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Coax splitter problems
July 9, 2006 9:35 AM   Subscribe

What can cause a coax splitter to go bad? I've narrowed our connection problems down to this cause, but can't figure out what's causing the cause...

Cable and Internet work fine as soon as you replace the splitter. Within a day or so, though, the problem is back. I know it's the splitter because a) I've gone through three of them now, and b) everything works fine FOR GOOD if you just join the coax from the street to an individual line using a female to female splitter. Problems only arise again when you try to split the signal for use with more than one device (say a TV and a cable modem). Any ideas?
posted by richmondparker to Technology (11 answers total)
 
I have nothing but trouble with coax splitters, particularly if you've got a noisy device (a duff TV) on one end. It's probably the TV's fault, not the splitters.
posted by bonaldi at 10:02 AM on July 9, 2006


Before I say anything let me say I don't have an answer.

Wow, I thought I was alone! I had the same problem, My internet connection would drop after about 10 minutes, I would unplug the splitter, then reconnect it, that would get my internet back but it would fail again after a while.
I went thru three splitters before the problem went away. I even bought a new cable modem, it made no difference. In my case, I had TV, but no internet. I cleaned off the center copper wire on my cables and that seemed to make more difference than anything, I did that when I replaced the splitter with one from Radio Shack, so I don't know if it was Radio Shack's splitter that fixed it or me cleaning the center copper wire in the coax. The only thing I could think of was water, be it from rain or simply high humidity. I also remember Tech Support at Cox Cable asking me to tune my TV to the lowest channels and observe the quality of the picture cause that's a good indication of your signal strength. Just wanted to let you know I had the same problem and it went away after cleaning the central coax copper wire and replacing the splitter.
posted by BillsR100 at 10:02 AM on July 9, 2006


I was having all sorts of signal issues (screeching noise/picture loss/etc) with the tv that was sharing my split cox cable internet connection. The cable guy replaced the cables, the cable box, the splitter and then boosted the signal outside at the box. He did the signal strength test before and after and it really helped. In addition, my cable internet speed went from 3mpbs to 12!

Call the cable company and ask them to send someone out - they should be able to fix it.

Always tip your cable guy.
posted by sciatica at 10:22 AM on July 9, 2006


By nature, a passive coax "splitter" will introduce a minimum of 3 to 12 db of signal "insertion loss," per leg, in a line, depending on the number of legs and the design of the splitter. Moreover, the loss may not be linear with frequency, and with more and more cable systems going to broadband, the availability of splitters with greater bandpass characteristics has confused the marketplace. Generally, you want to use a splitter with the minimum number of output ports, as the more ports, the more loss you are introducing.

The cable company tries to deliver a level of signal that will stably operate the outlets and devices you have connected, without loading their lines unduly, which can affect other downstream subscribers. Too much signal, or imbalanced high and low band signals are just as frustrating as too little signal, and even long coax cable runs can result in enough variable loss to significantly complicate matters. So the cable company compensates for these variables by changing the gain of inline amplifiers out on the service drop, or by "padding" the signal with fixed attenuators to achieve a desirable signal level.

Premises wiring problems can also be at the root of intermittent operation, particularly if your home is wired with older RG59 coax, and your are having either grounding or signal ingress problems (these conditions would generally need to be checked by a technician with appropriate test equipment, although if you suspect signal ingress, and are familiar with "wiggling" coax connections, you might find the problem by physical manipulation). It sounds like you are either inserting a splitter of incorrect bandpass characteristic for your cable system, or you're on the lower edge of the acceptable signal level for operation of your modem. If your using an incorrect splitter like the old 900Mhz types, the fix may be to buy a better splitter, but that's not usually the case. On most cable systems the signal level will vary 3 to 5 db in normal operation, due to weather conditions and temperature changes out "on the pole" (i.e. through the distribution system media). When you drop below the minimum level for your modem/cable boxes, things get noticeably bad. There's not much you can do inside the home to correct this, as even installing an active amplifier won't improve the signal to noise ratio you get on a low line level signal. You need to contact the cable company, and have them check your signal, with your splitters inserted, and have any necessary level corrections made out on the pole.

