Discovered what "overdriving your tuner" looks like...

Discussion in 'Over the Air TV By RabbitEars.Info' started by comfortably_numb, Jun 3, 2019.

  1. comfortably_numb

    comfortably_numb Topic Starter Dogs have owners, cats have staff Pub Member / Supporter

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    I had been noticing complete intermittent signal loss on KCTV for the past few weeks. The signal would go from 80% quality down to 0 then jump right back up again. I thought it was a multipath issue; I realigned the attic antenna twice, the issue persisted. Then I decided to remove the 10 dB distro amp behind the TV and connect directly to the coax coming from a 3-way splitter located at the preamp power supply output. (The splitter and preamp power supply are located in a utility room, ~50-75 ft of coax away). Bingo! Problem disappeared immediately. Apparently, the distro amp was overkill.

    Just posting this in case anybody else ever experiences this issue :)
     
    #1 comfortably_numb, Jun 3, 2019
    Last edited: Jun 3, 2019
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  2. harshness

    harshness SatelliteGuys Master

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    DAs arguably shouldn't be used with less than a certain number of tuners (I'm thinking somewhere around 6-8 for the minimum -- dual tuner devices count as two).

    You really need to do the dB math to figure out what you need versus assuming that more dB is more better.

    Of course this is hard to assess unless you have a device capable of accurately reporting signal levels (consumer tuners do NOT count).
     
  3. primestar31

    primestar31 SatelliteGuys Master

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    That quality jumping up and down like that can also be caused by a radiating switching power supply. I had a Harbor Freight maintainer battery charger, AND a Dell laptop power brick both cause those issues a few years back. I permanently unplugged both of them.
     
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  4. Wireless Engineer

    Wireless Engineer SatelliteGuys Family

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    Using the LEAST amount of preamp gain SHOULD always be the goal.
    ......
    I always advise not using a preamp first to see if you are already getting every channel you want.
    ......
    Preamps with more than 12-15Db gain are merely going to increase interference levels and degrade the tuner's ability to reject it.
     
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  5. comfortably_numb

    comfortably_numb Topic Starter Dogs have owners, cats have staff Pub Member / Supporter

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    Wrong. I have to use the 30 dB setting on my CM-7777HD to achieve the best possible signal at my location (45 miles from the towers). I don't have issues with interference (except when I added the distro amp into the mix).
     
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  6. harshness

    harshness SatelliteGuys Master

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    Not wrong. WE's advice is generally sound but with things like TV reception, YMMV. I'm at 50 miles and I can pick up most of the market's stations with a UHF loop and rabbit ears.

    Sequestering your antenna indoors or mounting it too low to catch the passing signal demands that you make up for hiding it from the signal. Pointing your antenna well below the horizon also has an impact on how well it grabs the available signal.

    Putting an attenuator on a too-hot amplifier is a waste so one should work their way up rather than starting with a nuclear solution.
     
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  7. comfortably_numb

    comfortably_numb Topic Starter Dogs have owners, cats have staff Pub Member / Supporter

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    No preamp with an amplification of less than 20 dB has ever worked at my location, either with an inside or outside antenna. Sure, if you live 15 miles from the towers, you might not need a preamp at all. But once you go 30+ miles away, it all comes down to experimentation.
     
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  8. harshness

    harshness SatelliteGuys Master

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    Most antennas, when mounted as recommended, work just fine at their rated distances. Using a pre-amp because you don't want to mount an appropriate antenna at a sufficient height is a personal choice* and it is one that you have to spend a lot of time and money compensating for.

    * unless you're subject to C, C & Rs handed down on stone tablets from an HOA in which case, you're probably screwed
     
  9. comfortably_numb

    comfortably_numb Topic Starter Dogs have owners, cats have staff Pub Member / Supporter

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    The RCA ANT751R is rated for 60 miles. When mounted at the apex of the roof outside, it still would not reliably bring in most of my stations, even the ones that are 1000 kW. As we all know, "rated distances" as purported by the manufacturers are not often accurate.
     
  10. harshness

    harshness SatelliteGuys Master

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    The breakdown there is that they can pick up some stations at the rated distance (many seem to focus somewhere around channel 48) quite well but they stink elsewhere.

    Going forward, many "Digital Antennas" are going to be sucking wind because they don't cover the new band at all well.

    The old "Color TV" antennas of old are almost certainly going to perform better than many of the newer antennas because they focus on frequencies that we're actually going to be using after the repack.
     

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