  Licensed
              File No.:   BLCDT-19981216KF     Facility ID number: 34470
              CDBS Application ID No.: 279063

               37° 45' 19.00" N Latitude             
              122° 27' 6.00 " W Longitude (NAD 27)   

              Polarization:Horizontal (H)
              Effective Radiated Power (ERP):561.kW ERP
              Antenna Height Above Average Terrain:437.meters HAAT -- Calculate HAAT
              Antenna Height Above Mean Sea Level:468.meters AMSL
              Antenna Height Above Ground Level:214.meters AGL
             
              TV Zone: 2
              Frequency Offset: 0 (zero)
             
               Directional           Antenna ID No.: 18964          Pattern Rotation: 90.00
               Antenna Make: DIE     Antenna Model: ODD980424KF
            Relative Field polar plot:
             
             Relative field values do not include any pattern rotation that may be indicated above.

                0° 0.930     60° 0.725     120° 0.779     180° 0.127     240° 0.768     300° 0.731     
            10° 0.874     70° 0.634     130° 0.675     190° 0.129     250° 0.827     310° 0.949     
            20° 0.749     80° 0.740     140° 0.530     200° 0.134     260° 0.827     320° 0.972     
            30° 0.792     90° 0.818     150° 0.306     210° 0.296     270° 0.817     330° 0.784     
            40° 0.974     100° 0.832     160° 0.133     220° 0.513     280° 0.751     340° 0.736     
            50° 0.950     110° 0.833     170° 0.131     230° 0.659     290° 0.646     350° 0.862    
             
             
             
            ----- Original Message -----
            Sent: Thursday, December 20, 2007 1:01 PM
            Subject: Re: [HDTV-in-SFbay] Digital signal update-Sutro & KQET

            Don Hackler wrote:
            >
            >
            > The transmitter power level has very little effect on what signal level
            > is indicated on most consumer receivers. That is more of an indication
            > of signal quality rather than signal strength. As long as you have
            > enough signal to overcome the "cliff effect" the transmitter power is
            > not an issue.
            >
            !???!?!?? I seem to recall you mentioning in some earlier post that KCSM
            is running at 250 Kw? My signal meter / random number generators show
            KCSM at only a little lower than KGO-DT (~728 Kw?) and KPIX-DT (1000
            Kw). Do any of the stations' engineering personnel actually know how
            their ERP affects (effects?) their coverage area? And do they understand
            how environmental conditions affect their signal propagation well enough
            so they could modulate their power based on conditions? And would the
            FCC pitch a hissy fit if someone were to try this? Would it be true to
            say that beyond some point extra power does more harm than good by
            strengthening reflections from various obstacles? Enquiring mind wants
            to know. (according to Linux look `enquiring' is correct - don't know
            what Mozilla is whining about?)

            Back a few years ago something exploded in KGO-DT's transmitter /
            antenna shortly before the Orange bowl (thus cruelly forcing me to watch
            a hideous mess via NTSC). Before the next bowl game they managed to use
            duct tape, chicken wire, and bubble gum wrappers to get their digital
            setup back up. But if I understand they were sending half power into
            half an antenna for a total of 25%? The remaining bowl games looked fine
            (South San Jose 95123). Only a few breakups. Signal meters were like 2/3
            of normal. And I'm pretty sure this was with the Radio Shack
            omni-directional "2x4" antenna. Larry - do they know how this outage
            affected their coverage?

            Each stations digital antenna has four of those panel thingies, right?
            Does each one send out stuff in a certain direction? And thus requiring
            all four for uniform, full coverage (and thus condemning 50% of college
            viewers during that ill timed outage to suffer through NTSC?)?

            kevin

            >

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