Antenna Swap?

4 posts by 3 authors in: Forums > CWNA - Enterprise Wi-Fi Admin
Last Post: November 4, 2005:
  • I am prepping for CWNA.
    ...According to the Study guide, the Fresnel Zone is not influenced by antenna size or shape. Only distance and freq.

    How about your downtown and you want to create a PTP link between 2 shorter buildings and you are shooting the link down a street which has taller buildings on both sides. You install semi-directional antennas and the link fails.

    Is the better option to install highly directional antennas such as a parabolic dish (makes sense to me) or mount the original antennas on towers to clear the link above the other buildings?

  • Using a more focused (higher gain) antenna would not fix your problem in the scenario you described for the simple fact that distance and frequency are the only determining factors. Antenna gain is not part of the FZ size formula. You would have to mount the antennas high enough at each end so that there would be no obstructions in the FZ.


  • Thank you.

  • If I am understanding the problem correctly, then I would say that a more focused set of directional antennas would help in that situation. Setting the Fresnel zone aside, a more directional set of antennas will help reduce multipath because less signal will be bouncing off of other buildings thereby reducing or canceling the original signal. This is even if the final EIRP is the same when comparing the two antenna choices.

    I believe that in a P2P link a more focused beam is always desirable because of these reasons. The one downside that immediately comes to mind is that it can be more difficult to aim, but still not all that difficult.

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