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Poor television reception

Discussion in 'Electronic Repair' started by [email protected], Apr 1, 2005.

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  1. Guest

    A couple of months ago, I installed a new Terk TV38 antenna, an antenna
    rotator and new coax cables. But the reception is very poor for most
    of the channels, even when I rotate the antenna thru the entire 360
    degrees.

    All of the connections from the antenna to the TV are good.
    I've even run a new coax cable directly from the antenna to the TV.
    But the reception is still poor.

    (I have two TV sets and both get bad reception so the TVs are NOT the
    problem).

    My house is in Riverside, CA (about 60 miles east of Los Angeles).
    Almost all of the stations broadcast from transmitters on Mt. Wilson
    (49 miles northwest of my house).

    On a scale of "1" (extremely snowy picture and very garbled sound)
    to "10" (crystal-clear picture and sound), here are the
    "reception"-ratings for the channels I watch:

    Channel Rating
    2 3
    4 4
    5 3
    7 7
    9 8
    11 4
    13 6
    24 2
    28 7
    56 8
    58 8

    Any suggestions?
     
  2. Ken Weitzel

    Ken Weitzel Guest


    Hi...

    Wrong cable impedance? (59/75/300, etc)

    Don't know the antenna, but no balun at the head end?

    Ken
     
  3. Guest

    What is a "balun"?
    What is the "head end"?
     
  4. Ken Weitzel

    Ken Weitzel Guest


    Hi...

    Balun is silly talk for balanced/unbalanced... the little
    transformer that connects the 300 ohm antenna to the (hopefully)
    75 ohm coax.

    The head end is silly talk for the antenna proper...

    Ken
     
  5. Guest

    The antenna has a 300-ohm matching transformer to which is attached the
    75-ohm round coax cable.
     
  6. Art

    Art Guest

    Sounds like you need a better antennea with preamp installed professionally.
    A deep fringe antenna should do a work.
     
  7. Guest

    Hi, Art:

    According to the support-people at Terk (the manufacturer of the
    antenna) "The TV38 is more than enough antenna for where you are".

    The coax cable runs from the antenna to an antenna amplifier (about 20'
    away) then out to the TV.

    Gary
     
  8. Mark

    Mark Guest

    are there hills or mountains in the 50 mile path to Mt Wilson?

    what kind of reception do your neighbors get and what kind of ant are
    they using?

    what kind of reception do you get with the rabbit ears?

    How is your FM radio reception from Mt Wilson in the car or at home?

    Mark
     
  9. Deke

    Deke Guest

    First, replace the 300-ohm transformer. Half of the baluns that come in
    antenna kits these days are bad (Channel Master, Jerrold, Winegard...rotten
    quality baluns)
    Second, bypass the amp. If signal/picture improves, the amp is toast. You
    can get 75 0hm barrels at Rat Shack, or any electropnics store.
    Third, if you wired the cabling up, make sure you havent shorted out the
    coax connector. Check all coax connectors. LOOK CLOSELY! One tiny strand
    of wire, between the center (copper) conductor, and the wire mesh shield,
    and its toast, and everything goes to hell. If someone else wired it up, or
    you bought it refab, check the connectors anyway.
    Fourth, if you have a small, portable television, and a long extension cord,
    take it up and hook it directly to the antenna, and see how much snow you
    have.
    Fifth, how is the cabling run? Has some moron put a staple thru it?
    Staples will not only kill your signal, but they could short out the power
    to the amp, and blow up the power supply.
    Sixth, is the amp a two piece unit? If so, is the power supply, usually
    down in the house, plugged in?
    Seventh, take the Terk back, and buy a real antenna.
     
  10. Guest

  11. Franc Zabkar

    Franc Zabkar Guest

    The best location for a masthead amp is on the mast. ;-)


    - Franc Zabkar
     
  12. NSM

    NSM Guest

    How much do you lose in 20' though?
     
  13. Franc Zabkar

    Franc Zabkar Guest

    http://www.epanorama.net/documents/video/videocoax.html

    Attenuation data for RG-59 B/U:

    MHz dB/100 feet
    ----- -----------
    1 .6
    10 1.1
    50 2.4
    100 3.4
    200 4.9
    400 7.0
    700 9.7
    900 11.1
    1000 12.0

    At 500MHz the attenuation is about 8dB/100'. Over 20' there would be a
    1.6dB loss. This doesn't sound like much, but in my case a 3dB loss
    means the difference between an excellent picture and an unwatchable
    one. This 3dB loss results when I try to add a second TV to an
    unamplified antenna feed via a 2-way splitter.

    In any case, the question has to be asked, if the loss is
    insignificant, then why aren't all antenna amps installed behind the
    TV, or under the roof away from the weather?


    - Franc Zabkar
     
  14. NSM

    NSM Guest

    Cos you're in Oz mate, not in the US. Sometimes people have to put the
    antenna on a mountain 2000 feet away. Other times you have to snake cable
    down 300 feet of wiring closet in some building. You have to choose the way
    to do the job.
     
  15. Guest

    You can cut those losses in half with Belden 1694.
    Freq MHz loss dB/100'
    1 0.24
    3.58 0.45
    5 0.54
    10 0.72
    100 1.84
    540 4.25
    750 5.00
    1000 5.89
    1500 7.33
    2000 8.57
    2250 9.14
    3000 10.67
    This is a partial copy from the Belden catalog.

    If there are no mountains blocking the line of sight path, 50 miles
    shouldn't be a problem for a good antenna. Personally I'm partial to
    Winegard units. For 50 miles I'd use an amplifier directly on the
    biggest antenna I can install/afford to boost before the cable losses.
    The 1694 was the lowest loss cable I found in RG-6 size. I use it for
    my OTA HDTV. I'm only 35 miles out so I can use the SquareShooter (DTV
    is all UHF in LA).
    GG
     
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