Job: 123 Fake Street, Anywhere

This is a very common thing I see. Maybe its the full moon. Who knows. But from time to time there is a rash of “my modem no longer works or has a hard time connecting”. This could very likely be due to a simple fact. When it gets really hot really suddenly coupled with electrical storms electronics can get, shall we say, hinky.

At least that’s the technical term for it AFAIK. Now, it must be human nature that whenever electronics that you don’t understand in the first place start acting up you just have to poke at them. The favorite method seems to be to randomly change things and then feign ignorance.

Tech: “Did you do anything recently?”

Cust: “No, it was always like that.”

Tech: “Are you sure, we usually don’t attach the television to the microwave.”

Cust: “Nope, been like that for years. It used to work great!”

OK, I’m not here to throw stones, I’m going to try and help you avoid simple problems with your cable modem that I see over and over (and over) again.

Now, it wasn’t all that long ago that you could do anything you wanted to the cable once it got to your house. You might degrade your pictures but if I had a hundred dollar bill every time I saw a customer with more than five televisions I could open my own check cashing joint. That’s really not the problem by itself. The real problem comes into play due to flat losses from splitting the line over and over.

Here is a simple check list for you. Find where your cable comes to your home. You should have enough signal there to do what you need to. This is the point that any technician will start with. If there is a problem here, it is out of your hands. You might need a new or better quality drop. It could be that there is a problem with the cable system itself. Experience has shown me, however, that this is not usually the problem. Sometimes it is, but most times I will find everything is OK at this point.
Now to the part that you, as a customer, probably can control. The wiring inside the house. The line coming from the system is going to have to be split if you want both television service and internet service. No way around that. There are a number of different drop splitters on the market but ones in modern systems should be marked 5-1000 MHz. Shown in the image are a handful of examples of various 2way splitters. These are the most common ones you will see. There are also 3way versions that can be used for your modem split but they must have a 3.5dB loss leg not three -7dB legs. When you get to the four (or more) range you would be better off not heading to your modem with these.

So starting at the start. The port marked IN is where the drop from the cable system goes. You might be surprised how many times I see this done incorrectly. The output ports are the ones marked 3.5dB in this case. Sometimes they will have a negative sign (-) in front of the number. That is the amount of loss for any signal traveling through that port. It will directly affect how hard your cable modem has to work to get back upstream. This will be reflected in the power that the modem needs to drive with. And that, is what we are talking about.

Basically speaking, your modem is a receiver of information from your ISP (the downstream part) and a sender back to the cable service (the upstream portion). When we talk about upstream, we are referring to the modem as a return path amplifier. That is, your modem will use as much power as needed to get to the first return amplifier so that it can find it’s way to the internet. This capability will vary from modem to modem but it is safe to say that there is not an unlimited amount of power available to it. If the modem has low input levels it will have a hard time becoming part of the system. If it has to drive with high power levels back you will see terrible actual speeds or the inability to communicate at all.

So start with your visual check. Make sure your modem is connected to the first 3.5 port after coming from the system. Give yourself the best chance possible to get some respectable speeds out of your modem. But how do you know if you are actually getting there. Well, I have a meter to get all that information. I bet most people reading don’t. I’m positive that very few of you will plunk down the money for one of these.

But there is hope. You can find out some information right from your PC. Really. It just might take a little bit of research for you to do. What you will need to do is find out the administrative IP for your modem. To help with this visit your manufacturers website. My LinkSys has an administrative interface that can be viewed in my browser at http://192.168.100.1 but yours may or may not be the same. That may work for you. I’ve used the same one for a Motorola as well. That will give you some basic information about your modem. Mine shows me my MAC address, serial number, etc etc. I also have a tab marked connect. That is where the really good stuff is.

For example, this morning I am looking at levels of,

• Downstream Power -1.1 dBmV
• SNR 31.9 dB
• Upstream Power 41.3 dBmV

The SNR is signal to noise ratio. Having this information in hand when you contact your cable companies customer service can be very helpful indeed!

Hopefully this can help you to help yourself without having to wait for someone from your cable company.