Why does this cable splitter screw up my modem? What can I do about it?

February 26, 2013 10:04 AM

Wall<>Cable Modem = Good. Wall<>Splitter<>Cable Modem + TV = Intermittent failures where the modem goes off line. What can I do to improve this? Is there such thing as a lower power splitter? Better cables? And did my cable company make a mistake? More details below!

Recently I changed apartments.

In my old apartment, the cable guy came and set up my cable modem in this way: Wall<>Splitter<>Cable Modem. There was nothing at the other end of the splitter as I didn't own a TV. It was strange I didn't question him. Things worked well.

I moved and got a TV hand me down. I didn't order TV services though. On a whim, I set it up such that it is Wall<>Splitter<>Cable Modem + TV and was pleased to discover that I get the local channels! Hurray!

But now, every few days, my cable modem gives up the ghost and can't connect to the cable network. To solve this, I have to connect my modem to the wall directly, wait, and then try the splitter again.

1. Is this, uh, considered, getting cable service for free? Even though all I get are the over-the-air channels?

2. Is there anyway I can connect my TV and Modem to the network effectively?

Thanks.

posted by bluelava to technology (14 answers total)

It sounds like your splitter may be faulty - if the channels you are getting are simply the local ones and not basic cable, those are readily available anywhere and there's no reason you wouldn't be able to draw a cable signal and an internet signal through that splitter. That's what it's designed for.

You can buy a splitter at a local tech store for very little money and swapping them out is quite easy. I'd start there before contacting the cable company.
posted by Rodrigo Lamaitre at 10:11 AM on February 26

More details: my splitter says it is 5-1002 MHz, and all of the output plugs are marked as -7db.

What should I look for in a splitter?
posted by bluelava at 10:19 AM on February 26

If it is for regular digital cable, you don't need anything higher than 1 Ghz. Don't spend more than a couple of dollars on this.
posted by griphus at 10:45 AM on February 26

All splitters attenuate the signal coming through as part of their normal functionality. It is quite possible that the signal coming out of your wall jack is not strong enough to be split and still support the cable modem. It's worth replacing the splitter, and also replacing the pieces of cable in between (also try to use the shortest ones possible -- don't use a 25' cable to go 2'). Make sure you just get a 1->2 splitter; the more outputs it has, the more it attenuates, so if you replaced it with a 1->3 or something, you'd just be exacerbating the problem. If replacing the splitter doesn't work, you're probably going to need to get the cable company involved to figure out why your signal isn't strong enough. But if you're not actually paying for the TV service, this might be problematic (in their eyes, there's no reason you need to be using a splitter at all -- for Internet only, you'd be better off connecting the modem directly to the wall).
posted by primethyme at 10:56 AM on February 26 [1 favorite]

Um, yes, you are stealing cable TV service. If all you want is local channels, get a small antenna for the TV and run the cable directly into the modem.
posted by Marky at 11:12 AM on February 26 [1 favorite]

radio shack sells a signal booster/splitter, if it comes to that point; it has to be plugged in, but I used it in an old house with beat up cables and it made a big difference.
posted by lemniskate at 11:13 AM on February 26

You need to replace the splitter for sure - a -7db drop is typical in a coax splitter with 3 or more legs, but a simple 2-way splitter should only have a -3.5db drop. If your splitter *is* a 3 or more way, one of the legs *should* be marked with only a -3.5db drop - you can try hooking the cable modem up to that leg. (These things do vary, hence *should*).

That being said, if eliminating the splitter altogether eliminates the problem? Then some combination of low signal / high noise is your issue (possibly owing to other upstream splitters between you and the tap out on the pole / in the lockbox / in the ped / wherever.

As this is an old apartment, your drop (the piece of coax that connects you to the tap) could be the issue. Is it RG59 coax? (it should be RG60, or might even be RG11 for the drop itself and RG60 internally).

And yes, you're stealing basic cable by hooking up a TV. This is possible because in most instances, the first 23-or-so channels (typically referred to as "basic cable") are broadcast unencrypted, and thus your tv is perfectly able to decode and display them. Your installer should have put a trap (an in-line filter) on the line to block those unencrypted channels. That he did not (either by choice or omission does not justify the theft, but it explains why it is possible.

I'm skeptical that a radio shack style signal amplifier would solve the issue - there's almost certainly enough noise on the line that amplifying it would just make the problem worse (at least, that's my gut feeling, without being able to hook up my wavetek and see the levels myself.)


/spent multiple years as a CATV splicer.
posted by namewithoutwords at 11:37 AM on February 26

Getting local channels over the cable line is not "stealing cable" - it should be the exact same content as Over-the-Air. The in-line filter installed at the cable box does not necessarily block "Over the Air" channels - it seems like cable companies have the right to encrypt those channels along with basic cable, but otherwise they are no different than OTA channels.

If the in-line filter wasn't installed, bluelava would likely also receive basic cable channels. That doesn't sound like the case here.
posted by muddgirl at 11:49 AM on February 26

I had a similar problem at one point, and in my case I solved it by getting a new splitter. I was told at the time that, basically, splitters degrade after a while, and that it would need to be replaced every few years or so for the same reason.
posted by kyrademon at 1:14 PM on February 26

Whenever I've had both cable TV & cable modem service in the past, both in an apartment & house, it was split by the cable company before it even entered the building. They took care of that.

I'd first do what others are suggesting - get another splitter, cheap & worth a try. Home Depot, Radio Shack, probably Wal-Mart. Even Walgreens or a supermarket often has these.

If you'd like the cable company to take care of this for you just sign up for TV service for a month. Ask them what you can get without a converter box, have them install the 2nd cable run, then cancel the cable TV the next month.

The very basic cable may even be included with your rent, or the cable company may not care if you're paying for cable modem service - it is just free OTA channels anyway.

Another option is to just get an OTA antenna - broadcast channels are much better now that it's all digital. More channels and really clear, though it is more all-or-nothing, you can't watch a weak channel from far away with a lot of static, it just won't work at all with a really weak signal.
posted by NoAccount at 1:19 PM on February 26

Jeez, cable companies know that people get basic cable on internet-only subscriptions, I first heard about it maybe 10 years ago. They don't care; it's not stealing.
posted by rhizome at 1:36 PM on February 26 [1 favorite]

Technically it's "passive theft of service," which I find sort of silly as a legal concept. But that's basic cable. Bluelava seems to be talking about OTA channels that are rebroadcast over cable lines, unencrypted either due to rebroadcast agreements or because cable providers don't care if you are watching local channels on your cable line.
posted by muddgirl at 1:39 PM on February 26

Your question is too generalized for the specific answers I would give.

( A splitter with an unterminated port versus a splitter with a terminated port will behave differently. It's complex. Add to that the fact that the modem signal is bi-directional and while I've dealt with designing amplifiers that work on cable/internet distribution systems, I've never considered a splitter scenario. )

So.... just unplug the cable going from the splitter to the TV and see if it makes a difference. May take a day or two, but a test is a lot better approach than guesses from out here with no instrumentation.

If the problem goes away, hook it back up and see if it returns. If you can make the problem go and come at will, you have the basis for a new question that can get resolved.
posted by FauxScot at 4:54 PM on February 26 [1 favorite]

My understanding is that the FCC only recently gave the cablecos permission to encrypt OTA content, ending what was known as "clear QAM" along with unencrypted basic cable. Most cablecos only recently sent out notice of the coming change, and access will be lost sometime this month. There was no theft of service under Clear QAM, active or passive, if you were only getting OTA channels.
posted by snuffleupagus at 3:57 PM on March 7 [1 favorite]