Circuit Breaker "On" with no connection

[templdl]

In a somewhat related story...

I know this sounds like a Dilbert cartoon, but it really happened. A friend of mine was an IT manager for a government entity. His nontechnical boss somehow got hold of the IP number list for all the computers in their department and complained about the gaps in the list. He made my friend change them so that the gaps were eliminated.

Anal anybody?

 

[GoldDigger]

Actually, I found a really neat alternative to splitters. It's an 8 channel bidirectional video distribution amp. I have it mounted in a closet with home runs to all my video drops. All the unused ports are terminated, as are any drops that aren't connected to a device. It works great; I have cable boxes on two of the drops and they talk back to the cable company through the amp for on demand programming.

Probably not as much use for over-the-air broadcast reception where the levels vary from channel to channel and the noise floor is important, but for cable with tightly (I hope) controlled levels it sounds ideal.

 

[cowboyjwc]

At the risk of being disrispectfull to my mother in law earlier in my life she always struggled with mental illness. On time she went around her house and sprayed all of the of the outlet with silver paint . In her mind or was to keep the evil from coming out.
Does it mean any thing that she liked me?

She didn't spray you with silver paint did she?

 

[ggunn]

Probably not as much use for over-the-air broadcast reception where the levels vary from channel to channel and the noise floor is important, but for cable with tightly (I hope) controlled levels it sounds ideal.

It is. I already had a conventional VDA installed, but when we (and by "we" I mean my wife) wanted to start getting on demand content from the cable box, that meant I had to patch around the VDA so that the box could talk back to the mother ship. A couple of years ensued of pulling cables through the house from the closet where the cable came in to wherever the cable box was.

In frustration one night I googled "bidirectional video amplifier" not knowing such an animal existed, and there it was! I ordered one, got rid of all the splitters, and ran home runs back to the closet for each drop.

And that's when I came to find out that cable TV termination is real; until I terminated all the open ports, the dialog between the cable boxes (I now have two of them) and the mother ship was very undependable, and some channels would not work at all.

 

[GoldDigger]

It is. I already had a conventional VDA installed, but when we (and by "we" I mean my wife) wanted to start getting on demand content from the cable box, that meant I had to patch around the VDA so that the box could talk back to the mother ship. A couple of years ensued of pulling cables through the house from the closet where the cable came in to wherever the cable box was.

In frustration one night I googled "bidirectional video amplifier" not knowing such an animal existed, and there it was! I ordered one, got rid of all the splitters, and ran home runs back to the closet for each drop.

And that's when I came to find out that cable TV termination is real; until I terminated all the open ports, the dialog between the cable boxes (I now have two of them) and the mother ship was very undependable, and some channels would not work at all.

The very wide frequency range used by cable with its large number of channels makes things very interesting. The simplest example of why you need to terminate is that if you have an open circuit at the end of a cable whose length is an odd multiple of 1/4 wavelength at some frequency, the apparent impedance at the other end of the cable, at that frequency, is a short circuit. That can really drag down the output to the other cables!

 

[ggunn]

The very wide frequency range used by cable with its large number of channels makes things very interesting. The simplest example of why you need to terminate is that if you have an open circuit at the end of a cable whose length is an odd multiple of 1/4 wavelength at some frequency, the apparent impedance at the other end of the cable, at that frequency, is a short circuit. That can really drag down the output to the other cables!

Yes; before I terminated all the open ports on the VDA and the ends of the drops that weren't connected to anything I had issues. The cable boxes would sometimes fail the handshake with the server in the sky, and some channels would either say "not available" or would just be black. The cable company came out a couple of times; the guy replaced cable ends and recommended I change the coax in the walls, neither of which had anything to do with the problem. In fairness, I had some variables in my system that he hadn't encountered before.

I did some looking on line, and I read about termination and the problems that lack of it can cause, so I bought a box of terminators and installed them everywhere I could. Problem solved.