What's the voltage on my cable?

[watdahel]

Here in Arizona Cox cable company installed a 12v 200mah amplifier/splitter at the entrance to the building. It has four terminals with 7.5 dB each. Without it I get snowy signal.

In New York, TimeWarner never installed an amplifier to the wire before entering the building.

My question is what's the normal voltage that flows through cable lines? Is the amplifier safe for my Plasma TVs tuner?

 

[Mrfrog840]

I believe its measured in Db not voltage if I'm correct. 120Db from the main line Im guessing?

Amp should be fine for your HDTV. Make sure you have some type of voltage regulator on your TV. I know where I live we get many brownouts.

 

[nullpointerus]

The Comcast cable tech. with which I recently spoke said +/- 10dB is fine.

Make sure the amplifier is grounded. The 12V part is the voltage of the amplifier's AC power source and should NOT be leaking into the cable lines if the unit is properly grounded.

 

[watdahel]

+/- 10dB on top of?

 

[watdahel]

Here's how my house is wired. The amp is remotely powered. Doesn't that look like the DC is going straight to my TV?

 

[nullpointerus]

+/- 10dB means positive or negative 10 dB. In other words, I'm talking about a range of 20dB:

{ -10dB, ... 0dB, ... +10dB }

As long as your signal (i.e. +7.5dB) fits in that range, you should be fine.

Originally posted by: erwin1978
Here's how my house is wired. The amp is remotely powered. Doesn't that look like the DC is going straight to my TV?

Maybe it looks that way, but that is not what is happening. The 3-way "grey box" in your diagram is actually a special remote power adapter, not an ordinary splitter. This special adapter sends DC power upstream to the amp and relays the cable signal downstream to the TV. No DC should be leaking into the line going to the TV.

 

[watdahel]

Why doesn't the DC power travel to the TV as well since it's the same wire it's travelling in?

 

[nullpointerus]

Because it's a remote power adapter, not a splitter. A splitter is just a "dumb" device that merely splits the same wire into two additional wires. A remote power adapter, on the other hand, has more complex circuitry capable of sending power upstream (to the amp) and relaying the TV signal downstream (to the TV).

Believe me, if you had DC coming into your TV through its cable jack, you'd know it. Even a little leakage current from a failing TV on the same line will distort the TV signal on the other jacks in very noticable ways. Pumping DC straight into the TV's cable-in jacks would probably kill a lot of stuff (immediately).