# One cable wall outlet for cable and modem? **URL:** \ **Category:** Factual Questions\ **Created:** [April 13, 2006, 12:29am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459 "2006-04-13T00:29:37Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![TommyTutone](https://avatars.discourse-cdn.com/v4/letter/t/c4cdca/32.png) [@TommyTutone](https://boards.straightdope.com/u/TommyTutone)\ **Post date:** [April 13, 2006, 12:29am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/1 "2006-04-13T00:29:37Z")
I sit here in my den on my high speed internet typing this. At the same time, I have a little television for background noise, but I only use the antenna on it. Can I use a splitter of some sort (and if so, what sort) to divide the connection from my den into both cable for the tv as well as the modem? Keep in mind that this particular outlet that feeds into my modem right now goes into a router for our wireless network. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [April 13, 2006, 12:33am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/2 "2006-04-13T00:33:57Z")
> [@TommyTutone](#): > > I sit here in my den on my high speed internet typing this. At the same time, I have a little television for background noise, but I only use the antenna on it. > > Can I use a splitter of some sort (and if so, what sort) to divide the connection from my den into both cable for the tv as well as the modem? Keep in mind that this particular outlet that feeds into my modem right now goes into a router for our wireless network. You can use a splitter but it is recommended that you use a splitter with one leg being low Ohm and connect that to the cable Modem. If you see deteriation in cable speed you might have to undo the splitter. SPlitter are generally cheap and use a good quality short cable between the splitter and the Cable Modem. Good Luck, Jim ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 13, 2006, 1:11am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/3 "2006-04-13T01:11:13Z")
With digital CATV and Internet, it’s generally not a good idea to be a DIYer. My system requires special filters on the cable modem side of a splitter. Note that if you mess up (which there is a good chance of), not only are you degrading _your_ digital CATV and net connection, you are also hurting your neighbors’ as well. Call your cable company, find out what type of splitter and filters you need and how to go about getting them. Do _not_ do this unless you are going to do it right. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 13, 2006, 1:17pm UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/4 "2006-04-13T13:17:57Z")
> [@ftg](#): > > Do _not_ do this unless you are going to do it right. Well, it’s not like a splitter at the local hardware store costs a lot of money. Why not get one for a few bucks and try it? I’ve got a 4-way splitter on my cable line and it works fine. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 14, 2006, 2:14am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/5 "2006-04-14T02:14:51Z")
> [@John Mace](#): > > Well, it’s not like a splitter at the local hardware store costs a lot of money. Why not get one for a few bucks and try it? I’ve got a 4-way splitter on my cable line and it works fine. I _seriously_ doubt that you really know whether it “works fine.” Have you tested it with modern signal meters on the full range of frequencies? Have you tested it _on your neighbors’ lines_? In all probability it does not “work fine.” You just don’t realize nor care about the degradation of signal you have caused yourself and others. Like I said, on my system, a special filter (not available at home stores or RS) is a _must_. Did you call the cable company and ask if your system needs one? What frequency range does a splitter on your system require? Do you need one that goes up to 900Mhz? 2Ghz? How do you know? ---
**Author:** ![groman](https://avatars.discourse-cdn.com/v4/letter/g/73ab20/32.png) [@groman](https://boards.straightdope.com/u/groman)\ **Post date:** [April 14, 2006, 2:57am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/6 "2006-04-14T02:57:10Z")
> [@ftg](#): > > I _seriously_ doubt that you really know whether it “works fine.” Have you tested it with modern signal meters on the full range of frequencies? Have you tested it _on your neighbors’ lines_? In all probability it does not “work fine.” You just don’t realize nor care about the degradation of signal you have caused yourself and others. I don’t know, my cable installer used a standard RCA Y-splitter that’s not capacitor coupled. It may depend on the system, and I can understand how a splitter that has a DC filter or a band-pass filter may degrade your neighbors connection but just a simple Y-splitter made by joining the wires together? What is the modem going to do that’s so different from the digital cable box anyhow? Digital cable and internet typically use pretty much the same technology using very close frequencies. ---
**Author:** ![Mathochist](https://avatars.discourse-cdn.com/v4/letter/m/c89c15/32.png) [@Mathochist](https://boards.straightdope.com/u/Mathochist)\ **Post date:** [April 14, 2006, 7:39am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/7 "2006-04-14T07:39:31Z")
> [@groman](#): > > Digital cable and internet typically use pretty much the same technology using very close frequencies. As backup to this, one of the standard troubleshooting questions when calling to complain about packet-dropping is “Are you noticing any noise on your low cable channels?” The bands are close enough that if there’s trouble on modem frequencies the lower cable channels will likely be affected as well. ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [April 14, 2006, 11:27am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/8 "2006-04-14T11:27:13Z")
