More Splitters or 1 large splitter

Discussion in 'TiVo Premiere DVRs' started by kturcotte, Jul 9, 2011.

  1. Jul 9, 2011 #1 of 16
    kturcotte

    kturcotte Active Member

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    Been having some cable signal issues on my Premiere for a little while now. Signal strength sometimes dips to around 30 db and high 50's, with some pixelation. I've attached a pic of my current setup. The cable goes into a 3-way splitter, which feeds a TW HD box, TW HD DVR box (Luckily I don't have to use the TW boxes lol), and then into another 3 way splitter, which feeds my modem/phone adapter, Premiere/Tuning Adapter, and another TW HD box. I'm wondering if maybe 1 large powered splitter might provide a better, more stable signal? I've also attached a pic of what that would look like. Ideas?
     

    Attached Files:

  2. Jul 9, 2011 #2 of 16
    socrplyr

    socrplyr Active Member

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    Just a quick little lesson on splitters that might help you fix your issues without using a powered amp (I try to avoid them, because sometimes they cause more problems than they help - but if used correctly they work fine). There is only one kind of splitter really, a 2-way splitter. When a 2-way splitter splits the cable, it sends about half the incoming power down each of the lines. Thus the power level is halved. To get a 3-way splitter, you daisy chain (internally) a second 2-way splitter on one of the outputs, which means it only has a quarter of the power. Thus, you will see the ports on the splitter labeled -3.5 dB (~half power), -7 dB (~quarter power), -7 dB (~quarter power).

    Since the outgoing power levels of the 3-way splitter are not equal and you want to do a split later down one of your lines, make sure that that line is connected to the -3.5 dB port on the first splitter. Also, since your Tivo seems to be having the problems and your other equipment isn't, I would at least try hooking the Tivo/Tuning Adapter combo up to the -3.5 dB port of the second splitter. This way the Tivo is getting pretty much the most power (and generally the best power) it can. I would also make sure that the splitters are decent quality, I have had some in the past that were terrible and swapping them out fixed my problems.

    If you do think you need to go the amp route, check with your local TWC on their policies as when I had problems they came out and put in an amp for free. This was because the signal coming in from the street wasn't good enough to be split. They didn't put in a combined splitter/amp, just a preamp before the splitter.

    Good luck,
    Josh
     
  3. Jul 9, 2011 #3 of 16
    socrplyr

    socrplyr Active Member

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    Two more things:
    Cables (and their connectors) can also sometimes be a problem, so make sure they are all a decent quality, especially your "trunk" line and ones going to the Tivo.
    A larger splitter at the beginning could help as there are addition losses from every transition and connector, but if everything is decent quality then you shouldn't see much change. This is because internally build connections inside a splitter should be more solid than stringing them together with cables. Again though these issues with decent stuff typically are negligible.
     
  4. Jul 9, 2011 #4 of 16
    aaronwt

    aaronwt UHD Addict

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    WOrst case try the amp. If it doesn't work just return it for a refund. Just make sure it is a two way amplifier.

    My brother uses one with Comcast with no issues. Although I don't know where he got his from. I have FiOS which is a hot signal so I don't need any amplification. I have an an eight way splitter, plus with the internal TiVo splits I still have signal strength to spare.
     
  5. Jul 9, 2011 #5 of 16
    rabinny

    rabinny New Member

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    With all due respect, none of what you just wrote is true. Where he connects his TiVo to the splitters has everything to do with how much power he is starting out with in the first place. 2-way splitters do not cut the power in half and 4-way splitters do not give you 1/4 power. Sorry dude.

    If you are starting out with a +8 on qam at the side of your house and you hit a 3-way splitter you will loose the signal designated on each splitter leg. So if the line that is feeding the second splitter is coming off of the -3.5 db leg then you will loose that much which will give you a +4.5 db of power left. You also loose power depending on the length of the wire. If the Tivo is on the -7db leg of the second splitter then you will have around a -3db at the TiVo calculate in signal loss according to length of wire and you will most likely end up with around a -6db at the TiVo. Once you dip below -10db at your device you will start to see problems. If the wires in your house are old, like RG59 wire, then you might be looking at something more like a -12 at your TiVo.

    I wouldn't change which leg your TiVo is connected to at the second splitter because that may impact your modem performance. TW probably set it up that way on purpose.

    I'm getting a headache. ;) Call TW and have them send a tech out before you start changing things around. :D
     
  6. Jul 9, 2011 #6 of 16
    tomhorsley

    tomhorsley Well-Known Member

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    Splitters can have quality problems as well, and if there are cable modems involved, you might need special 2-way splitters (depending on where cable modem is in the layout). I had a really rotten signal till I replaced an old splitter with a new fancy one from Radio Shack which I almost certainly paid way too much for, but which really did provide much higher quality signals on the output side.
     
