How to be US FCC legal

  • How do I determine if my wireless systems are legal?  And, if I need to throttle them
    down, is reducing the Power in the pfSense gui to be lower than 99 a good method?
    I use both CM9's and some Atheros-based 400mW mini-pci cards.
    802.11g auto speed.  400-series coax (~3ft., and a few 12+ft.).
    I have various antennas: Omni's from 6 to 15 dbi.  Panels 8 to 18 dbi.  Parabolics 19 to 24 dbi.
    Some locations have Signal Filters with 2-3db insertion loss (this is bi-directional loss).
    And, a few Linksys WRT54GL (at default tx power) with 6dbi omni and 14db panel.
    I have read about a tip to turn off tx/autotx on the directional antenna to receive only.
    I also have a few Atheros-based 900MHz 700mW 802.11g mini-pci cards, are fcc limits the same for 900MHz as 2.4GHz?
    But, I don't yet know what steps I need to take.  Any words of wisdom, instruction, and/or educational links are appreciated.
    Also, Where may I find a value priced signal strength meter with N-Female coax connector?
    Thanks, -Pete.


    you can use any combination you want…..just will need to turn down the radio on the atheros card on the higher db antennas.

  • Great link!

    If my output is 26dbm, and I need to limit it to 24dbm, what would I set the Power to in the pfSense gui?  (100*24)/26 = 92  ?

    Thanks, -pc

  • If you need 24 db EIRP then you need to calculate your output, meaning radio output in mw - convert mw to db, subtract any insertion loss / connector loss / filter loss /spiltter loss /cable&pigtail loss etc. then add antenna gain.
    For the 400mw cards this will not be correct. they do not show output power in mw, but rather output power in mw +10dbi (astleast some do this). so mw to dbi +10dbi -"whateverloss" +antenna gain = dbi
    then you can do dbi to EIRP ( is a nice place for wireless calculators )

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