Buy a splitter and a couple of short lengths of coaxial wire at your local hardware store and go at it. If you’re at all nervous about it, see if you can locate one of the CableCo installed splitters and see if it looks like it has any special features. My CableCo uses a standard, though high quality, splitter and no fancy capacitors or filters. If anything stops working, just unhook it and go back to the original setup, you’ll be out $10. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 14, 2006, 5:03pm UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/9 "2006-04-14T17:03:11Z")
> [@Cheesesteak](#): > > If anything stops working, just unhook it and go back to the original setup, you’ll be out $10. But how are you going to _know for sure_ that you are not messsing up _other peoples_ connections? This is something the people reading and posting here really need to understand. You are not just potentially messing up your connection, but other peoples as well. Secondly, note that it _varies from system to system_. What works for one poster may be a really bad idea for another to try. Is it really all that hard to call the cable company and ask? ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [April 14, 2006, 5:36pm UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/10 "2006-04-14T17:36:14Z")
> [@ftg](#): > > But how are you going to _know for sure_ that you are not messsing up _other peoples_ connections? This is something the people reading and posting here really need to understand. You are not just potentially messing up your connection, but other peoples as well. > > Secondly, note that it _varies from system to system_. What works for one poster may be a really bad idea for another to try. > > Is it really all that hard to call the cable company and ask? You won’t mess up other people’s connections. Nothing you do on your line will have any impact on anyone else’s. Doesn’t work that way. Adding a splitter doesn’t mean you’re pulling any more signal from the main line, it means that the signal you’re pulling is split more ways and is hence weaker. There are really only two significant issues here: 1) the splitter added needs to be high enough quality that it’s not unduly attenuating frequencies used by the modem. Some cheap splitters might be an issue here, so it’s best to purchase a good one. The ones available in retail outlets often vary wildly in quality. The simplest way to make sure you have a good one is to find an industrial electronics store - the kind of place that supplies contractors who install this sort of thing. 2) The signal strength at the modem needs to be in a certain range. A 2-way splitter typically attenuates the signal on each leg by 3.5dB. That could potentially be enough to be a problem, though whether it is depends on how picky the modem is about signal strength, and where in the acceptable range of strength the signal currently is. However, if this is an issue, I believe there are 2-way splitters out there that are designed so that one leg is attenuated much more than the other, something like 1dB on one leg and 6dB on the other. Hook the modem onto the 1dB leg of one of these, the tv to the other, and the OP should be good to go. Which is pretty much what **What Exit** said. Your “special filters” on the modem side of your splitter are probably pads - just signal attenuators. Some cable modems don’t like overly strong signals any more than they like weak ones. This is a little barrel with “3dB” (or 6 or 9 or 12) written on the side of it, right? ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [April 14, 2006, 11:27pm UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/11 "2006-04-14T23:27:06Z")
> [@ftg](#): > > Is it really all that hard to call the cable company and ask? Well, yes it is! I’ll have to go thru voice-mail hell, listening to all kinds of choices and pressing buttons, and then spend a long time, possibly hours, waiting on hold. And then I get a person who seems to be completely clueless about this. Seriously, I could drive to a hardware store & buy a splitter, come back home, install it and try it out, all in less time than I would wait to get an answer from the cable company. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 14, 2006, 11:57pm UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/12 "2006-04-14T23:57:49Z")
> [@ftg](#): > > I _seriously_ doubt that you really know whether it “works fine.” Have you tested it with modern signal meters on the full range of frequencies? Have you tested it _on your neighbors’ lines_? In all probability it does not “work fine.” You just don’t realize nor care about the degradation of signal you have caused yourself and others. > > Like I said, on my system, a special filter (not available at home stores or RS) is a _must_. Did you call the cable company and ask if your system needs one? > > What frequency range does a splitter on your system require? Do you need one that goes up to 900Mhz? 2Ghz? How do you know? All my neighbors that I know of do exactly the same thing. I’ve had the cable company out a dozen times, they’ve looked over my system and never said a thing about it. Heck, the splitters they install are cheaper than the ones I get at the hardware store. One thing they have done is install better connectors on the cables themselves. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 15, 2006, 2:05am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/13 "2006-04-15T02:05:57Z")
