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A Does Microwave support only Line of sight communication LOS?

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  1. May 9, 2016 #1
    Hi there,
    Wifi uses either 2.5 GHZ band or 5 Ghz band and these bands lie in Microwave in EM spectrum. As i read in books, Microwaves are propagated using line of sight (LOS) technique, so sending and receiving antennas should need to be aligned accordingly. But WiFi signals are broadcasted, why? According to the rule WiFi needs to propagate signal using line of sight technique as its frequency lies under microwave spectrum.
     
  2. jcsd
  3. May 9, 2016 #2
    The alternative to broadcasting (i.e. omidirectional) is to use a directional antenna. Many WiFi bases have multiple antenna elements that can be adjusted to provide some modest directionality. Even so, the signal is easily blocked by soil, metal plates, plaster, rebar, dense foliage, etc.

    For example, let's connect the LANs of two distant buildings on a ranch using WiFi. We will need to use highly directional antennas at both ends of the link such as parabolic dish or eleven-element Yagi. (Each antenna are driven by WiFi routers.) You must still position both antenna so Line-of-Sight is acheived: raised above the foliage, avoiding a hill and metal barn.

    My former home has plaster walls backed by expanded metal lathe. I had to carefully place the WiFi router in the basement so reception occured through the wooden floor and doorways.
     
  4. May 9, 2016 #3

    davenn

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    Hi there
    welcome to PF :smile:

    it's not so much a technique ... LOS operations is something that comes with operating on microwave frequency bands
    the higher the frequency, the more important this becomes
    How LOS the path between the transmitter and receiver needs to be depends on a number of factors
    types of materials etc in the path, path distance, transmitter power, receiver sensitivity and types of antennas
    and coaxial cable feeds at each end to name a few
    for long paths 20km or more, then even eater vapour content in the atmosphere starts becoming important


    what do you mean why ?? ... doesn't really make sense

    again, it's not a technique, and I doubt you will find anything in the "rules" about such


    Dave
     
    Last edited: May 19, 2016
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