Outside cable ground and hum bars--culprit?

[babyblues71]

Re: The Coaxial Cable ground wire (Via Brighthouse Networks)---is meter location important where the wire is placed? Ever since I bought a digital television, I have been seeing hum bars, which are, as I have gathered, indicative of a ground loop isolation problem. To test the theory I temporarily tried a 3 prong to 2 prong converter, plugged it into the AC outlet (And yes, I’ve tried other outlets), and the hum bars were gone. Knowing that’s not safe, I disconnected the converter, plugged the t.v. back in, and then built a temporary 75-300-75 balun device. However, I’m not entirely convinced that this is giving me the best signal level possible. Now, before I started fooling around with these temporary fixes, our cable person was out here trying to determine the problem (And he couldn’t figure it out, obviously). He even ran a direct line from the cable access panel on the house to the t.v. and the hum bars were still there. Well, anyway, while I was outside the other day, I noticed that the cable access box on our house was grounded right “above” the metal tubing that was going into the house “above” the dials of the electric meter and not below it. Would this possibly cause a problem? I mean, I realize that Jensen does offer a 60 dollar ground loop isolator that is supposed to be rather decent, but if it’s something as simple as repositioning an outside ground wire, I’d rather do that if you think that may be the problem. Help?

Brent

[cablewithaview]

Connecting to the tube? If you have a ground wire coming out of the meter to a ground rod, that should have been attached there below the meter base.
Not only should the tech bypassed with a new cable to make sure it wasn't bad, he should have disconnected the ground itself from within the box to determine if that was the cause. In some cases that I have had that problem, it's usually something in the house feeding back to ground or something out on the power end of it feeding back on the vertical. To resolve it, I either ground out on the pole to see if it goes away or leave it loose if I am convinced something in the house is feeding back to ground.
As for the isolator, I haven't never used one so I couldn't be of help there.

[babyblues71]

Hmmm...not entirely sure if I described the setup right or not. On the left of the electric meter, about a foot to a foot and a half away, is the coaxial cable access panel box. On the upper right portion of the back of the cable access panel box is a ground wire that is going up and to the right and connected via a bracket on the metal tube part that is located above the electric meter---it looks like the upper part of that metal tube is the part that supplies electricity to the house via internal wires, but I may be wrong. I just thought that, perhaps the ground wire, instead, should be a little longer and connect to a bracket on the metal tube part that is "below" the electric meter, thinking that the ground wire isn't close enough to ground and also that somehow the meter part might be causing interference or something. I suppose I could always try it if I can figure out how to undo the ground screw on the back of the coaxial cable box. I can barely get my fingers back there, and the box can't be opened unless I clipped this thin little padlock they have on the Bright House box. And I don't want to get in trouble doing that......the clamp that's connecting the ground wire above the electric meter wouldn't be a problem--that's just a bracket and a screw, but the length of the ground wire wouldn't reach where I needed it to go. Also, if I do find a way to test this, what gage of ground wire is usually considered better for this type of purpose?

Brent

[cablewithaview]

Na, you described it fine, I'm just saying the ground wire from the box should have gone straight to the ground wire coming out the bottom of the meter base to the ground rod. Usually you can use a #4 split bolt to tie the cable ground to the power ground coming out of the meter base. As I have said, it could be something feeding back from the house or the power company side of it.
BUT BE WARNED, LET PROFESSIONALS DO THE WORK, NOT YOU!!! There is nothing like having a 120 volt (or more) energized ground because of something bad wrong on either end.

[babyblues71]

Hmmm....interesting....I don't even recall seeing a ground wire coming out of the bottom of the meter box. I'll have to check it again tomorrow in the daylight. Is it possible they put it through the southern part of the tube and brought it out from the bottom? Also, just out of curiosity, if one were to disconnect the ground wire coming from the coaxial box or from the end that is hooked to the electric meter metal tubing via that bracket and the problem stopped, would that instantly pinpoint the coax's ground---as to "where" it's being grounded, as the primary problem? And would doing that, without touching any sort of ground wires from the meter box, present any potential problems for me? I'm not sure how much of a charge coax grounds could potentially carry if something were "wrong" with a powered amplifier or "whatever" they may have up on the telephone pole (They don't bury coax here in this part of Florida). The most difficult thing is getting these people out here. First of all, it's like pulling teeth. Second of all, if the problem doesn't go away, they will try to charge me. I suppose it's always possible that it's a ground interference problem between the coax and the Component video cables I have running through the wall to my TV, but since the technician brought in a line from outside and it did the same thing, I'm thinking it's more of an outside problem.

Brent

[cablewithaview]

Some older houses didn't have ground running from the meter base to a ground rod.
In this case, maybe installing an 8 ft. ground rod and the cable being grounded separate might cure the problem. (note warning mentioned before)
It can be an outside issue or even an inside issue as well. Just because a cable was run from the outside and bypassing the current wiring doesn't necessarily mean it is an outside issue.

[babyblues71]

Oh, the build is only a year old. However, our builders, including our electricians, apparently got their certifications as prizes via boxes of Cracker Jack. :) We're "still" fixing a lot of their mess-ups. Anyway, is it possible to attach pictures here without having to run them through an FTP site--aka our own URL's? If so, I might take a few digital pictures of the vicinity in case I come across a potential question that I may need to ask the electric company and/or cable company, but would like another opinion before I ask.

Brent

[cablewithaview]

Save pictures to your computer, then when you post a reply, there is a "manage attachments" button below that allows you to upload those pictures from your computer. :alienmorph:

[babyblues71]

Ah--I see the button now. Thanks for all of your help!

[Jonathan Kramer]

I just logged on and have read through the thread. Interesting, to say the the least.

With a ground loop like you're describing, and with the counsel that Jody's already offered, it's clear that the grounding is an issue (but may not the only issue).

Grounding to what's called the meter riser (from the meter to the service head above the roof) is one of the permitted locations, but perhaps not the best in some rare cases.

The fact that you could isolate the ground to clear the bars suggests that, indeed, there is a ground loop. A loop may be caused by inadequate bonding to the meter electrical by the house electrical ground. When you connect the grounded cable TV drop, current flows on the shield seeking ground, which will be outside your home. If you have flickering lights, or occasional noises from your refrigerator, its quite likely that the electrical grounding is suspect.

This is a potentially (no pun intended) dangerous situation. I don't suggest a isolation transformer. It only masks the issue.

Get yourself a qualified/licensed electrician NOW to look at the house ground, and the cable TV ground, to make sure that (1) the house ground is really at ground potential, and (2) that the cable grounding bond is electrically connected.

jlk