Dog Fence Transmitting through Cable TV wire (bad)

Discussion in 'General Electronics Chat' started by isometric, Sep 21, 2014.

  1. isometric

    Thread Starter New Member

    Sep 21, 2014
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    I have a petsafe dog perimeter system (part number PIG00-10773), which I believe transmits at 10.65kHz through the wire buried in my back yard. The issues is that it seems that the transmitting wire (i.e. the perimeter wire) is transmitting the signal to the Cable TV wire, which cuts right through my yard shocking the dog in undesired locations. So along with the dog's confusion, I am left wondering if I need to reroute the Cable line or the transmitting wire -- both of which is more work than I would prefer to do. I have attempted to reduce the power of the fence transmitter to as low as it can go to minimize the signal pickup to the cable tv line. Another thought is to possibly purchase and apply a line filter to the cable tv wire on the PED, covering the 10.65kHz range, but I am not sure if that will make any difference.

    So over to the forum to get suggestions or ideas -- the dog and I thank you.
     
  2. sirch2

    Well-Known Member

    Jan 21, 2013
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    I start by looking at the points where the two wires cross, try to get more separation and check the the TV cable outer is grounded
     
  3. crutschow

    Expert

    Mar 14, 2008
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    Yes, try connecting the outer layer of the TV coax to ground using a copper ground rod driven into the ground. You can buy coax feed-through connectors with a ground lug for that purpose such as here.
     
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  4. #12

    Expert

    Nov 30, 2010
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    Gotta go with Crutschow. A (properly) shielded co-ax cable has no business allowing a signal to propagate along its shield and 10KHz is not an amazingly difficult frequency to control.
     
    Last edited: Sep 22, 2014
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
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    are the fence and cable tv cable both connected to the same ground rod?
     
  6. isometric

    Thread Starter New Member

    Sep 21, 2014
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    @alfacliff @#12 @crutschow Yes, the CATV line is connected to the same grounding rod as the fence transmitter. I unhooked the CATV ground line from the CATV box hanging on the side of my house and retested with the receiver collar-- unfortunately, I still have the same issue. I will pick up a new ground rod tomorrow and attempt to ground the CATV off of connection to the PED. (there is approx 200ft from the PED to the CATV box on the side of the house) If that does not solve the issue, I will relocate the transmitter wire per @sirch2 recommendation. Thanks, I will be sure to update everyone on my progress.
     
  7. Lundwall_Paul

    Member

    Oct 18, 2011
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    I have the same setup my dog fence is buried 4" down and runs directly under the overhead cable for the house. They actually come into the garage at the same place through the same hole. I don't have any problems like you mentioned but I took notes. I am using the Coax ground as Curtchow mentioned, and from the exit point of the house to where the fence wires leave to where it makes a loop around yard I twisted the wires to keep the pup from being zapped when she was near the house. My transmitter for the fence has no ground previsions. Other notes: When I purchased this house many years ago I noted that the ground rod for the panel was loose I flipped the main breaker and pulled out a 3 foot rod with very loose connections. Since then I replaced it.
    I hope some of this is a help.
     
  8. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I would leave the dog fence loop ungrounded. It seems to be a balanced loop, so grounding one end of the loop seriously unbalances it.

    Try to minimize the capacitive coupling where the coax crosses the dog loop. Make the coax cross the dog loop at right angles (avoid a parallel run).
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    is there a balun or transformer on the end of the coax, where it is connedted to the "balanced loop" if not, it is not balanced.,
     
  10. isometric

    Thread Starter New Member

    Sep 21, 2014
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    So I tried to ground the CATV from the PED tonight, but all I accomplished is to look pretty silly as my neighbors saw at me drive a rod into the ground. I discovered that there is some serious power coming though the coax end; as I touch it with my fingers, there is a noticeable tingle. Hooking the ground wire to the coax feed-through connector stops the tingle, leading me to believe I had established a proper ground. Testing the coax with the receiver collar resulted in the same, undesired result. Therefore, I think I am at where I started, needing to move the transmitter wire to what @MikeML suggests to attempt to cross the coax at a right angle and avoid a parallel run. I will report back if this solves the issue after the weekend, to where I will have the time to tackle that project. Again, thanks for all the suggestions.
     
  11. poopscoop

    Member

    Dec 12, 2012
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    I second the right angle approach as the most hopeful. Cross them at right angles and then ensure there's a 1+m separation along the rest of the run. I'm surprised grounding the outer jacket didn't solve the issue, and it is possible there is some impedance problem in the coax shield, bouncing the signal back along it's length. Any chance the cable has been crushed/cut/burned? Know any HAM's? This kind of thing is right up their alley, and they'll have the tools to test cable impedance.
     
  12. #12

    Expert

    Nov 30, 2010
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    I'm beginning to think the shield has been corroded to the point that you can't ground it properly.
    This is just so contrary to popular belief that I think it must be that, in this case, a wire is not really a wire or a shield is not really a shield.

    This is where I wish a good tech could be there. Somebody with a lot of experience and a gut feeling for how electricity works could probably find the problem in less than an hour.
     
  13. crutschow

    Expert

    Mar 14, 2008
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    Maybe we're looking at this from the wrong direction. :confused: If the TV cable is grounded at more than one spot then it could act like a loop and carry induced circulating currents which would then radiate the signal. Perhaps removing a ground would help.
     
  14. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Can you measure the 10.6 kHz signal in the coax? I thought those dog fences ran at low AM frequencies 455kHz?
     
  15. isometric

    Thread Starter New Member

    Sep 21, 2014
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    The cable is one of the thickest coax cables I have ever seen, installed only 2 years ago-- I doubt there is corrosion or a break in the shielding of the cable. What is interesting is that if I unhook the coax from the PED and leave the connection going into the house (and the ground connected at the house), the issue goes away and the receiver collar will not detect the signal over the coax.
     
  16. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Unhook the two ends of the dog loop from the transmitter. Measure the DC resistance between the two ends; should be a couple of Ohms (wire loop resistance).

    Measure between either end of the dog loop and the ground-rod under your building's electrical panel; should be infinite. If not, you have damaged the loop wire, and it is conducting to earth. That wire is supposed to be insulated...

    If the dog loop insulation is compromised, it would not be surprising to me if 10kHz current could take a short cut by flowing along the buried coax outer jacket.
     
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  17. crutschow

    Expert

    Mar 14, 2008
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    What is a PED in this context? A common definition is personal electronic device but that doesn't see to apply here. :confused:

    Your result may support my theory that it is a ground loop in the CATV coax is causing the pickup. In this case between a ground provided by the PED and the house ground connection.
     
  18. isometric

    Thread Starter New Member

    Sep 21, 2014
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    PED = PEDestal enclosure for telecommunications and catv.
     
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