p-t-p wireless bridge

Discussion in 'Cisco' started by vespiacic, Jan 23, 2007.

  1. vespiacic

    vespiacic Guest

    I need to set up a p-t-p wireless bridge in 802.11g w/ Yagi antennas to
    cover a distance of 1.2 km.
    Line of sight is ok, but i'm worrying about fog. This land is always
    covered by an heavy cloud layer.
    Did someone experience such a problem?
     
    vespiacic, Jan 23, 2007
    #1
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  2. vespiacic

    Brian V Guest

    "vespiacic" <> wrote in message
    news:...
    >I need to set up a p-t-p wireless bridge in 802.11g w/ Yagi antennas to
    > cover a distance of 1.2 km.
    > Line of sight is ok, but i'm worrying about fog. This land is always
    > covered by an heavy cloud layer.
    > Did someone experience such a problem?
    >


    Yes, ran in to this a few years back, actually got bit in the ass by it
    big time. Had an install, did the proper site survey, ordered the equipment,
    installed it, everything went great.
    Get a call back from the customer saying the bridge was going down early
    AM and could not reach the remote site. Dispatched to site, got there,
    bridges were up, no issues found at all. Thought maybe possible power
    problems at one of the sites.
    Got a call back the next day saying the bridge went down again and that
    they didn't think it was a power issue. Again, dispatched to site, again, no
    issues found, bridges were up, running clean, show vers showed that they did
    not power down.
    Setup a monitoring station on the friday for simply pinging accross the
    bridge, let it run for the weekend, sure enough at about 330am thru 7am the
    bridges would go down, same exact thing on Sunday too, almost to the minute.
    Completely baffled at this point.
    Dispatched to site at 230a on Monday so I could see what the heck was
    going on. Monitoring the bridges I keep seeing the power levels drop and
    drop until finally no more link. Went up on the roof to check if anything
    was going on, could hardly see it was so foggy. Cranked up the power at the
    end I was on, drove to the remote side and did the same thing. At max power
    the bridges came back up, it was apparently enough to "break thru" the fog.
    It's a bad situation....at max power the noise levels are high when it's
    clear, at a lower power noise is great but breaks in the fog. Lots of
    experimenting and tuning brought us to about a 75% power level which is
    extremely high for the distance but gives them about a 98% reliability. It
    still does drop once in a blue moon during an excesivly foggy morning.
    Fortunately it occurs at a time when there is no one normally in the
    offices. Customer is happy, they know what causes it when it goes down. Not
    much we can do about it. They are saving huge $$ over the P2P they had.
    As a result of that project we have added a line in our "pre site survey
    form" that our customers fill out. "At any time of the day or evening is
    there a fog or any other weather anomily that you know of that may obstruct
    the view between the buildings."

    -Brian
     
    Brian V, Jan 23, 2007
    #2
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