Cable TV question, and advice requested. 1

[robertjo24]

I have a few questions about cable TV I was hoping you could help me out with.
1) What is the nominal signal level one should expect to see at their home from the cable company, (analog cable w/high speed internet)?
2) What is the nominal signal range an average cable ready TV will require to operate satisfactorily?
3) What is the nominal signal level required for a cable modem?

Here is why I ask.
A couple months ago, my high speed internet went out, (TV still worked). I did all the troubleshooting I know to do, and then called the cable company. The cable company technician said that the signal level to the house was sufficient, and that I had too many splits in the cable (one two way, then another one by the cable modem). He said this caused too much noise on the line and the cable modem would not sync. He removed my splitters, replaced a jumper cable to my modem, and installed one of his “higher quality” splitters. He also said that using low quality splitters and cables(like from Radio Shack or Wal-Mart) caused too much noise that would back feed to the main line and disrupt other users.
The internet feed went out again this week, and I expect much the same from the cable company tech, even though I left the configuration as he left it the last time.

I have been in telecom for a while now, doing everything from HF to satellite, teletype to gigabit networks, so I am not exactly ignorant. Does the cable tech’s response sound reasonable to you?

After he “fixes” the issue this time, I plan to run new direct feeds to all drops (3) in the house (existing drops are wired externally), and place a splitter/amplifier in the attic.

What should I watch out for to ensure I don’t cause myself, or anyone else problems on the line?

 

[softbatch]

I read that the expected signal strength should be 25dB where the cable originates. The whitepaper also pointed out that 8-15dB is ideal for each outlet in the house. Here are some good whitepapers:

http://www.atxnetworks.com/whitepapers.html

 

[softbatch]

I'm not sure if lowend splitters would be causing your internet to drop or not. I am currently in the process of running 8 drops for CATV in my house. I bought a Leviton 3x8 splitter from Home Depot which has a built in amplifier of up to 15dB. You can buy a $35 Leviton +25dB amplifier which may solve your problem.

Keep in mind, the amplifier needs to be placed before your 2-way splitters. Otherwise, you will amplify the noise as opposed to a solid signal. A few rules of thumb, a 2-way splitter causes approximately a 4dB loss in signal strength. A 3-way loses 6.5dB, a 4-way loses 8dB, and an 8-way loses 12dB.

Also, for every 100ft of RG6 cable, you will lose 4dB with your signal.

 

[robertjo24]

Great info.

I appreciate your input.