Where to connect CATV ground breaker for amp AC hum? (1 Viewer)

[Kevin C Brown]

I have digital cable TV, and I have my cable line hooked up through an isolated path in my balanced power AC unit. It's worked fine for years. But recently, I've been having problems with losing integrity of the digital channels. My wife's line has been fine. So one conclusion is maybe something small has changed overall in the line, but because her line doesn't run through anything else and mine does, maybe that's why I'm having problems.

So I have one of these:

http://www.hometech.com/video/atten.html#XA-63400

And I've been wondering whether I should just connect it within my line, or before the splitter where it divides into mine and my wife's line. Take my AC box out of the loop for both.

Also, what's in one of these things? Sort of a high pass filter above 60 Hz or something?

And why would something like this be OK for cable and not for satellite? What's in a satellite signal that's different? (One sub-questions is: will this even work for a digital cable signal? That one I'll find out on my own... )

 

[John Garcia]

I put it at the wall where the cable comes in. I suppose it doesn't really matter too much where you put it in the line. It worked for me.

 

[Brian L]

I thought those things were simply 1:1 isolation transformers? As such, you get signal transfer, but no hardwired connection, and thus no potential for ground loops.

And I can't recall who makes it, but one of the hi-end boutique manufacturers makes a similar device, and its pretty pricey. Go figure!

I think the difference between sat and cable is that sat is grounded directly to your home elecrical system (well, it should be), whereas cable may be grounded somewhere else in their system.

BGL

 

[Chu Gai]

Frequencies are different. For well made, but pricey alternatives, look at Jensen Transformers and I believe they've got a toll free # and you can speak to some engineering types about further questions you've got. You might want to look at how your cable is grounded before it gets into the house Kevin. See if it attaches to the grounding rod outside by some means.

 

[Kevin C Brown]

Funny- I actually went outside and visually traced where the cable comes in the other day, but didn't even think to look for the ground...

OK, isolation transformer. I just didn't think they could do one that small. But that makes more sense. (I've got to think that that's what's inside my AC box too, but I'm running out of things to try to fix the problem. Like I said, was fine for years. I already swapped the cheapo splitter the cable company had installed, and that helped about 50%.)

Yeah, I've come across isolation transformers for as much as $120! (That Magic Box or something by Acurus, Aragon, Mondial Designs...)

 

[Brian L]

Absolutely.

Troubleshooting 101 says that if scenario A works, but B does not, find out what is different between A and B.

I wonder what really is within your AC box? Is it isolation, surge protection, etc.? A simple varistor that has failed?

Getting that sucker out of the loop would get your run and your wife's a lot closer to apples to apples.

BGL

 

[Kevin C Brown]

The only other difference is that I do have an additional splitter on my line. Allows me to watch one thing while taping another. I have a cheap one there, and also plan to upgrade that one too.

Troubleshooting 102 says: replace anything that might have failed or degraded over time.

When I replaced the cheapy splitter for the whole house, I found out that it was a 3-way splitter. One leg down 3.5 dB, and the other two down 7.0 dB. My line was on a 7.5 dB down leg. So I gained 3.5 dB when I went to a 2-way. Did help.

 

[Chu Gai]

The other thing I find useful Kevin, is to simple reterminate the connections to expose some fresh copper and then give them a good fingertight and a very, very slight turn of the wrench to insure a good connection. If one is a bit more anal about it, you can always pick up some of the Caig products (they used to, maybe still do, have a nice little assortment of things at their website) to treat the exposed wire before putting it into the splitter. A real long time ago, over in Tweaks I think, Bob Mc had somebody come in and give a real nice overview of splitting and other matters. Maybe if you ask him, he might recall what the link is and repost it.

 

[Brian L]

I guess I misunderstood the original problem...thought that your line was going through the Balanced Power unit, where as your wife's was not.

Glad you have improved the situation.

BGL

 

[Kevin C Brown]

Brian- Yes, that also.

Chu- You're making me think and I don't want to think. When the problem first started occurring, I jiggled a lot of the connections on my line. I seemed to get an "effect" that way. So I jiggled each one until I got the "noise" to go away. But it still comes back. I was actually thinking about cutting new ends for all the lines, but don't you need a ~$50 crimping tool to re-do all the coax connections right? So I figured I'm trying the cheapest/easiest solutions first... 'Course now I also know that it's not the main line into the house, just one of my cables... And most of my line are just purchased pre-determined length cables... The next thing to try. This is cool. I get to like 80% of the solution (or less! ) and you two are helping me out with the last percentage.

 

[Brian L]

You call yourself an HT enthusiast, and you don't own a crimper and a coax stripper??? Tisk, tisk, tisk

Don't over estimate the structural integrity of a coax connector! My old house had a weak cable signal even under the best conditions. Every six months I had the cable guys out to address a deteriorating picture. Seemed like all they ever did was re-terminate a connection at one place or another.

BGL

 

[Kevin C Brown]

When the problem first started happening, I swapped digital boxes with the cable company. Seemed to help for a while, but then came back. Yup, I need to think about those connections...

 

[chung_sotheby]

Are you sure that the isolation transformers and cable splitters you use have enough rated bandwidth? I had the same problem with ground loops, and I purchased something called a ground gaurd which got rid of almost all ground loop interference. I got this model instead of the Tributaries model specifically because it had higher rated bandwidth, and could therefore handle the new digital cable channels and on-demand programming. I also employ a cable splitter, and I had to purchase one that had higher bandwidth than a regular splitter.
I believe that for most digital cable, there has to be at least a 1GHZ badwidth rating for all the programming and features to function properly.

 

[Kevin C Brown]

I know that the splitters I have are rated for digital cable, but I do not know about the loop in my AC box or the gizmo from hometech. It's easy enough to switch between my AC box and the gizmo (which actually will remove one suspect cable from the equation too) to just test and see what the results are.

Chung- Do you know offhand the difference with satellite? I.e., when I go look at these products, a lot of them specifically say "not for use with a satellite dss system."

 

[Kevin C Brown]

OK, I finally had to rewire things, in that the problem got so bad I couldn't put up with it anymore.

Long story short, the problem was the CATV isolator in my AC conditioner. OK for analog cable, and even digital cable for a bunch of years. Maybe it degraded over time, or maybe there's something going on with the digital signal I'm getting now vs then. Did change the splitter (not much effect), and when I took the Equitech out of the loop, problem solved. Then when I put in the Hometech isolator, problem still solved. I just wish I had kind of gotten motivated a little earlier. I have 4 hrs of digital garbage from trying to tape Andromeda on the Sci Fi channel this week...

 

[Chu Gai]

Sometimes, stuff just dies and when it dies a slow death you don't notice it until it eventually becomes intolerable. I mean, it might've been that there was some sort of tarnishing inside due to atmospheric pollution and moisture. Couldn't happen in California though, could it?

 

[Kevin C Brown]

Maybe from the pollution here in the Bay Area.