On Wed, 03 Nov 2004 10:04:53 GMT, Jerry wrote:
Cable comes into my house's outside junction box into a 4-way splitter
with each output saying 7dB (whatever that means), then goes to four
rooms.

Usually that "7dB" means the output has 7dB less signal strength than
the input. In this context, 3dB down means one-half (1/2) the signal,
so 7dB means 1dB less than 1/4 the signal. In an ideal 4-way splitter,
each output would have 1/4 the signal, so your splitter has some 1db
additional real-world loss (expected, and 1db is OK, 1.5db is bad).

To overcome loss and signal division, you might need to add a
distribution amplifier before the first splitter in the junction box.
Usually a cable company will install one, especially if using a cable
modem. This is usually a box with a cable in, cable out, and a cable
connected to a power adapter. Sometimes you can get an amplifier
combined with a splitter. I don't like those.

In addition to a loss specification, the bandwidth of the splitter (or
amplifier) is often specified. For satellite and digital cable, and my
preference in all installs, are splitters with a bandwidth up to at
least 1ghz.

Room 1: Bedroom without any TV. Coax not terminated.

Room 2: Office with cable modem and TV. Cable company used a 2-way
splitter with each output saying 3.5dB.

That splitter shows that each output gets a little less than 1/2 the
input signal, or less than 1/8 of the original signal (1/4 divided by
2).

Room 3: Bedroom with a TV.

Room 4: My main media room. Here's where I need the right coax splitter.
I currently have a 2-way splitter connected to a VCR and a TiVo. I'd
like to add a DVD recorder with a cable-ready tuner. All 3 devices would
have coaxial RF cable input.

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.

A 4-way splitter would cut signal strength in half to each of the
devices currently connected to the 2-way (from 1/8 to 1/16).

A 3-way splitter (or two of them) would give a slightly stronger signal
if used instead of the four-ways. Splitters are also available in 6-way
and on up. Just a bit harder to find. I've had good results with
the high-grade (low loss, wide bandwidth) splitters from MCM
Electronics.

Can you run any additional coax from the junction box to the various
rooms? My preference would be to disconnect (at the junction box) Room
1 (since it isn't used) and run that output via a new line to Room 4.

Now with 1/2 the available signal in room 4, you can run 1/8 1/8 1/4 to
three devices, or add a 2-way splitter and run 1/8 1/8 1/8 1/8 to four.
Or you could replace the splitter in the junction box with a bigger
number of outputs and that way everything would have equal signal.

If you ever have cable modem problems with signal strength, you could
either run a second line to room 2 (one for each device) or else use a
2-way splitter at the junction box before the 4-way, connecting the
4-way to one output (1/2 the signal) and the room 2 line to the other
(1/2 the signal to room 2, where it gets split so each device gets 1/4
instead of the current 1/8).

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

In theory, all unused outputs should be terminated. It might or might
not make any noticable difference.

sdb