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All FAQs → Cable Modems and Wiring Issues → 2. CATV Wiring

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Will old wiring in my house cause problems with the new wiring?

In other words, if a lot of noise is injected into an old wire, will the signal go through the splitter and get onto the new wire and cause problems?

This really depends on two things: The strength of the noise, and the isolation between ports in the splitter.

The isolation between ports means how much signal is blocked between ports. Most splitters will have between 15 to 25db isolation.

This means that if the noise on the wire is 15db, it won't really affect the other ports, but if it were like 70db or so, it probably would.

This is also why if you hook up a splitter wrong, the TV looks like crap.

Most people won't have this problem.

Thanks to Mike G. for this question.


Feedback received on this FAQ entry:
  • If your old wire from the ground block is feeding the main splitter(s) in the house, maybe into an attic or basement, then the answer to the question is YES, especially if its an old 59 cable or has kinks in it and so on...

    2008-12-06 04:12:35

  • Ok... This is the basics and it is somewhat Case specific. I live in a pretty large apartment building. I also used to work for a cable provider so have a bit more hands on knowledge. I use an amplifier on my cable internet connection and have for roughly 3 years now. There are some specifics in my case that very well may not apply to most. I am in a very large building (over 600 units total) (and thats just in my building which there 4 more 3 to 4 floors each depending). My amplifier is on the main incoming Coaxial. Then split on a three way splitter with my cable modem on the -3.5 connection TV's on the -7's. So that takes out a lot of the overhead interference. My cable modem works fine my internet connection work fine and I have used this setup for many years. So you can try it however, it will be a waste if there is not enough distance and splits between the modem and the amp. Also best to split the connection with the lowest negative number line straight to the modem. If you need more than 3 use a 2 way splitter then a 3-5 way splitter on the second coaxial out to the TV's (the lowest negative connection alway goes directly to the modem). Now if you don't have low incoming bandwidth this will not apply if you incoming is high and you amplify it, the splits then need to come after the amp. I would say negative seven straight to modem and negative 3.5 to -7 to another splitter for TV's. That should control the amperage slightly. However if you have high incoming bandwidth and/or there is another issue it will be a waste of money. You can also check the Coaxial wiring in your house, as sometimes pretty commonly your coaxial house wiring is old. This can be very specific as well in an older wiring scheme your splitters may not accept the bandwidth signal ratio your provider uses(This is VERY VERY common). Even if your splitters are good your Coaxial cable may be old. Or the line in may be old anywhere in between the line in within your house may have a single low bandwidth wire or splitter. These thing will definitely effect your connection. (case in point I once installed cable in a house tv and modem, but modem would lock I ran a new cable into the house to up the bandwidth, did'nt work new incoming splitter's amp and grounding, still did'nt work/new run into house to basement where modem was, no go found a single splitter in the roof under tile's in a small room in the basement which had a tan coaxial wire running to it and was also a low bandwidth splitter changed wire to the splitter and the splitter bam cable modem was locked when i got to computer room).

    2007-09-20 10:59:40 (rapid19 See Profile)



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by Raydr See Profile
last modified: 2002-05-12 12:12:43