DSLReports has a decent do it yourself FAQ for cable wiring issues, with pictures and lay language comments that may help.
posted by paulsc at 10:23 AM on July 9, 2006


It could also be the connectors on the end of the cables, not the splitter. If they are of low quality (*cough* twist-ons *cough*) or not installed properly, it may be that even the momentary flexture at the end of the cable when you pick it up to replace the splitter is enough to get a signal, but as it relaxes after you put it back down the physical connection loosens.

I would definitely recommend getting a quality pair of crimpers, then lopping off all the connectors involved and crimping on new good ones. This is likely one of the first things the cable company's tech should do if you decide to go that route. If you do this yourself, be prepared for the first few that you do to be crap, as there's definitely a bit of skill involved.
posted by Rhomboid at 11:15 AM on July 9, 2006


Coax splitters are wound on toroidal cores made of powdered ferrite and other magnetic materials. If the toroidal core cracks from age, cold, temperature swings, freezing with trapped water, mechanical shock/vibration, mechanical overstress from screwing-down the case too hard, etc., I believe the splitter will stop working.
posted by ZenMasterThis at 12:57 PM on July 9, 2006


Just to clarify...

My problem is primarily with the cable modem dropping the connection...while the low channels on my TV lose a little quality, they are still acceptable.

I have called the cable company numerous times. Different technicians tried different things, and ALL worked for a few hours before the connection finally went away for good:

1. All connectors were replaced (I had the "old" kind which were "famous for this sort of thing")
2. Cable modem was replaced (they had originally installed a modem/telephone and one technician suggested that the connection was being reset each night when the company did their check for line activity since our phone is not through Comcast.)
3. Connection and signal strength were checked at the pole. Signal strength was "excellent" both there and inside where it connects to the modem).
4. Splitter has been replaced 3 times.

So far the only permanent fix has been to run only one device at a time using the female/female connector described in my original post.
posted by richmondparker at 2:06 PM on July 9, 2006 [1 favorite]


Are you certain the problem lies on the RG-6 (coax cable) site and not on the network side? Are you using a router of any kind?
posted by Merdryn at 3:15 PM on July 9, 2006


Yes, I am using a Linksys router, but do not suspect that it has anything to do with the problem. My connection is perfect with the female/female connector whether I'm going through the router or not. Likewise, the problem persists even if I run the cat 5 directly to the computer from the cable modem when I'm using a splitter.
posted by richmondparker at 3:56 PM on July 9, 2006


Ah, Comcast.

Much of their service work is outsourced to local technicians, who are generally capable guys, but who work with limited information regarding the actual distribution system. I've had 3 cable modems in 1 year and 3 months, and that's a pretty standard "fix" for Comcast distribution problems, if you read any of the ISP rating sites. Obviously, problems aren't always reliably cured by hardware fixes, but in fairness, you do have to work through the issues step by step to demonstrate that the root of your problem isn't hardware or cabling issues.

If your premises wiring has been as thoroughly checked for levels and signal ingress as you seem to think it has, you need to try to get your problem escalated. This is only going to happen if you start calling repeatedly, and the phone support techs can see level problems or bit error rates being reported back by your cable modem (which they can, in real time, by looking into the modem's internal Web server, and reading the error log. You can too, before your modem gets its DHCP address from the network as it's temporary internal address will be 192.168.100.1 until it completes its network check and address negotiation). Over time, your trouble reports build a pattern that may get you re-provisioned.

But it can take a while; be persistent.
posted by paulsc at 5:59 PM on July 9, 2006 [1 favorite]


Also, have you checked to be sure your Linksys router is flashed to the latest firmware? Check your router's sticker for model and hardware version number, and plug in to linked page to see. Compare to version numbers on admin sign in page in your router's internal administrative Web server, if you have fairly recent firmware. How to flash your router FAQs.

Older Linksys routers (and other brands, too) had problems with PPPoE protocol negotiation that would cause frequent drop outs in use, resulting in frequent or long re-negotiations; looked like flaky or dead connections to the user, and created lots of spurious traffic on cable systems.
posted by paulsc at 6:13 PM on July 9, 2006


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