atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring Cable TV issues

Good point. Terminating unused ports and connections is a rarely done practice on the low voltage side for some reason. Simply closing the system can solve numerous problems caused by ingress into the system. You certainly don't HURT anything by having it all properly terminated.

Yes Hal, I know they make proper test equipment. Also, there are splitters with open ports that should be terminated. This is one of those 'take a look at why it doesn't work' type of deals...there isn't a whole lot I can do, because the campus has their own cable TV people. Believe me, if it was up to me, I would re do the entire thing. My hands are pretty much tied in the matter.

EDIT
We got everything working. Bypassed the Amp and went straight out to the TVs. It all works fine now.
Jeff

Actually open splitter and tap ports happen all the time and not by mistake. Of course it's good practice to put terminators on unused ports but an unterminated port results from every jack not connected to something. When was the last time somebody put terminators on unused wall jacks? Even if you did they would never stay there.

Fact of the matter is the terminations (or lack of) will not affect the signal levels. Open ports can contribute to signal leakage which may get the cable company in trouble but that's about it.

Bypassed the Amp and went straight out to the TVs. It all works fine now.

Or so it seems. That amp musta been there for some reason don't you think? Like I said, TVs don't make very good signal level meters.

-Hal

However it's a place where outside interference can leak into the system.

Yes but that little bit is unlikely to cause any problems since the return carrier level has to be quite high.

Used to be that ingress was a big problem when it leaked into feeders and trunks. That problem has been eliminated with fiber.

-Hal

I had a situation like this happen (which is what makes me ensure terminated ends now).

Customers were retired seniors, she complained about noise bars in her TV all day and her husband had a hobby woodworking shop in the basement. He only worked in there during the day and the TV was fine at night.

I found a coax hanging in the shop (that was prewired for a wall mount set) was picking up the noise from the machinery. I screwed a female to female coupler and a 75 ohm terminator on, problem gone!

I also see this a lot on CCTV systems with unterminated loop backs and monitor outputs. Of course like Hal stated, the original carrier is weaker in this case so it doesn't take as much return ingress to cause noise.

When using terminators on amplifier ports, just make sure that the amplifier is NOT passing power through it, I terminated a long run one day and had forgotten to place the power plug in the correct position, I made the whole cable system snow. :shrug:

I finally realized what I had done when I went back to the terminator to make a test and burned the heck out of my fingers, those resistors can make quite a bit of heat!!

They do make power isolated terminators as well as splitters but yes, the correct way is to not power the output if it's not needed.

Twisted Pair- I think if you analyzed that situation you would have found problems such as low or marginal signal level and/or an abortion of cables and splitters. Something like that just can't happen when things are done correctly even with unterminated runs. This is why I stress test equipment and knowing what to look for. Judging proper operation with only a TV and no knowledge of proper design is not going to cut it.

I also see this a lot on CCTV systems with unterminated loops...

Different story, that's video and all loop through ends have to be terminated.

-Hal

Yeah I am still not sure what the problem is...the TV guy came today and gave us another amp to try. I put it in, and the signal was still horrible. Took the amp out, and it was fine.