Cable Spilter Question --5.7dB? --3.5dB?

Question

I need to spilt my cable 2 ways.I've noticed on the Monster 2-way spilters it says on the out: --3.5dB, and on the 3 way spilters --5.7dB? Can anyone tell me what this means? I would like to connect the spilter directly to the power strip "cable out" using a double male, or should the cable be spilt before it goes into the surge protector/power conditioner as it has 3 inputs/outputs?

Answer 1

It means how much signal is lost through the splitter.  Typically use the smaller number for high speed Internet if you have it because bandwidth is important for speed.  Or you can use the lower number for the primary or High definition TV.  -3.5 is less signal loss than -5.7  Good luck using the inputs and outputs on the power strip, I have found it interferes with some On-Demand and high def programming.  If your worried about the cable not being protected they do sell small DC blocks,  I have had luck with them.

Answer 2

The term dB, or decibels, is a logarithmic scale. When you split a signal in half, the loss you get on each output is -3.5 dB. So, if you feed the splitter with a 10 dBmV signal, you get 6.5 dBmV on each output. Most three-way splitters are really two ganged 2-way splitters, with the second splitter on the output of the first. So, you get outputs of -3.5 dB, -7.0 dB, and -7.0 dB.

Apparently, the splitter you have is a true 3-way split. So, the output for each leg is exactly 1/3 the signal input, or -5.7 dB per leg.

BTW - a TV or cable box input likes to see at least 0 dBmV at the input (higher is better, but at least 0 dBmV). When setting up a cable network, you can use the losses for the cable (about 6 dB per 100 ft for RG-6) and the splitters to ensure you have enough signal at the TV, depending on the signal you have to your house.

So, if you have 15 dBmV at the cable tap on the street  (standard) and a 100-foot drop, you have 6 dB of attenuation in that line for a signal level of 9 dBmV at the house. If you have two splitters (for a 4-way split, feeding four outlets), you have about 2 dBmV left to get through the house cable. That's only about 33 feet. So, you're likely going to need a 10 dB RF amp in line to feed all those cable outlets. Of course, that's at 1 GHz (high end of the spectrum, which has more loss per 100 feet). Still, an RF amp would be recommended in this case.

Also, an amplifier should be inserted as close as possible to the source. Otherwise, if the amp is at the TV, you're just amplifying the noise in the signal and you'll get a poor signal-to-noise ratio (snowy pictures with a good signal level).