# Cable TV ground loop noise



## f0zz (Dec 1, 2011)

Hi all,

I decided to hook up my cable box to my AVR to watch the UFC PPV. But doing so added noise to the entire system. I know it's caused by my cable provider (RG6 wire). The two solutions I know about are to remove a ground tab from the cable box or the AVR units power cables or to use an isolator. Neither my AVR or my cable box have ground pins, so it appears my only solution is to purchase an isolator.

Is this really my only option?


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## TypeA (Aug 14, 2010)

Your cable box (the one mounted on the side of the house) should have its own ground separate from the house ground, did you verify this is so? Did you remove the rg6 from the cable box and touch it to something? Sometimes this will discharge any charge in the line, sometimes this charge will build back up quickly and sometimes it doesnt, but these two things are the first things I would be doing.


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## hjones4841 (Jan 21, 2009)

f0zz said:


> Hi all,
> 
> I decided to hook up my cable box to my AVR to watch the UFC PPV. But doing so added noise to the entire system. I know it's caused by my cable provider (RG6 wire). The two solutions I know about are to remove a ground tab from the cable box or the AVR units power cables or to use an isolator. Neither my AVR or my cable box have ground pins, so it appears my only solution is to purchase an isolator.
> 
> Is this really my only option?


If you have two 75 to 300 ohm matching transformers (baluns) you can make your own ground isolator. It is very easy: all you have to do is connect the 300 ohm (twin lead) sides together. One coax side to the cable, the other to the cable box. Works just fine.


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## lcaillo (May 2, 2006)

f0zz said:


> Hi all,
> 
> I decided to hook up my cable box to my AVR to watch the UFC PPV. But doing so added noise to the entire system. I know it's caused by my cable provider (RG6 wire). The two solutions I know about are to remove a ground tab from the cable box or the AVR units power cables or to use an isolator. Neither my AVR or my cable box have ground pins, so it appears my only solution is to purchase an isolator.
> 
> Is this really my only option?


No, this would be a patch, not a solution. The problem with ground loops with cable systems is almost always that the cable shield is not grounded to the electrical system ground electrode, or that the connections are corroded or loose. The cable should NOT have a separate ground. There should be a grounding block at or near the entry point to the home with a heavy gauge ground wire going to the electrical service ground. 

Measure the resistance between the cable shield while it is disconnected from your system and the ground on your electrical system. Measure for a.c. voltage as well. If there is more than a few ohms resistance you need a proper ground. If there is voltage from the chassis ground of the cable box to your electrical service ground, you have a bad cable box.


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## f0zz (Dec 1, 2011)

The cable coming into my house is not grounded at all. I'm sure it's grounded at the service pole outside my home, but there are no direct grounds after it enter my home.

All the cable is new. The connections are solid.


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## lcaillo (May 2, 2006)

Electrical codes in the US require a connection to the electrical service ground on all signal lines entering the home, at or near the entry point. The reason is to maintain a single point ground for all systems. This eliminates most ground current flow if the connections are good, conductors are sufficient, and the distances are not extremely long.


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## f0zz (Dec 1, 2011)

I decided to add my own ground connection to the cable. After adding the first ground connection at the point of entry (connected to a cold water pipe), noise was reduced by about 50%. 
I then added a copper cable between two splitters and the noise dropped to a very low level. Not sure why this helped, but it did.

I will add more perminant grou d in the near future.


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## wgmontgomery (Jun 9, 2011)

lcaillo said:


> No, this would be a patch, not a solution. The problem with ground loops with cable systems is almost always that the cable shield is not grounded to the electrical system ground electrode, or that the connections are corroded or loose. The cable should NOT have a separate ground. There should be a grounding block at or near the entry point to the home with a heavy gauge ground wire going to the electrical service ground.
> 
> Measure the resistance between the cable shield while it is disconnected from your system and the ground on your electrical system. Measure for a.c. voltage as well. If there is more than a few ohms resistance you need a proper ground. If there is voltage from the chassis ground of the cable box to your electrical service ground, you have a bad cable box.


+1


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## selden (Nov 15, 2009)

f0zz said:


> I decided to add my own ground connection to the cable. After adding the first ground connection at the point of entry (connected to a cold water pipe), noise was reduced by about 50%.
> I then added a copper cable between two splitters and the noise dropped to a very low level. Not sure why this helped, but it did.
> 
> I will add more perminant grou d in the near future.


You need to check with the bureaucrats\\\\\\\\\ people responsible for the "electrical code" in your area. Proper grounding is a safety feature to prevent fires and lethal voltages. Your local cable company probably has to be responsible for getting the grounding right.


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## TypeA (Aug 14, 2010)

The quality of your install may well depend on the quality of your installer also. Knology, who were fixing some internet stability problems for me, had mentioned the cable system should have its own separate ground and thats something lcaillo states is not accurate at all. Perhaps I misunderstood but Knology never did fix my problem so that makes me wonder if they just didnt have a clue even after several unsuccessful attempts to fix my issue. Glad you got it fixed fOzz


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## wgmontgomery (Jun 9, 2011)

TypeA said:


> The quality of your install may well depend on the quality of your installer also. Knology, who were fixing some internet stability problems for me, had mentioned the cable system should have its own separate ground and thats something lcaillo states is not accurate at all. Perhaps I misunderstood but Knology never did fix my problem so that makes me wonder if they just didnt have a clue even after several unsuccessful attempts to fix my issue. Glad you got it fixed fOzz


FWIW- when I did installs (dish, cable etc.) we were taught to ground everything to a single point. That may have been code for our area, but codes differ from city to city, state to state.  My info coincides with what Icallo stated, but perhaps code is different in your area?? :scratch:


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## lcaillo (May 2, 2006)

Codes vary with different jursidictions but they all generally start with the NEC. Some have additional requirements, but I don't know of any in the US that do not require single point grounding required by NEC. I believe that Canada is the same.

Anyone who insists that a cable or other signal should have a separate ground is simply mistaken. I have argued the point many times with installers. A call to the supervisor or, in the case of an intransigent manager, to the company risk management office will solve the problem.


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