> [@Gorsnak](#): > > You won’t mess up other people’s connections. Nothing you do on your line will have any impact on anyone else’s. Doesn’t work that way. Adding a splitter doesn’t mean you’re pulling any more signal from the main line, it means that the signal you’re pulling is split more ways and is hence weaker. > > (snip) > > Which is pretty much what **What Exit** said. Your “special filters” on the modem side of your splitter are probably pads - just signal attenuators. Some cable modems don’t like overly strong signals any more than they like weak ones. This is a little barrel with “3dB” (or 6 or 9 or 12) written on the side of it, right? 1. Bzzzt. Wrongo. Try shorting the center conductor and the shield. Definitely going to cause a problem with your neighbors’ signal. A crappy splitter will also cause degradation. So will leaving off terminators on unused connectors. And so on. There are lots of ways that what a person does in their home to a cable line can cause problems outside the house. Degrading a signal is not a good thing when most cable companies are hard pressed to provide a barely usable signal at all. 2. Bzzzt. Wrongo. When I said “filter” I mean “filter”. It’s a band pass filter. If it was an attenuator I would have said “attenuator”. The range of frequencies that are blocked is, of course, “special” in the sense that not all systems need the same frequences blocked. Waaaay too many people think that all systems are alike. This is just plain not true. Even within the same town, there is variation due to consolidation. The digital cable boxes I have can’t be used by people living just two miles away from me even though it is (now) the same cable company. Let’s _fight_ ignorance and not add to it. ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [April 15, 2006, 3:10am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/14 "2006-04-15T03:10:35Z")
Except we’re not talking about shorting out the centre connector.\* :rolleyes: We’re talking about installing a good quality splitter and hooking one device to each leg. What would happen if the OP called in a cable installer to do this? The cable guy would pull out a 2-way splitter, hook the TV to one leg, slap a level meter on the other leg, and assuming the level was acceptable, hook the modem onto it. So there’s no reason whatsoever for the OP not to do this himself if he has the materials to do so, though he’ll be stuck using trial and error to determine whether his modem is happy with the resulting signal level. (Possibly his cable company charges extra for hooking up extra TVs and if he doesn’t inform them he’d be engaging in cable theft, but that’s not a technical issue.) Your scaremongering about deleterious effects on the neighbours is largely baseless. \*Out of curiosity, I tried this just now on one leg of a splitter with a TV on the other, and didn’t get any visible effects. Course, TVs are pretty forgiving of crappy signals, so that doesn’t show much I guess. I’d try it the other way with the modem on the other side, but I can’t be arsed to get at the back of the TV to do it. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [April 15, 2006, 4:52am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/15 "2006-04-15T04:52:22Z")
Wait, if what the OP is asking works out, wouldn’t he be stealing cable, then? Every cable company I’ve ever read about requires you to pay separately for an internet connection and a cable TV connection. If he’s paying for internet and getting internet and TV…isn’t that illegal? ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [April 15, 2006, 12:57pm UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/16 "2006-04-15T12:57:50Z")
> [@ZipperJJ](#): > > Wait, if what the OP is asking works out, wouldn’t he be stealing cable, then? > > Every cable company I’ve ever read about requires you to pay separately for an internet connection and a cable TV connection. If he’s paying for internet and getting internet and TV…isn’t that illegal? No, you don’t get Cable Internet service just by plugging in. The cable company as to activate it. Once you have Cable TV in your house, you are allowed to split it for basic cable signal. (This is at least true in NJ & NY) Jim ---
**Author:** ![JXJohns](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jxjohns/32/469_2.png) [@JXJohns](https://boards.straightdope.com/u/JXJohns)\ **Post date:** [April 15, 2006, 3:36pm UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/17 "2006-04-15T15:36:51Z")
> [@ftg](#): > > Is it really all that hard to call the cable company and ask? Obviously, your cable company is a step above the slackjaws working the help desk at mine. That too varies from system to system. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 16, 2006, 12:28am UTC](https://boards.straightdope.com/t/one-cable-wall-outlet-for-cable-and-modem/352459/18 "2006-04-16T00:28:25Z")
> [@Gorsnak](#): > > Your scaremongering about deleterious effects on the neighbours is largely baseless. Cite? It is so weird to see that suggesting that a poster: 1. Obtain the correct information. 2. Do things right. is now taboo on the SDMB. As to shorting out the center tap: 1. It was just one example (of many) that disproves another poster’s universal statement. 2. Guess what happens when an idiot tries to make his own cables and isn’t careful?