# Proper Splitting.



## duque00

Hey All,

Which of the following scenarios is correct.

1) Line from pole to the house comes into a 3 way splitter. One for a Modem, the other 2 to cable boxes for HDTV's. No other splitters all feed direct from splitter to the individual devices.

2) Line from pole to the house comes into a 2 way splitter. One for Modem, the other to another 2 way splitter which then goes to the cable boxes for HDTV's.

I said #1, my friend says #2 - which one is right and why?

Thanks in advance.


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## GrayHair

Two schools of thought here:
 1. Divide signals equally (assumes equal length runs)​ 2. Best signal to the cable modem​ A basic splitter divides the input equally between the number of outputs (plus insertion loss). Typical 2 port splitter will provide approx ½ the input signal at each output (around -3.5dB with insertion loss). A typical 3 port splitter will provide approx ⅓ the input signal at each output (-5.9dB with insertion loss). When you "stack" 2 two port splitters you will get approx ¼ of the original input signal (-7db) out of the second splitter.

So does one device need more signal? Which one? I had to replace a HDTV about a year ago and found the new receiver was appreciably less sensitive. Enough so that I had to reconfigure my MATV distribution system to reliably watch my favorite station on the new set.

Don't forget to look at upstream attenuation (modem talking to the cable network) of the splitters. If upstream is -12dB per splitter, there will be -24dB total upstream from stacked splitters (pulled -12dB out of thin air). I forget what the cable loss of RG6 is per 100' is but you should be able to find it if needed.

Which way is correct? The one that works best for you. If you dont' like your first choice, we aren't talking about mega bucks to redo it.


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## duque00

For my setup:

TV#1 - shortest run - 15'
TV#2 - 25'
Modem - Longest - 35'

My friend - I don't know his setup personally.

Also, someone told me that the Cable provider comes into play as well.
Is this true?


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## MisterCMK

It depends on if you have enough signal for the modem right away. Either one will work.


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## pete87

I have always brought all cable feeds to a device , back to the D-MARK .

I do the same with Telephone Cables too .

Everyone likes that best .

I like your #2 .



Pete


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## duque00

Both #1 and #2 work. It was just a matter who was getting the cleaner/better signal.


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## FullDuplex

There are actually 2 types of 3-way splitters - balanced and unbalanced. The balanced 3-way splitter has equal loss to the 3 outputs - about 5.5 to 6.0 dB for each. The unbalanced 3-way has one output with approximately 3.5 dB loss and two with approximately 7.0 dB loss. 

If an unbalanced is used, the 3.5 dB output usually feeds the modem.

There should be more than sufficient signal in most situations no matter which way you do it, however there are exceptions where the cable signal may be marginal.


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## crazyboy

Balanced 3 way splitter if you have a good enough signal coming in, if its a so so signal coming in then go for the 2-2ways.


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## RIVETER

duque00 said:


> Hey All,
> 
> Which of the following scenarios is correct.
> 
> 1) Line from pole to the house comes into a 3 way splitter. One for a Modem, the other 2 to cable boxes for HDTV's. No other splitters all feed direct from splitter to the individual devices.
> 
> 2) Line from pole to the house comes into a 2 way splitter. One for Modem, the other to another 2 way splitter which then goes to the cable boxes for HDTV's.
> 
> I said #1, my friend says #2 - which one is right and why?
> 
> Thanks in advance.


Bet him LUNCH.


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## StillLearning

#2 is correct no 2 ways around it 3way is an unbalanced splitter and can throw off the dbmv and in my experience 3ways expire quicker. Depending on my levels coming to the house I'd sooner use a 4-way with a terminator on one leg before i would use a 3way


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## wildleg

StillLearning said:


> #2 is correct no 2 ways around it 3way is an unbalanced splitter and can throw off the dbmv and in my experience 3ways expire quicker. Depending on my levels coming to the house I'd sooner use a 4-way with a terminator on one leg before i would use a 3way


interesting.

do you have any facts to support this ? 

why is dividing by 3 unbalanced, and dividing by 4 not ?

I would like to hear more on this.

I do know one thing, the comcast x1 cable boxes are extremently sensitive to any signal issues (db drop, reflection/crosstalk/interference), and work better with fewest splitters to the boxes. the central office could not hit the boxes properly with the hack wiring that I bought along with my florida house, and the cable guy actually went up in my attic and removed some splitters and split 4 ways at the drop to home runs in order to get them to work. surprised me.


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## Tqillya

I would say 2 is your best option. 
It really comes down to the signal that the modem is receiving. You want the upstream signal to be between + 8 to -8, the downstream between 40 and 50 and the signal to noise ratio should be in the mid 30 db's.
As strange as it sounds if the signal comes to the modem to high if causes the modem to reboot automatically randomly.


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