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Strange bit of analog history

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  • Strange bit of analog history

    See page 58 on this link for a bizarre story out of the analog TV era.

    Analog TV involved separate video and audio signals. The analog TV transmitter was a single unit, usually with a single power supply and frequency-determining components. But much of the rest was separate for audio and video. The outputs of the two sides of the transmitter would then be combined in a "diplexer" and fed up a single feedline to a single antenna.

    Except... for one week in 1963 in South Carolina.

    WSPA-TV (ch. 7) held a permit to move from one mountain to another. One Sunday night, they shut down the visual transmitter and moved it to the new site, bringing it back on the air Monday morning. Leaving the aural transmitter behind (and operating) at the old site. They operated that way for a week -- with the picture transmitted from one mountain and the sound from a different one -- before moving the aural transmitter the subsequent Sunday.

    I have to think some strange things were heard on the TV sets of upstate South Carolina that week...
    Doug Smith W9WI
    Pleasant View, TN EM66
    http://www.w9wi.com

  • #2
    Found it, page 54 that's cool wonder just what it was like. How would they get it there, two STLs, one for video and another for audio?


    On page 56 it says WGN tried to test a 750kw signal! Any info on what happened with that? I know WLW was 500kw don't know for how long though.

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    • #3
      Oops.. I meant page 58 by the way the original magazine numbered it.. Adobe's impression of page numbers is different I wonder if there's a way to link into the middle of a PDF?

      STLs for analog TV stations generally used a subcarrier (same thing as the stereo MPX) for audio. I'm sure WSPA had separate STLs going to both mountains & just didn't bother to connect the aural STL output at the new site until the aural transmitter was installed.

      WGN never got approval to try 750kw. WLW's 500kw authority lasted from the beginning of 1934 until sometime in 1939. Initially the high-powered operation was experimental under the callsign W8XO, but they eventually received approval to operate the high-powered transmitter under the ordinary WLW calls. For much of the 500kw period, WLW was directional at night, with two towers. At the time, Toronto's CFRB was on 690 and complained of adjacent-channel interference.

      IMHO, what sunk superpower operation before World War II was fear on the part of smaller stations that they'd lose their network affiliations. In those days before TV, there were radio networks similar to the OTA TV networks we have today. (of course, there was no "cable radio" to compete with the OTA nets) Network stations in general were a LOT more successful than independents. A NBC affiliate in Columbus or Indianapolis or Fort Wayne or Louisville might fear that NBC would yank their affiliation to affiliate with WLW -- or that, even if the Louisville station kept its affiliation, many Louisville listeners would tune to WLW for network programs)

      As you saw there, stations continued to ask for superpower after the war. By then, TV had rendered the radio network pretty much obsolete. The problem for superpower was different. There was concern over "white areas" -- places where there was no radio service during the day. ("white areas", because someone took a black-on-white map of the U.S. and colored in the daytime coverage areas of existing stations. Areas not reached by a station didn't get colored in, and showed up white on the map) There were two ways to fix the "white area" problem. One was to increase the power of existing stations, the other to create new stations. Unfortunately, nobody was buying FM. (which could have solved most of the problem)

      The two solutions were mutually exclusive. Using 650KHz for a new station in Virginia would preclude a power increase at WSM -- allowing WSM to increase power to 500kw (even only during the day) would preclude use of 650KHz in Virginia. (even only during the day) (WSM won that specific round, the Virginia station in question ended up moved to 800KHz) Allowing WCCO Minneapolis to increase to 750kw might not displace the NYC daytimer on the same frequency, but it would mean the NYC station would never receive authority to operate at night.

      As you read the various old issues of Broadcasting on that site, you find that "a solution to the AM clear channel problem" was "just around the corner" for decades. The FCC never did really solve it.


      Stations of 500kw or more are not particularly unusual in other countries. There's at least one 2000kw station in Saudi Arabia. Ironically, the best-respected transmitters for this overseas superpower operation are made in Texas.
      Doug Smith W9WI
      Pleasant View, TN EM66
      http://www.w9wi.com

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      • #4
        If this works you can indeed link to a specific page in a PDF.
        Doug Smith W9WI
        Pleasant View, TN EM66
        http://www.w9wi.com

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        • #5
          I'll have to either change my internet settings or security settings or something related, as I cannot view the link, due to what could be incompatibility.

          Kegan
          My YouTube channel:
          https://www.youtube.com/channel/UCVG...VmF1EPlrZkiGAg

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          • #6
            The specific page link didn't work for me but I'm on an iPad...

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            • #7
              Loving the whole magazine! Thanks for posting

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