CATV

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Cleveland Apprentice

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Cleveland, Oh
I don't have too much knowledge with CATV other than knowing how to put connectors on.

Does anyone know or have any links regarding maximum distance permitted for CATV runs and how many times it can be splitted? I plan on running new RG-6 Quad shielded CATV lines to a 2nd floor of a house. There are a total of 5 cable jacks with 1 being for internet. I plan on running 2 CATV lines to 2nd floor. 1 dedicated for the internet and the other going to a splitter with 4 outlet ports which goes to the other 4 CATV jacks. I would home run all back to the main splitter box on outside, but only have 1 3/4" pvc chase from basement to 2nd floor limiting me to 2 or 3 CATV lines max. All runs are 120' or less. I am not sure how much DB I would lose with the splitter and wondering if this installation would be ok? Any feedback and reference links would be appreciated!
 
Cleveland Apprentice said:
I don't have too much knowledge with CATV other than knowing how to put connectors on.

Does anyone know or have any links regarding maximum distance permitted for CATV runs and how many times it can be splitted? I plan on running new RG-6 Quad shielded CATV lines to a 2nd floor of a house. There are a total of 5 cable jacks with 1 being for internet. I plan on running 2 CATV lines to 2nd floor. 1 dedicated for the internet and the other going to a splitter with 4 outlet ports which goes to the other 4 CATV jacks. I would home run all back to the main splitter box on outside, but only have 1 3/4" pvc chase from basement to 2nd floor limiting me to 2 or 3 CATV lines max. All runs are 120' or less. I am not sure how much DB I would lose with the splitter and wondering if this installation would be ok? Any feedback and reference links would be appreciated!
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The splitters should be marked with the dB loss and add any in series together.

How do you plan on going from line to 5?

Basically, each tap would have 1/5 the signal as the incoming line, if balanced. But, chances are you would have two 10.5 dB ports and three 7 dB ports.

You may be OK, you may need an apartment amp or you may need to call the CATV company to make sure you have enough signal.

Since you don't know how strong the signal coming in is, the dB loss values aren't going to be much help. I have seen houses with a half dozen splitters and good signal to 6 outlets, and have seen as little as 3 degrade the signal terribly because the incoming signal wasn't strong enough to begin with.

IOW, one place had 15 - 20 dB splitter loss and still a good signal at the end, the other had two 7s and a 3.5 and had a bad signal at the end, even at the 3.5dB tap.

Every time you split, you lose 3.5 dB. So going from one to two you drop 3.5. From 2 - 4, you are 7 down from the incoming. Each time you add a split, you drop 3.5.

(Three way splitters are basically a 'V' with one leg split again. That's why the two 7's and only one 3.5)
 
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You'll need a standard 15dB gain drop amp to feed 4 outlets at that distance. Split the incoming line for the cable modem outlet prior to the drop amp. Run a cable to a central location where you'll locate the 4-way splitter that will feed the TV outlets.
 
I would suggest that you run the coax and let the cable company deal with the splitters and amp if necessary. They don't charge that much and have the proper equipment to make sure the signals are correct.
 
If its at all possible run (tagged so you know where it goes) each as a home run to the cable company's demarc that way you can minimize the loss and have the cable company do the splicing with thier splitters.
 
BTW, you can get a "balanced" 3-way splitter that is about 5.5 dB loss on all three outputs instead of 1 x 3.5 db + 2 x 7 dB. You'll pay slightly more; the single-point split is a better quality method but costs more. 4-way and 8-way splitters that have single-point splitting will typically have losses of 6.5 dB and 10 dB instead of 7 dB and 11 dB when they build them by stacking 2-ways. It's normally not worth worrying about, but it can be worthwhile when you have a weak input signal and an extra 1 to 1.5 dB from quality splitters saves you from adding an amplifier. If you do need an amplifier, you'll need to make sure it has a reverse path if the customer is going to use cable for Internet or phone. That, in itself, is a good reason to avoid the amp if at all possible.
 
Some off the shelf amps are noisy.

There was one in my neighborhood that was interfering with the amateur radio part of the spectrum. I helped the CATV guy locate it using radio direction finding equipment after they spent several days trying to find it (the source of the interference). They wasted a bunch of money in the process swapping out pole mounted devices with their trial and error approach.

I found it in five minutes. CATV guy caught up with customer the next day or so and had her swap out the noisy amp. This amp was about 300 feet from my home and made a small part of the 2 meter amateur band unusable.

At the time, I had two CATV amps that made no RF interference at all.

BTW, if you have a device that interferes with other parts of the radio spectrum, especially the licensed spectrums, you can get into big trouble with the FCC. The fines are 8 to 20 grand or so if you don't correct an FCC complaint.
 
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