Figuring my Ground Loop Out

Discussion in 'AV Receivers' started by Steve Young, Mar 9, 2004.

  1. Steve Young

    Steve Young Stunt Coordinator

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    I have been working on getting the ground loop hum out of my system for a couple of years now. It all started when I put my first amp (with a 3 prong plug) into my system. I then added a second amp (also with the 3 prong plug) for my subs. I then bought a Panamax MAX5100 hoping to fix my problem. In my system I have 2 satellite dishes so I could only run the antenna for one of them through the Panamax, because the other coax connection is for CATV. The only way I could get rid of the hum was to use cheater connectors on the amp cords, which isn't a good idea, seeing that I am an electrician and know the dangers of this. Well I did a test just the other day by hooking everything up normally and the hum was still there, which I expected. I removed the antenna connection going to the IRD that isn't connected through the Panamax and the hum disappears completely. Now what I am thinking is that all I need is another isolator for the other dish antenna cable. Does anyone know if there is such a thing for isolating a DBS cable on it's own, or do I have to buy another surge protector with the DBS protection built into it?

    Sorry to ramble on.
    Thanks for any help.

    Steve
     
  2. Chu Gai

    Chu Gai Lead Actor

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    Yes there is. Jensen transformers has a variety of products that'll do that with neglible insertion loss. You've got to pick the right one for the frequecies in question but then that's what toll free #'s are for.
     
  3. Mike Keith

    Mike Keith Second Unit

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  4. Steve Young

    Steve Young Stunt Coordinator

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    The problem is that the Sat uses a higher bandwidth, and the Panamax unit covers from 950Mhz to 2.2Ghz and 27V clamping. I guess I could always buy another smaller Panamax bar.

    Steve
     
  5. Wayne A. Pflughaupt

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    Steve,

    How is the grounding done on your antennas? If it’s going back to the electrical ground stake at the breaker panel, you shouldn’t have a ground loop problem.

    Regards,
    Wayne A. Pflughaupt
     
  6. Mike_Skeway

    Mike_Skeway Second Unit

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    I second what Wayne said.

    Make sure the ground for your cable/ant/sat/etc. is the same (or if it even is connected) as the rest of your electrical.

    When you disconnect it and the hum goes away, that is a good sign that it is not.
     
  7. Steve Young

    Steve Young Stunt Coordinator

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    Thx for the replies. I'm assuming when you say grounding of the antennas , you mean the shielding of the RG-6 coax?
    I think I used one of those grounding blocks and took the ground to the water pipe, but I am not sure if I did both dishes or not. If you think that that could be the problem, then I will make sure both shields are grounded back to the panel.

    Edit: I just checked and both cables are grounded using a cable block and grounded to a water pipe. I checked with my multimeter and there is continuity from the shielding (ground block) to the nearest receptacle ground.
    Steve
     
  8. Mike_Skeway

    Mike_Skeway Second Unit

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    Yes, make sure they are all connected to the same place, i.e., your cold water pipe or where your mains ground is.
     
  9. Wayne A. Pflughaupt

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    That’s to be expected, Steve, and it’s not a way to determine there’s not a problem. The problem is that if you grounded them to a water pipe, and your electrical is grounded to a ground stake, and the two of them aren’t connected somewhere, the electronics in your system have two paths to ground. That’s what causes a ground loop.

    Regards,
    Wayne A. Pflughaupt
     
  10. MikeTz

    MikeTz Stunt Coordinator

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    One note of caution. DBS (DIRECTV anyway) passes DC voltage along with signal down the coax so a transformer based isolator won't work with these systems. Panamax does make a DBS protector but I don't believe it's an isolator so it may not solve your ground loop.

    Best way to tame a humming DBS problem is to make sure the system is properly grounded (a single point ground bonded to your electrical service box). Most DBS hum comes from improperly grounded systems. A ground rod that is not bonded to the electrical service entrance can cause a hum. So can connecting the ground to a copper plumbing pipe.


    MT
     
  11. Jeff W.

    Jeff W. Stunt Coordinator

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