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RFI

Discussion in 'Security Alarms' started by Bob La Londe, Aug 8, 2004.

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  1. Bob La Londe

    Bob La Londe Guest

    I had a custoemr call on Friday. Their system started showing some RF
    devices dropping out of the system within seconds of their firing up a new
    wireless 802.11 network. I guess RFI detection works just fine with Napco.
    They shut down one of the computers on the network and the problem cleared
    right up. A quick test of several of the devices showed them working
    properly. Sounds like a noisy card on that one computer was generating RFI.

    Anway, atleast this one Napco system worked properly. The RFI problem
    showed up instantly, and reported properly as RF trouble, not fasle alarms.
    I also got accurate signal reporting that helped to pinpoint the problem at
    the central station.

    Sure its anecdotal, not statistical, but I am satisfied with this wireless
    system.
     
  2. Mark Leuck

    Mark Leuck Guest

    That almost sounds like something else, Napco RF operates at around 344mH
    but 802.11 runs at 2.4 ghz

    Good thing the customer didn't have crappy headphones :)
     
  3. anomynous

    anomynous Guest

    Now try it with the system armed, will it still report as a trouble or will
    it be a false alarm now?
     
  4. Bob La Londe

    Bob La Londe Guest

    I figured the same thing, except when one PC on the network was turned off
    the problem went away. I figure it was putting off some noise. For all I
    know it could be a grey market PC and it might be putting off all kinds of
    RF noise.
    --
    ** FREE Fishing Lures
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    ** www.YumaBassMan.com
     
  5. Jim Rojas

    Jim Rojas Guest

    It's probably the PC power supply, or the monitor that is putting out all
    the RFI.

    Jim Rojas
     
  6. Al Colombo

    Al Colombo Guest

    I think you may have hit the nail on the head when you pointed out the
    possibility that the PC might be causing RFI over a wide area of the
    spectrum. Although I'm not sure what connection this would have with
    the 802.11 wireless network, it is still a possibility. However, the
    fact that the problem did not show up until the 802.11 went into
    operation would make you wonder whether the wireless system might not
    be transmitting harmonics. If the computer is a home-brew rig, we know
    it probably did not go through a valid RF testing lab. I put a Napco
    system through a UL third-party testing lab in Glenview, Il. for one
    of my Work Bench Review stories, when I was with SDM in Chicagoland,
    and it passed with flying colors. It passed both for emissions and
    susceptibility. Of course, that was a hard-wired fire alarm system and
    not a RF-based burglar alarm.

    What did you do to solve the problem, or is it on going?

    Al


    --
    Allan B. Colombo, technical writer
    P.O. Box 30076
    East Canton, Ohio 44730
    USA
    Come and visit with me at
    www.securitymission.com
    www.tpromo.com
     
  7. Aegis

    Aegis Guest

    Hey Al... Just did 2+2 and realized you are THE Al Colombo... Cool!

    I'm taking my copy of SS&I to the shop tomorrow to show them your fire side
    chat article... Specifically the "Prime Contractors Advise Clients" part.
    Way too often, we've been backing down from the customer/GC and just
    "installing what they asked for" even when we KNOW it's not fully
    compliant... I mean the gray-area stuff; we won't do just anything under
    that umbrella. This shines a light on that gray area. Thank you for the
    great article.

    I was also reading tech talk with Bob Dolph... He came SOOO close to
    actually addressing the RFI/EMI issue (the one our Belgium yahoo is always
    screaming about). That little Zap Checker device has me curious.
     
  8. Al Colombo

    Al Colombo Guest

    Thanks for the kind words concerning my recent column in SSI. I have
    always looked at it in this manner, even before NFPA addressed this
    issue: "Who's the guy with the fire license? That's the guy that's
    going to take the hit if it's wrong."

    About the gray area, there really isn't a whole lot of gray stuff left
    in the area of fire alarm installations as NFPA has set the standard
    on just about every aspect of installation possible. No matter what
    we look at, there's a code to fit the issue.

    The problem that I am seeing in the field is that many installers
    don't even own a copy of NFPA 72, which is what almost all
    municipalities have based their fire codes on for decades. All of that
    is about to change as ICC gains acceptance at state level.

    A few days ago I stopped at a new home in the finishing stages to
    check out the rough-in so I could bid the thing for the homeowner.
    Guess what kind of wire the alarm dealer that roughed it used for the
    smoke detectors? If you said power-limited fire wire you would be
    wrong. They ran the cheapest telephone station wire that I've ever
    seen! Amazing. Oddly enough, every system he installs is like this,
    so how does he pass rough inspection? (Perhaps he knows someone?)

    About Bob Dolph's column this month, very good. I covered that RF
    sniffer some time ago. He does a great job writing his stories and I
    think this one was a good one. He's an extremely knowledgeable
    technician. I follow his column every month.

    I recall a story I wrote many years ago for AID or Security Sales (one
    and the same). This was when I wrote for them as a freelancer under
    the name of Carl Sloan. It dealt with eliminating false alarms due to
    RFI. My focus was on real life application, as it was the field I
    came from when I began writing full time for SDM in 1990 (since 1974,
    30 years total). Perhaps we'll have to dig that story out of mothballs
    and make it available on www.securitymission.com. It provided
    real-world solutions to RFI issues involiving hardwired systems. I'll
    let you know when it's up if you're interested.

    In any event, thanks for the great response. It's always nice to hear
    from one's readers and fellow alarm dealers. If you or anyone else has
    an idea or two for future feature stories or my Fire Side Chat column,
    please let me know. I can always use the help.

    Thanks,

    Al Colombo
     
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