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My first suggestion of all is going to be:DETERMINE WHETHER THE PROBLEM IS INSIDE OR OUTSIDE BEFORE DOING ANYTHING ELSE
The easiest way to do this is by taking the cable modem out to the ground block (where the cable attaches to your house) and plugging the modem DIRECTLY into the drop (the line coming from the cable company). If you still have problems, you either have a bad drop (or bad ground block) or something is wrong in the plant (the cable company's system).
Yes, you will need to borrow a laptop, or run a long network cable to your computer to test the modem. Do NOT run a long cable wire from the ground block to the modem, unless it's 100% brand new.
Feedback received on this FAQ entry:
- Cable modems are a lot more sensitive to signal quality than the television receivers. They need to fall within a certain signal level parameters. If you are experiencing intermittent internet you need to check the signal levels and splitter configurations to diagnose the issue. The modem should have an interface that you can access from an IP address. If you don't know what your modems IP address is, try googling the model number of your cable modem + IP address. you may also need the default password.
Once you are in the interface you need to check for four things. Downstream, Downstream Signal to Noise Ratio (SNR) Upstream, and Upstream Signal to Noise Ratio (SNR).
Downstream: -8dBmV to +5dBmV (This is my personal preference. Other sites say -15dBmV to +15dBmV is the max, but you will rarely see it working consistently above -10dBmV.)
Downstream SNR: 35dB and higher (the higher the number, the better)
Upstream SNR: 35dB and higher (the higher the number, the better)
Once you check the signal levels you can start to diagnose the issue.
1a. Downstream Signal level is too Low (this is about (90% offender) - If the downstream is above -8dB, then you know you are getting a bad signal coming into the house. Check the splitter configuration. You will need to check it at two locations - one at the modem to see whether it is being split to also a TV and also at the TAP outside (The location outside your house where the cable providers cable comes to your home. The splitter may be in a box. Sometimes people may put splitters underneath the house as well. Just follow the lines from the pole outside to your home).
A bad signal can be because of a wrong type of splitter (make sure the splitter is 1000 mhz or higher), bad splitter configuration (using a four way splitter when you could use a two way splitter), or a bad coax cable in the house (RG-59 is a major offender, so is copper braided RG-6 and Copper Clad RG-6 cable).
Remember every time you use a splitter it cuts the signal level in half (eg. a four way splitter cuts the signal four times. A two way splitter only splits is twice).
You can always use a two way splitter from the tap. One leg goes directly to the cable modem and the other leg goes to another splitter that feeds all the TV's in the house.
If the splitter configuration is at its most optimal configuration and it is still not working, check the cabling that is going to the modem. Is it an RG-59 cable (big offender)? You may need to replace the line to RG-6.
If you still cannot get the downstream within parameters, call your cable provider because their equipment on their end is faulty.
1b. Downstream is too high (8% offender) - If the downstream is coming in really high (+5dBmV or higher, put a bigger splitter in front of your modem (that will cut the signal strength and it will fall within parameters.
2. Upstream (1.5% offender) - Most of the time you will find nothing wrong here. If the upstream signal level is really high (above 52 dBmV) AFTER you have worked on the downstream and got the downstream within parameters, call your cable provider. They have a TRAP outside your house (they use to use these a long time ago when they were sending Analog signals to your TV. They were used to block people from stealing their TV service. They also use it today if you have bad cabling and are causing a lot of noise on the line and it is affecting the neighbors signals around you). A tech will go outisde your house, climb a pole and remove the trap.
3. SNR (0.5% offender) - This is the last step to check. If your signal to noise ratio on either downstream or upstream is really low, then you need to check for bad splitters, bad fittings, bad barrels, coaxial cable that is ran alongside a power cable or power line (if you have to run the cable with the power line, then use quad shield cable AND/OR make sure it is ran 12 inches away from it), and bad cabling where the insulation is exposed (eg. a rodent chewing on the cable and it has chewed through the shielding). It maybe one or a combination of these problems that is causing you to have a bad SNR. Crimped on connectors can leak noise into the cable. Redo the ends with compression fittings. If you find that a rodent chewed on the cable, then you will need to replace it.
This is my guide. If you follow these steps, your internet will be up and running in no time. The only thing I did not mention was amplifiers because that is another topic.