View Poll Results: Will it work?

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Thread: UHF YAGI ... wrong location

  1. #1
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    Default UHF YAGI ... wrong location

    A few years ago the tower company installed a UHF RDE4412AE Yagi for our future use while replacing our VHF DB228. Now that we are ready to use such, they pointed it at the wrong tower.

    The transmit distance is 20.5mi with both Yagis approximately 75' up on the tower. The difference is approximately 30 degrees. I see where the widest beamwidth is 60 degrees around -10, but don't understand the correlation between the beamwidth and that number. Is this going to be an issue or gonna be all good?

    This is what I was able to find on the Yagis...
    Gain, dBi 12.1
    Beamwidth, Horizontal, degrees 60
    Beamwidth, Vertical, degrees 44.0
    Beam Tilt, degrees 0
    Front-to-Back Ratio at 180, dB 16



    Selection_004.pngSelection_006.png


  2. #2
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    And yes, I did try to find documentation on the 0 to -25 running down the middle, but was unable to find anything. Any docs would be much appreciated!!

  3. #3
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    The polar plot tells you that 30 deg off bore sight you'll loose 2 dB of gain. So your 12 dB antenna will work like a 10 dB antenna. Now assuming you're not using the antenna to place a null on an interfering signal I doubt you could tell the difference, 75' of cable could easily have the same loss.

    To properly answer your question would need things like TX output power, RX sensitivity, and path loss data but if it's more or less line of sight I don't think it will be an issue.
    It is a fine thing to be honest, but it is also very important to be right

  4. #4
    Will No Longer Registered

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    Is the yagi mounted for horizontal polarization?

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    A lot of users misread the directionality of a yagi antenna. The beam width usually only becomes critical if the two points are at the fringe of coverage. Although as a general rule you should point the antenna where you want to talk. Astro Spectra is correct the losses you will have should be wel lwithin the capture levels for your application, unless you need to climb the tower I see no reasone to mess with the antenns at this time.

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    Fun fact: the cmps_index.php page presents the poll without any context... I want to leave a snarky answer.

    This article explains radiation patterns okay:
    http://www.cisco.com/en/US/prod/coll...d806a1a3e.html

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    Agree. Unless you are trying to null something or its a really critical long path (in which case a 2db fade margin is unacceptable anyway) then it should not make any difference.

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    Thanks everyone for the great responses. I don't think we will spend the money to swing it around at this time.

    @Astro Spectra 40W, MOTO 1550LS receiver, approx 3.2dB, but it is LOS.

    @Will the elements are vertical