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Which direction for maximum signal on 3 antenna router?

  1. Jun 20, 2016 #1

    HRG

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    Purchased a Netgear R7000 Nighthawk router that has 3 antennas mounted on the back. Is the maximum signal strength in the direction formed by the plane of the 3 antennas (left to right) or perpendicular to that plane (front to back)?
     
  2. jcsd
  3. Jun 20, 2016 #2

    berkeman

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    Staff: Mentor

    The multiple antennas on a device like that are generally for spatial diversity (to help with multipath issues), not for use as an antenna array.

    http://core2.staticworld.net/images/article/2013/09/1253896_bk_1160-100055786-large.jpg
    1253896_bk_1160-100055786-large.jpg
     
  4. Jun 20, 2016 #3

    HRG

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  5. Jun 20, 2016 #4

    berkeman

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    Yes, in my experience they are used for spatial diversity (on receive the one antenna with the highest signal strength is picked and used, and on TX that same choice is used or the packets are sent on each antenna). I'm most familiar with embedded systems and the use of RF for packet transmission, so maybe the WiFi routers do something different. It would be good if a WiFi router expert would chime in. :smile:
     
  6. Jun 20, 2016 #5

    berkeman

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  7. Jun 21, 2016 #6

    HRG

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    Berkeman, thank you for your responses.

    Ah ha, I think I'm beginning to understand the role of multiple antennas on a router. Here's what I think I understand from the info you gave me. Please make corrections or comments as necessary.

    Assume the Netgear R7000 router that you posted a picture of. Netgear recommends that the center antenna be vertical and the two outboard antennas be set at 45 degrees.

    On transmit "from the router", probably only the center vertical antenna is initially used so the transmit pattern is circular. Depending on the number of re-transmits required, one of the outboard antennas may be used. Since the R7000 has beam forming technology, all 3 antennas may be used in diversity to achieve the best transmit directivity.

    On receive "by the router", the 3 antennas are used in diversity to get the best signal quality.

    Since the 3 antennas on a R7000 router are in the same plane, best diversity would be achieved perpendicular to that plane (front to back). Minimal diversity would be achieved parallel to that plane (left to right). So the best quality of transmit or receive signals would be perpendicular to the plane of the 3 antennas.

    For best omi-directional diversity, a router with antennas mounted on the sides and on the back would be optimal.

    Corrections or comments appreciated,
    HRG
     
  8. Jun 21, 2016 #7

    berkeman

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    I think that's mostly right. Multipath is a real problem with WiFi signals -- you get destructive interference with reflections, and you can also get polarization rotation (hence the 45 degree option for the outside antennas). :smile:
     
  9. Jun 21, 2016 #8

    HRG

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    Berkeman,

    Thank you for all of your invaluable help. I was totally lost on my first post but I think I understand how to set up routers with multiple antennas now.

    Have a great day,
    HRG
     
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