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  1. #1
    John Bartley
    Guest
    I'm starting to suspect RFI from a micro-cell in the overhead next to a
    PA system. Randomly (sometimes 2x/day, sometimes none), a digital sound
    reinforcement system overmodulates and gives "sewerpipe" sound for
    around 12 seconds, then returns to normal.

    Changes amps, changed mikes, still occurs.

    Know there's an ATT Wireless (now Cingular) base station ('micro-cell')
    within 20' of the sound rack.. in the drop-ceiling of the floor below.
    I'm beginning to have dark thoughts about RF hitting a cold solder
    joint in a wiring run and the demodulated result overdriving the
    digital sound system.

    What's peak power of a micro-cell? What would cause it to transmit at
    significant power for 10 to 12 seconds, and then not, for at least a
    couple of hours?

    Thank you for your kind and on-topic replies.




    See More: Power of a 'microcell' base station in an overhead drop ceiling?




  2. #2
    Henry Cabot Henhouse III
    Guest

    Re: Power of a 'microcell' base station in an overhead drop ceiling?

    We have a rack of TV modulators and ATSC receivers for our SMATV system,
    that started to act up after Cingular upgraded the power and antenna arrays
    on our roof above the rack. We had to relocate the rack and recable, which
    they paid for.

    It's a lot of power at 2.4 ghz!





    "John Bartley" <[email protected]> wrote in message
    news:[email protected]
    > I'm starting to suspect RFI from a micro-cell in the overhead next to a
    > PA system. Randomly (sometimes 2x/day, sometimes none), a digital sound
    > reinforcement system overmodulates and gives "sewerpipe" sound for
    > around 12 seconds, then returns to normal.
    >
    > Changes amps, changed mikes, still occurs.
    >
    > Know there's an ATT Wireless (now Cingular) base station ('micro-cell')
    > within 20' of the sound rack.. in the drop-ceiling of the floor below.
    > I'm beginning to have dark thoughts about RF hitting a cold solder
    > joint in a wiring run and the demodulated result overdriving the
    > digital sound system.
    >
    > What's peak power of a micro-cell? What would cause it to transmit at
    > significant power for 10 to 12 seconds, and then not, for at least a
    > couple of hours?
    >
    > Thank you for your kind and on-topic replies.
    >






  3. #3
    DecaturTxCowboy
    Guest

    Re: Power of a 'microcell' base station in an overhead drop ceiling?

    John Bartley wrote:
    > I'm starting to suspect RFI from a micro-cell in the overhead next to a
    > PA system. Randomly (sometimes 2x/day, sometimes none), a digital sound
    > reinforcement system overmodulates and gives "sewerpipe" sound for
    > around 12 seconds, then returns to normal.
    >
    > I'm beginning to have dark thoughts about RF hitting a cold solder
    > joint in a wiring run and the demodulated result overdriving the
    > digital sound system.


    GSM cellular systems are notorious for spitting out RF that is easily
    picked up by audio components. Usually its a short 2 or 3 second burst
    of what might sound to a laymen as high speed Morse code (as opposed to
    to white noise or the screech of a telephone modem you hear when while
    making a dial up connection) perhaps once every few hours.

    It comes over my laptop's speakers if my phone is within an inch of the
    laptop, within a foot of my radio alarm clock on the night table, within
    two feet of my desktop computer's external speakers' amplifier.

    The micro-cell may be putting out higher power and longer duration and
    more often data bursts.

    Not likely a cold solder joint per se that functions as a demodulator
    for a nearby AM broadcast band transmitter, but could be along the lines
    of "miscellaneous metallic junction intermodulation" (a common phrase
    used in the two-way communications industry) which *does* affect FM
    two-way radio communication systems.



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