Expanding the FM band - Page 4
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Thread: Expanding the FM band

  1. #31
    Quote Originally Posted by DavidEduardo View Post


    There are a few that are viable, but in a very limited fashion. 1 kw at night above 1600 just won't cover a full Top 100 market, and daytime they are the equivalent of perhaps 100 watts at 550.
    I'm in North Carolina. I picked up one of those expanded AM band stations from Iowa at night.

  2. #32

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    Quote Originally Posted by vchimpanzee View Post
    I'm in North Carolina. I picked up one of those expanded AM band stations from Iowa at night.
    Many of the X-band stations are effectively clear-channels so at night they can do very well via skywave at night. Was it KCJJ?

  3. #33
    This has been discussed numerous times over the years, and a large expansion of the FM band simply isn't going to happen.

    The one thing that actually is feasible is to open up the use of 87.7 and 87.9 MHz to more than just analog Channel 6 TV stations pretending to be FM radio stations.

  4. #34
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    Quote Originally Posted by brettbutlerisok View Post
    Many of the X-band stations are effectively clear-channels so at night they can do very well via skywave at night. Was it KCJJ?
    The X-band is near-shortwave in nature, and stations on those channels skip nicely. Before the US opened up the band segment, I used to get a couple of 1 kw Argentine X-band stations quite easily, both in Miami and Puerto Rico.

    The problem is that night radio listening is low, few people want to hear a distant local AM station, and propagation is not consistent. Of course, there is no sales value in DX reception.
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  5. #35
    Quote Originally Posted by DavidEduardo View Post


    The X-band is near-shortwave in nature, and stations on those channels skip nicely.
    Where the X-band ends, the 160-meter amateur band begins, and trans-Atlantic communication (and reception on a standard communications receiver with a decent antenna -- even a portable with a whip if the noise floor is low enough) with 1 kilowatt (the legal maximum) or less is quite common at night.

  6. #36
    Quote Originally Posted by kevtronics View Post
    This has been discussed numerous times over the years, and a large expansion of the FM band simply isn't going to happen.

    The one thing that actually is feasible is to open up the use of 87.7 and 87.9 MHz to more than just analog Channel 6 TV stations pretending to be FM radio stations.
    If the FCC closes the Franken-FM loophole by eliminating analog TV on Channel 6, who gets the old analog Channel 6 frequencies?

  7. #37

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    TV stations.

  8. #38
    Quote Originally Posted by CTListener View Post
    If the FCC closes the Franken-FM loophole by eliminating analog TV on Channel 6, who gets the old analog Channel 6 frequencies?
    Digital television stations assigned to RF Channel 6. And nobody else.
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  9. #39
    Quote Originally Posted by DaveBayArea View Post
    Wow. I didn't realize the field strength was that different as you change frequency. So 10KW at 1640 = 100 watts at 550?
    I'm a bit late to the thread, but there's a very simple equation to calculate the change in field strength (in dB) at a given location for two frequencies, assuming ideal TX conditions and ignoring annoyances like noise floors and skywave:

    delta = 20 * log( f2 / f1 )

    The difference between 1700 and 550 calculated from that equation is just under 10dB, which is roughly 10x power, i.e. 10kW at 1700 will get the same coverage as 1kW at 550.

    David's rule of thumb is probably based on real-world observations - mine just comes from the early chapters of an RF textbook I halfway read years ago
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  10. #40

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    Quote Originally Posted by DaveBayArea View Post
    Wow.
    I didn't realize the field strength was that different as you change frequency.
    So 10KW at 1640 = 100 watts at 550?
    Dave B.
    It does across attenuating surfaces including land and fresh water.
    Surfaces such as seawater with several thousand millimohs
    (are these the right measurement units?)
    of conductivity treat the full band almost equally.

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