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E2000 Transmit Power Debate

Discussion in 'Tomato Firmware' started by Spyros, Apr 18, 2014.

  1. Spyros

    Spyros LI Guru Member

    I'm digging up this old matter of debate because after some searching im more confused than before.

    First of all

    E2000 has three antenna's

    2 x main antennas 1,5dBi

    1 x antenna 2.2dBi

    RF Power (EIRP) in dBm 17 dBm

    according to the Data Sheet

    and according to the Tech Specs

    Antenna Gain in dBi
    2.4 GHz:≤ 2 dBi
    5 GHz:≤ 5 dBi

    How Cisco calculates the gain and generaly how do we calculate the gain when we have antennas with different dBi and dual (2.4/5) frequency?

    Now let's come to DD-WRT wiki page

    The wiki advises to set 50mW because the EIRP rating is 17dBm but if we set to 50mW then we exceed the EIRP rating because

    50mW Transmit Power = 17dBm

    EIRP = Transmit Power + Gain - Cable/Connector loss

    EIRP of E2000 = 17dbm + 2dBi = 19dBm @ 2.4Ghz
    EIRP of E2000 = 17dBm + 5dBi = 22dBm @ 5Ghz


    we dont know loss but it should be minimal with 3 ufl connectors and a few cm of wire (0.1~0.3) just guessing. Anyway in both cases we exceed the EIRP rating of the device and i think that Wiki is wrong.

    The default value of E2000 @ 2.4Ghz should be 32mW/15dBm so that we match technical specs of the device.

    EIRP = 15dBm Tx Power + 2dBi Gain = 17dBm

    What do you think? Am i right or wrong?
    Anybody can estimate the Loss so that we can have a more accurate calculation? Anybody can calculate the Gain exactly based on three antennae? And final question....anybody knows the stock tx power value?
     

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