Possible Power quality problems with cable company signal
Possible Power quality problems with cable company signal
(OP)
Recently A cable company ask use to do some power monitoring at a few of there subscribers houses. Apparently, their having trouble with the television picture tiling, or pixelating in these houses. They have tried everything they can think of. The company thought that it might be a power quality problem. I thought maybe ferrite cores on the coaxial cable might help. We are setting up a Hioki 3196 on the power lines coming into one of the houses to give us some insight into the problem. Does anyone have any possible solutions






RE: Possible Power quality problems with cable company signal
RE: Possible Power quality problems with cable company signal
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Possible Power quality problems with cable company signal
If that problem happening to all the cable customers associatted with the same transformer?
RE: Possible Power quality problems with cable company signal
Having said that, it is also true that a well-designed and well-maintained cable TV system should be relatively immune to such interference due to the shielding provided by the coaxial cable (and probably the fiber backbone).
A good way to check for RFI from primary distribution system is with a cheap portable AM radio. If you have a noisy insulator or similar, it will be all over the AM band, and the directionality of the ferrite antenna in the AM radio can help you track it down.
RE: Possible Power quality problems with cable company signal
RE: Possible Power quality problems with cable company signal
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Possible Power quality problems with cable company signal
RE: Possible Power quality problems with cable company signal
On the other hand, there are several factors that might affect your tv (see above comments), cable length for example, sharing your signal with other tv's in your house or wherever you are, maybe all is needed is a "signal booster" to get a better image. There are new types of tv's like the High Definition TV which might have higher image requirement than just the cable coming into a huose, anyways, hope this helps
Regards, be happy
RE: Possible Power quality problems with cable company signal
I have no idea what the cable company has already tried, if anything, but generally the first step is to determine if the problem is inside the building or outside. This can be done by connecting a TV directly to the cable just before it enters the building. If the signal has problems here, it is doubtful that it is a power quality issue. A small battery-powered TV could also help verify if problem is coming in on power lines. It could be RFI from another source using the power wiring as a means of getting in the the televisions. Cheap electronics are susceptible to RFI entering on the power lines. This is not a "power quality" issue because the RFI is not caused by the power system.
Who owns the cable wiring inside the apartment building? Crappy coax is a big source of problems, especially when installed by amateurs using the wrong tools and using cheap connecters.
A conduit that is "full of water" is a potential problem, although you can generally expect some moisture in an underground conduit.
RE: Possible Power quality problems with cable company signal
RE: Possible Power quality problems with cable company signal
I doubt that the currents would affect TV frequencies, but the cable may have been degraded by excess heat caused by circulating ground currents.
I think that this is a long shot, but you may want to suggest it in the interests of a complete power check.
You would want the cable companies approval to interupt service in any case.
If you are allowed to disconnect both ends of the cable you can megger it to check for excess leakage to ground.
As I said, it's a long shot and the cable people probably have tests and equipment to check cable quality, but if you ask power people, you will get power people suggestions.
Let us know how it turns out if you are able to.
Good luck.
respectfully
RE: Possible Power quality problems with cable company signal
RE: Possible Power quality problems with cable company signal
Obviously the pixelation only occurs with a digital signal, but wouldn’t some interference be measurable on the other televisions in the apartment.
RE: Possible Power quality problems with cable company signal
RE: Possible Power quality problems with cable company signal
Regarding "There is nothing in a power cable that can influence a TV signal" -- note that TV pictures update at 59.9Hz, about the same frequency as the 60Hz power line. Power problems in general and grounding problems in particular can "beat" against the 60Hz power signal. On an analog set, grounding problems will often manifest themselves as a line or band which slowly scrolls vertically across the TV screen. I'm not sure what the result would be with a digital tuner.... but it would seem that any small signal disturbance could result in pixelation....
Note that proper grounding of the TV cable is also required by NEC, but despite the code and picture quality issues, grounding is overlooked and misunderstood by many cable TV installers. Although I'd really suspect the cable TV signal level rather than power or grounding, I second the recommendation to check grounding -- check for clean connections, bright shiny copper and water pipe, tight bonding clamps, etc.
I'd recommend also posting your question at avsforum.com -- there's a couple sharp video engineer types lurking over there, just make sure you have a good BS filter in place for those AV-philes more inclined to the mystical than the technical.....
RE: Possible Power quality problems with cable company signal
Also, it's possible that the particular type of interference is more noticeable in digital mode than analog, althought that seems unusual.
Are the complaints clustered in a particular area of the building? Someone's computer could be putting out a lot of hash, coupled with a sub-optimal coax system. Is the problem intermittent at a particular time of day?
RE: Possible Power quality problems with cable company signal
I inspected the area where the main cable feed enters the building and attaches to the block that feeds each apartment. I could not find a connection to the building ground rod. I know this is a code violation. Perhaps it could be the cause of the problem?
RE: Possible Power quality problems with cable company signal
I like the noise source angle too. Often someone will hook their cable into a nasty noisy computer that will conduct stuff back to the cable.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Possible Power quality problems with cable company signal
RE: Possible Power quality problems with cable company signal
On audio equipment connected to the cable box, that noisy ground can manifest as a 60Hz hum. But even if it's not audible, it can still cause problems with the video reception too.
One quick test for grounding problems -- if you take one of those 2-prong receptacle adapters and use it to lift the ground on all of the AV equipment and all the problems dissapear, then it's almost definitely a grounding problem. Yes, that's a code violation and a safety hazard, so don't leave it that way.
Frankly, I'm shocked that the cable company wouldn't have checked that before hiring someone to check the power quality.
RE: Possible Power quality problems with cable company signal
Using automotive jumper cables to hook up the copper water line that came in from the well to the electrical service ground improved voltage regulation until I got back from the electrical supply house with a temporary neutral for Ohio Edison to hook up and some stuff to permanently bond the well pipe and casing to the electrical service.
Oh yeah, when I one time put in a new well pump for a female friend I found out ( before reapplying water pressure ) tha her ex-husband had installed some CPVC water pipe WITHOUT solvent cement. If I had not accidentally knocked a pipe joint loose I would have had a slapstick comedy as the new submersible pump would have provide more water pressure than the old jet pump.
And, a few weeks ago I found out that the reason why a gas furnace never really worked right was because there was a piece of foam rubber pipe insulation INSIDE the gas line!
Mike Cole
RE: Possible Power quality problems with cable company signal
A local car dealership (Hummers) was being remodeled. The plumbers disconnected a gas line; 1-1/2". Gas was coming out so they fixed this by stuffing in a rag. A few hours later.. The building shattered. I think there was even a fatality. I drove by a week later the walls that were still present were severely bulged glass surrounded the place. Stupid-incarnate.
So a missing cable ground? Sure.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Possible Power quality problems with cable company signal
Code DOES NOT require the sheild to be grounded at both ends.
Grounding a shield at both ends often introduces other issues. Sometimes these issues are serious.
Respectfully.
RE: Possible Power quality problems with cable company signal
Investigate what type of wiring runs throughout the building / houses: RG59, RG6, RG6 Quad Shield? I notice problems with digital cable and the lossy RG59. Finally, always use high quality, 1000 MHz DC PASSING splitters. Have you tried the comm. engineering forum?
Good Day.