Most cable systems are designed to provide 15-20dBmV at the tap, which
equates to about 10-15dBmV at the groundblock. For safety's sake, use
the lower number in your calculations.

As you've seen and others have written, a 4-way splitter loses ~7dB on
each leg. The actual loss varies with the frequency. The 7dB is at
50MHz. In the 550-1000MHz bandwidth, it goes up to 8dB. Since the
higher frequencies have more loss through both the cable and the
passives (splitters), calculate using the loss at the high end of the
spectrum, which is 5-750MHz.

10dBmV going into a 4-way splitter has (10-8=) 2dBmV at each port to go
out to each outlet. RG 6 loses ~5.8dB per 100' (@750MHz), so an outlet
that's 50' from the splitter loses ~2.9dB in the cable. You had only
2dBmV to begin with and the cable is attenuating it another 2.9dB, which
means that you're going to have a signal level of -0.9dBmV at the
outlet. Throw in another 4 for a 2-way splitter, and you're down to
-4.9dBmV. Time Warner may run their systems with 20dBmV at the tap,
which would, so go ahead and add 5 to the above numbers if you want.
But that still leaves you with only +0.1dBmV at a 2-way splitter.

A pretty good rule of thumb is that if there are more than 3 outlets,
use a 15dB gain amplifier.

Always terminate unused outlets and ports on a splitter. There's
ingress and reflections to worry about.


CIAO!

Rich Gosselin wrote:

My two questions:

1. Should I get a 4-way coax splitter with each output at 7dB and
terminate the unused output? This would leave an output free for future
expansion in Room 4. I saw such a splitter at Radio Shack. Is there a
better brand?

*********************
Yes & no...if the splitter is a 1 gig splitter, it'll work. Don't use the
900mhz splitters...they'll work...so so...but you'll get better signal
through the 1 gig splitter, and they are not expensive...I get them at Home
Despots...about $5...can't remember if they are Ideal or RCA branded...you
will probably not need any signal amps...unless your really working with a
bad cable company. They take special care to boost their signal throughout
their network, and really try hard (in my area with Comcast) to pump good
signal to their users.
*********************

2. Should I terminate the cable in the unused Room 1?

*********************
Always terminate unused coax ends tied to the distribution network.
*********************


Rich