range calculation

Discussion in 'Cisco' started by herodot, Jan 27, 2005.

  1. herodot

    herodot Guest

    i ve a The Cisco Aironet 1200 Series(2.4 ghz) and my antenna is 12 dbi
    omni i want to buy amplifier 1 watt and 16 dbi amp2440 or amp2441 how
    can i calculate the extend area i mean how much km extend ?? (the
    formula"?)
     
    herodot, Jan 27, 2005
    #1
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  2. :i ve a The Cisco Aironet 1200 Series(2.4 ghz) and my antenna is 12 dbi
    :eek:mni i want to buy amplifier 1 watt and 16 dbi amp2440 or amp2441 how
    :can i calculate the extend area i mean how much km extend ??

    If you want to be able to extend to kilometers, then instead
    of buying an amplifier, you should buy a directional antenna.
    There are a few reasons for this:

    1) If you are in the USA, Canada, or urban Australia [and likely
    a bunch of other places] you are limited to 1 watt EIRP
    (effective radiated power). Thus if you were using the amplifier
    on what you transmit, then if you are in one of those jurisdictions
    you would have to turn down your transmitter power to 0 dbi.
    The restrictions in Europe are stricter; I do not recall the
    exact figures offhand, but you would probably have to turn
    down your transmitter to at least -9 dbi.

    2) Amplifiers amplify noise as well as signal. You want more of
    the signal to get through, not more noise. Directional antenna
    are good for getting more signal through.

    3) If your endpoints are fixed, then it is a waste of power to
    send the signal out in all directions as an omnidirectional antenna
    would: you just want to send to where your other endpoint is.
    If your endpoints are moving around, then an omnidirectional
    antenna might be suitable, but when your endpoints are moving around
    you have the likelyhood that they will move into areas that do
    not have a big enough line-of-sight to the base location. A simple
    laser-like glimpse of the base location is not good enough:
    for radio, you need a bigger clear pathway, known as a Freznel Zone
    [which has to do with the fact that radio bounces off objects as
    the waves spread out, and the bounced waves can have the effect
    of cancelling the original waves.]

    4) If you do want to get into long-distance mobile endpoints, then
    you are better dropping down in frequency such as to 900 MHz and
    a Motorola Canopy system. Lower frequencies are better at penetrating
    through obstructions such as buildings and leaves.
     
    Walter Roberson, Jan 27, 2005
    #2
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