Here's a new one

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  #1  
Old 06-03-12, 08:36 PM
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Here's a new one

...at least to me.

My son has spent the last two weekends installing an invisible fence around the perimeter of his new property. He got it all laid out, tested, trenched in and tested again. Then he put the shocker collar on his dog and took him out to begin training him.

To his surprise, and his dog's pain, they discovered that the cable provider's coax feed had become part of the fence. That means that the run of coax, at least from the edge of the property to the house, acts as a piece of the fence. Approaching that coax shocks the dog in the same way that approaching the actual fence does.

Further investigation revealed that disconnecting the ground connection that the cable company made to the GEC also disconnected the induced connection between the fence and the cable. My son and his other Dad (his FIL) have a theory that the ground bond made the outer wrap of the coax act as an antenna, that the cable company failed to ground the cable at their tower, and that installing that second ground would nullify the antenna.

Further detail is that the invisible fence and the coax cross twice, at right angles and at a greater distance than the fence instructions specify.

My son is ready to call the cable people and ask them to send a tech out to investigate this with him. Any thoughts?
 
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  #2  
Old 06-03-12, 09:21 PM
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I am wondering if sleeveing either the coax or the fence wire in PVC where they cross would prevent the induction/receiving. OR maybe putting a barrier of wood/non-conductive material between the two cables.
 
  #3  
Old 06-04-12, 06:23 AM
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I am wondering if sleeveing either the coax or the fence wire in PVC where they cross would prevent the induction/receiving.
GMTA. Thanks, TI. We already talked about sleeving the coax - not the fence, 'cause we don't want to interrupt that, just prevent the cable from becoming part of it. Doing that would involve, at a minimum, digging up enough of the cable to get the sleeves on, even if we used something like cold-shrink. My son is unwilling to jump into that without first consulting with the provider about their two-month-old installation, and I understand that. Plus, it would involve digging for some distance onto his neighbor's property, since that's where his feed enters his property and the fence is installed along the property line.

Here's something that just occurred to me: what if the problem originates with the signal from the dog fence getting onto the grounding electrode, and then being transferred to the coax shield when that is connected to the GEC?
 
  #4  
Old 06-04-12, 07:57 PM
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Is the ivisible fence twisted around itself at the point where it leaves the house to the point where you want the invisible fence to begin? Than again, where the fence ends, and returns back to the house? From the point where the wire leaves the house, to the point where the fence both begins and ends, there should be two wires running parallel to each other. those wires have to be twisted around each other in order to cancel the signal and not shock the dog.
 
  #5  
Old 06-04-12, 09:25 PM
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From the point where the wire leaves the house, to the point where the fence both begins and ends, there should be two wires running parallel to each other. those wires have to be twisted around each other in order to cancel the signal and not shock the dog.
Thank you. That's a really solid suggestion.

Yes, the lead out and the return lead are twisted around each other and the field is cancelled out, according to both the testing and the dog's reaction.The problem is that the cable feed - the coax - becomes energized with the fence field iff the coax wrap is bonded to the GEC for the house. The coax takes a different path from the fence leads, so it is easy to see that that is the problem - besides the fact that disconnecting the coax-to-ground bond stops the problem.

Today, my son did these three things, and got these results:
  • He drove a new ground rod and grounded the coax on its own. Same result: Fence field on the coax when grounded; not on coax when not grounded;
  • He consulted with his neighbor, on the side where the cable enters his property, about his experience and his neighbor's experience with his own professionally installed invisible fence. They discovered that the neighbor has the same problem - but was previously unaware of it - and that each of their fences only energizes their own cable field. If bonded.
  • He called the cable company. No response yet.
 
  #6  
Old 06-04-12, 09:33 PM
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Puttning the fence power supply on an isolation transformer might help.
 
  #7  
Old 06-05-12, 10:55 AM
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Puttning the fence power supply on an isolation transformer might help.
Auger, that's not something I'm familiar with, but it sounds interesting. What is an isolation xfmr, how might that help, and where would one acquire one of those?

The fence came with its own xfmr, of course. It's a wall-wart, and I don't know the output specs, but I can find out.
 
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Old 06-05-12, 12:17 PM
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An isolation transformer is a two-winding (insulating) transformer with a 1:1 ratio. They are fairly common in shops servicing small appliances and electronics. They isolate the tested equipment from the neutral-ground bond in the service panel.

Unfortunately, I don't think this is your problem, especially since the unit already uses a wallwart for a power supply.
 
  #9  
Old 06-05-12, 12:43 PM
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I don't think this is your problem, especially since the unit already uses a wallwart for a power supply.
Thanks, Furd. That's what had me wondering too.
 
  #10  
Old 06-21-12, 09:27 PM
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It's resolved.

My son installed an isolation block between the coax ground and the house GEC. No more mid-yard shocks, and he's now turned the fence back up to "High."

Thanks for all of the great listening and tips.
 
  #11  
Old 06-21-12, 10:49 PM
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Thanks for the update.

........
 
  #12  
Old 06-22-12, 07:18 AM
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Good to know. Is the isolation block available at most stores or is it a online thing?
 
  #13  
Old 06-22-12, 11:53 AM
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Good to know. Is the isolation block available at most stores or is it a online thing?
I don't know -- yet! But I plan to find out, and come back to talk about it.
 
  #14  
Old 06-22-12, 08:39 PM
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No offense, but anyone who wants to use a shock collar on a dog should be required to wear it on their genitalia first ("turned up to high", of course) so they can feel what it's like. They are barbaric and should be outlawed. People use them simply because they are too lazy to properly train the dog. Not to mention they do nothing to keep out the real threats to the dog, such as other dogs/animals and thieves.
 
  #15  
Old 06-22-12, 08:43 PM
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No offense, but anyone who wants to use a shock collar on a dog should be required to wear it on their genitalia first ("turned up to high", of course) so they can feel what it's like.
Thank you for sharing .
 
  #16  
Old 06-23-12, 09:58 AM
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I'm an electrician and have a hobby farm. I know what it feels like, and it makes me not want to touch it again.
 
  #17  
Old 06-23-12, 09:43 PM
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Neither do I. Isn't that the point?
 

Last edited by Nashkat1; 06-23-12 at 10:04 PM.
  #18  
Old 06-23-12, 10:03 PM
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Clarification

I realize that when I posted this:
No more mid-yard shocks, and he's now turned the fence back up to "High,"
I didn't explain what the effect of turning the power to the fence up or down is.

For anyone not familiar with an invisible fence, turning the power to it up or down has no effect on the jolt the collar produces. The collar is battery-powered, and it does the same thing any time it's triggered.

Instead, the effect of turning the power up to "High" is to increase the range of the signal from the fence. Our best estimate is that the effective range of this fence can be varied from about 6", on Low, to roughly 8' on High.
 
  #19  
Old 06-24-12, 11:24 AM
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@ Jersey,
LOL!!! I hate to say it, but I agree!!! Just like having a dog collar and leash around a child!!!
 
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