Split Cable Modem Line For TV Tuner?

[Some Guy]

Hi,

I'd like to know what problems to expect if i try to split my cable internet
line right before the modem to accomodate a new TV tuner card.

My line looks like this:

CATV Jack - Cable Company Installed Splitter:
Splitter output 1 goes to my TV in the living room (which I will split to
reconnect the upstarirs TV in the master bedroom.
Splitter Output 2 goes on a long journey to my room to my modem. I'd like to
split this line just before the modem and have:
Splitter 2 - Output 1 to Modem, Output 2 to Tuner.

What can I do to keep signal strength up?

I also plan to install a switch to run my internet to a second computer.

Thanks,
Jesse

 

[Stephen B]

Hi,

I'd like to know what problems to expect if i try to split my cable internet
line right before the modem to accomodate a new TV tuner card.

If your current signal levels are good enough you shouldn't have a problem as
long as you are using a high quality splitter. If the modem loses sync or fails
to get sync after you make the split, you may need to go back to the first split
and split the TV side into 3 to feed your TV tuner card, Living Room and
Bedroom. Of course, the latter means a new long run on RG6 to the tuner card
from the original split, but it's your best option. If you don't want to do this
and the new split at the modem causes problems, you can get a high quality cable
TV amplifier that allows two way amplification. These are not the kind you pick
up in Radio Shack or Home Depot. I got one from these guys:
http://www.cabletvamps.com/Info/TV_AMP_EDUCATION.htm
In my setup, I chose not to amplify the signal to the cable modem, but the TV
side of the first split had to be split quite a few times more. It made a big
difference in picture quality.
Good luck,
-steve

 

[*Vanguard*]

Hi,

I'd like to know what problems to expect if i try to split my cable
internet line right before the modem to accomodate a new TV tuner
card.

My line looks like this:

CATV Jack - Cable Company Installed Splitter:
Splitter output 1 goes to my TV in the living room (which I will
split to reconnect the upstarirs TV in the master bedroom.
Splitter Output 2 goes on a long journey to my room to my modem. I'd
like to split this line just before the modem and have:
Splitter 2 - Output 1 to Modem, Output 2 to Tuner.

What can I do to keep signal strength up?

I also plan to install a switch to run my internet to a second
computer.

Thanks,
Jesse

The 2-way splitter installed by my cable company (since I have both
cable TV and broadband Internet services) has the following markings:

5-1000 Mhz
120 db EMI isolation
3.5 dB (on each "out" tap)

Don't get more splits than you need. That is, don't get a 4-way
splitter when you only need 2 splits and think that putting a 50-ohm
screw-on terminator on the other unused taps is okay. Just get a
splitter that does minimally what you need. Pretty much this looks to
be equivalent to the type of 2-way splitter you can get at Radio Shack
(http://snurl.com/rs2waysplit).

I have a Motorola Surfboard external cable modem. I can see its admin
page by browsing to http://192.168.100.1/. By going to the Signal page
I can see what are the downstream (PC side) and upstream (provider side)
signal strengths. Currently I have 5 dBmV on the downstream side and 45
dBmV on the upstream side. You will be installing the splitter on the
upstream side. If you can get a similar page (or utility to show this
info) then check the upstream signal strength at the cable modem before
and after installing the 2-way splitter. This will let you know how
much the signal got attentuated to the cable modem. If you use an
amplifier, you can also check the upstream signal strength at the cable
modem. To low a signal and you'll have problems but also too strong a
signal can cause problems (at one time my cable company actually had to
insert an attenuator to bring down the signal strength to eliminate
problems; the symptom was too many lost packets but the cause was too
strong a signal).

According to the article mentioned by Stephen, the 3.5 dB attenutated
output taps will reduce signal strength by 56%. If your cable modem has
a web page or utility to show its diagnostics and to show signal
strength then you can verify if it this actually happens in your
scenario.

 

[DaveW]

If your cable company has decent signal strength, which most do, you should
easily be able to split the signal at your computer based on how little else
is hooked up in your house.

 

[Todd H.]

Hi,

I'd like to know what problems to expect if i try to split my cable internet
line right before the modem to accomodate a new TV tuner card.

My line looks like this:

CATV Jack - Cable Company Installed Splitter:
Splitter output 1 goes to my TV in the living room (which I will split to
reconnect the upstarirs TV in the master bedroom.
Splitter Output 2 goes on a long journey to my room to my modem. I'd like to
split this line just before the modem and have:
Splitter 2 - Output 1 to Modem, Output 2 to Tuner.

What can I do to keep signal strength up?

A high quality splitter, high quality cables, and proper termination
of all signal lines (e.g. don't leave one unconnected after the
splitter).

Aside from that, there's really no way for anyone here to tell you
what to expect aside from that, as it depends on the strength of the
signal at your particular house. Odds are, it won't cause a
problem..and if it does, it's trivial for you to undo the change and
divine another way to drag cable to your TV tuner card.

Best Regards,

 

[CBFalconer]

I'd like to know what problems to expect if i try to split my
cable internet line right before the modem to accomodate a new
TV tuner card.

A properly matched passive splitter has a 50% loss from any port
to any other port. For cable internet you have to feed both ways,
so you need passive splitters. All 3 ports on a properly designed
passive splitter are equivalent, and all three should feed
properly terminated lines.