This is a little bit of a follow up and follow through to my Cable Modem entry. As I mentioned, cable RF drop splitters are a necessary evil that need to be taken into consideration in your house. There is another thing that should be discussed. RF Signal Amplifiers.

What are they and what do they do?

A RF Signal Amplifier or house amp, is a device used to raise the signal level. They come in all flavors from many different manufacturers and amounts that they amplify. Very often, if you have a large number of television sets you will be using one of these devices. If you ever had Dish Service you may also have one of these in your attached garage or basement. While they are very useful when used properly, they often are the cause of trouble with your television or cable modem.

Don’t get the impression that I want you to start yanking all house amps out. On the contrary I find them to be useful when they are useful. Unfortunately, like most electronics, they need to be considered carefully for the health of your house wiring. Your cable company will most likely only provide you with enough signal to be split into unequal thirds. That is to say, you send a low loss leg to your modem and have two high loss legs to your television sets. This is sufficient for most applications. However, most applications is not the same as all applications.

As everyone has learned from my splitter article, only split things as much as absolutely needed. Having twelve lines running to locations all over your premises may seem cool but it has its downside. Unused lines can be a place that ingress can get a foothold. Simply put, ingress is any over the air RF that finds its way in to your wiring. I won’t even try to list all of its causes. All you need to know is that there are so many things that can “broadcast” RF that you need to protect yourself from it. There is also the degrading of the signal from splitting over and over.

Enter the house RF Amplifier.

Cable TV is simple. A signal is provided. It is reduced by distances of cable and equipment in line. When it reaches a certain level, it is amplified and the process is repeated. The exact same thing happens in your house. The problem is that there are lower limits that have to be respected. The more you take away the worse the noise will be when it amplified, or raised, again.

And once again, the “trick” is simple. Only amplify as much as needed. Don’t wait until the signal has degraded so far that you are just amplifying junk. There is no way at all that garbage signal quality will be miraculously fixed by making it stronger. All you end up with is a higher level of absolute junk.

On to the solution.

The best way to deal with this is to think things through first. Don’t just flail away wildly and expect to get good results. Your little home cable system will serve you so much better if you plan first, act second. As with anything, break it down into its components and find your needs. Here is a little checklist to help.

  • Do you have or plan to have a cable modem?
  • How many televisions do you want to use?
  • How far away are each of the locations?

Pretty simple. Of course it is, it’s a simple example after all. I will assume to start that you will have a modem and that you want to have three televisions. The modem will be in the office and the televisions will be in the living room, bedroom, and kitchen. The office is centrally located, the living room is right above the cable entry point, the kitchen is on the other side of the house on the first floor and the master bedroom is upstairs on the other side of the house. We will assume that all the cable is in place.

As I mentioned before, will mention now and without a doubt will mention again, the modem needs to come off of the first splitter and be on a low loss (-3.5 dB) leg. Don’t tell me how yours works in some other configuration. Two reasons, I don’t care and I know it may work. I want you to try to get the best service, not substandard service. We still need three more legs for video service. When you estimate the lengths you come up with your bedroom being the longest, the kitchen being a little bit shorter and your living room being the closest. In fact, the living room is so close that it may actually be worse if we amplify it. So we choose an unbalanced 3way or two 2ways. Do the math. I’ll wait. Each two way has a 3.5 dB loss on each leg. An unbalance three way has a 3.5dB and two 7dB legs. So If you use a 3.5dB leg to feed a second 2way you end up with, ta-da, 7dB of loss on two available ports. Same as the 3way. Neat-o.

Wait a minute, I want 3 televisions, not two. If you came up with that on your own, bravo! You are paying attention. If not, go get a calculator. Just kidding, have your kid do the math for you. :)

We have decided that 7dB of loss is acceptable for the short run to the living room. Hook that line up to one leg. TV is working at one set. Groovy. Now, if we are using a 3way we have one more port left. Try this. Put a 2way splitter on that and attach the kitchen and bedroom lines. I’m going to assume that the 10.5dB of loss makes those sets a bit fuzzy. That’s no good. So we get a 10dB RF amplifier from wherever. Maybe your cable company provides it. Maybe you went to your electronics store. Just so long as it is for video it should be clean enough for your purposes. Don’t scrimp. Get a good one.  From the last 7dB down leg go to the input of the amplifier. On the output put a 2way splitter and connect the remaining lines.

Enjoy your clean and clear pictures and fast modem. You deserve it for managing to pay attention to my ranting.