Weirdest mystery problem

Discussion in 'Wireless & RF Design' started by Augmented7, Feb 5, 2015.

  1. Augmented7

    Thread Starter New Member

    Feb 5, 2015
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    Hi, I have 2 consumer wireless intercom boxes. That work perfectly under certain conditions. Hold that thought.

    I rent 2 adjacent shops in one building, each with it's own master AC master breaker box. When I plug-in the 2 intercoms in the same shop they work. Either shop (doesn't matter). But when I plug-in 1 intercom in each seperate shop they don't work. Here's where the mystery deepens...

    If I run a 10 meter extension cord from one shop to the other (thus essentially plugging the intercoms both into the same AC line). They work perfectly. (So it's not a distance issue, it's not an interference issue... heck, I even have line-of-sight through glass.)

    I'm clever, so I assumed maybe the 2 shop's circuits were out-of-phase... So I had my electrician reverse the incoming + and - to the main breaker. No luck!

    Hopefully someone here can help me solve this mystery and puzzle.

    I uploaded a photo of one of the intercoms, standing in the doorways of my 1st shop, looking at the 2nd shop.
    IMG_4063.JPG
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Simple. One intercom is plugged into a L1 120V circuit outlet, the other is plugged into a L2 circuit outlet. The RF carrier doesn't want to travel all the way to the pole pig and couple through the 240V center tapped winding on it...
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Yeah sounds like those communicate over the power lines. Each shop might be on a different leg of a 3 phase service for even load distribution. You might need to get one that uses radio communication.
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    We are saying the same thing. Those things wont even make it to the other side of the center tap on a given phase, let alone to a different phase entirely.
     
  5. Augmented7

    Thread Starter New Member

    Feb 5, 2015
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    Funny thing... they used to work fine, just recently they stopped working. What could have changed?
     
  6. Augmented7

    Thread Starter New Member

    Feb 5, 2015
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    Does it make any difference that the manufacture says it's a 4 channel FM transmitter/receiver?
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    that only tells you that it uses FM to transmit.
    misleading to be sure, but still true. It just transmits over AC wiring and not over the air.
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    So you've solved your problem: Connect an extension cord between the two shops.
     
  9. Augmented7

    Thread Starter New Member

    Feb 5, 2015
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    lol... that cord goes out one door and in the other... not too practical
     
  10. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    a small wire will do. extension cord needs to carry over 12 amps. If you can insure it will not be used as a power source for AC power tools and the like, then a small cable could be extended to get the intercom on the same circuit. maybe over head through the ceiling?
     
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