  7. Jul 9, 2011 #7 of 16
    L David Matheny

    L David Matheny Active Member

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    Actually I thought his explanation was pretty good, except as I recall it's voltage that gets divided by half (roughly) in a splitter. I think a two-way splitter gives you (ideally) half the voltage (signal strength) and one quarter the power at each output. And it's been my understanding also that a three-way splitter is indeed a two-way with another two-way on one of the outputs, giving one -3.5dB output and two -7dB outputs.

    As you said, it is also important as a practical matter to configure the splitters based on how much signal is available to start with. And if there isn't enough to start with, a distribution amp (powered splitter) might be needed.
     
  8. Jul 9, 2011 #8 of 16
    socrplyr

    socrplyr Active Member

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    Everything you said there is right, but nothing you said disagreed with what I said. Half power in decibles (dB) is a reduction of -3.01 (10*log(0.5)). In a splitter the remainder to get to -3.5 dB is due to connector/resistive losses, but for simplicity's sake you can just think of it as half the power. By the same token -7 dB equates to quarter power 10*log(0.25)=-6.02 with the extra losses makes it near -7 dB. Basically if you have some power coming in and you split it once, then the sum of the powers coming out can at most be the amount of power coming in. Splitters split power evenly, so it must then be halved.

    I also agree with your assertion that there can be losses in the cables (that is why I made my second post earlier). In addition ever connector or coupling has loss as well. In general however theses losses are relatively small compared to the drop in power due to splitting if the cables are of decent quality or the runs aren't really long.

    I was only trying to point out to the OP that he/she might be able to get the needed signal power to have a high enough SNR by just rearranging the connections such that it balances things out. Without some special equipment he/she would not be able to measure the loss due to any one cable or connector, but it is simple to compute the reduction in power caused by the dominant factor, the splitter. Depending on the connections used the difference in power could be up to 4X. In reality, if the OP's cabling and splitters are good, then making 3 separate runs to the devices would not help the signal problems very much. The lines would still need to be split just as many times causing the same reduction in power as before, it would just be happening in a different place. If the cabling and splitters are good, there is no need to run the multiple lines like the OP suggested just add the amplifier before the first split and be done with it. Note that an amplifier typically boosts power by 15 dB, which is equivalent to 4 splits in a row or so (-3.5*4=14 dB).
     
  9. Jul 9, 2011 #9 of 16
    socrplyr

    socrplyr Active Member

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    Thanks for the support :). You are correct except for the voltage being halved. There is conservation of energy (and therefore power which is energy per time). Voltage is proportional to the square root of power, so voltage is multiplied by the square root of 1/2 or 0.707.

    I definitely agree with you and rabinny that the OP needs to configure the splitters correctly, thus why I suggested the setup that I did as it would be an acceptable configuration. The max splitter loss with his setup should be -10.5 dB. There is no splitter setup that could prevent that much loss to at least two TVs. Even if the OP bought a combined amp with splitters, then the amp would give +15 dB (or so) and then split down. If it was a 8-way split it would net +4.5 dB for each port. That is the same as just adding a standalone amp before the first split. Now like I said there are some losses from things not being integrated. If those losses are more than the +4.5 dB gain, then you have a cabling problem and that would need taken care of anyways. If the losses are less than +4.5 dB, and you still have problems, then the issue is the cable feed to your house most likely. Those losses aren't really calculable without equipment to measure your actual wiring. Typically, you just try swapping out cables and splitters with known good ones.
     
  10. SNJpage1

    SNJpage1 Well-Known Member TCF Club

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    I disagree with how the explantion of the splitters is going. If you look on the housing of a good splitter it will tell you the DB insertion loss. That is all you need to work with. I have Comcast and a lot of 100 foot cable runs in the house. I bought an 8 db
    bi- directional amp with 8 ports. I have terminating plugs on the two ports I don't use. It works great. Even the techs from Comcast who have done repair work at my house have commented about how it is the best arrangement for doing the job.
     
  11. socrplyr

    socrplyr Active Member

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    What about the discussion do you disagree with? With quality components, you will see little difference between the two setups... If Comcast would have set it up for you they wouldn't have opted for the method you did, because it costs more and has little benefit. I am really just trying to suggest something to the OP that has the needed effect and doesn't require running many cables and buying costly equipment. Now if I were setting up a new house and the incoming signal from the street was low and needed boosted, yes I would have opted more for a method like yours. The real issue is that the OP has 3 devices near only one cable outlet. If each one had their own homerun line things would be different.
     
  12. SNJpage1

    SNJpage1 Well-Known Member TCF Club

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    What I was commenting about was to find the way to do it. Forget about trying to figure if you lose half or 3/4 of the of the power. To some this is too complicted. Just go by the db loss of the splitters which is writen on most of them. You want the lowest DB insertion. If one spliter is rated at 4 db loss and another is 7 db then go for the 4. On some 4 way splitters 3 ports might be rated at 7db and a 3rd at 4 db. If you are going to add more splitters down line then put them on the 4 db port. The higher the db number you end up with the more loss there is.

    Now before going thru all of that I would suggest first checking the ends on all the cables. It only takes one bad crimp to cause problems. Personally I do not trust twist on connectors and will only use crimp ones with compression ones as a second choice.
     
  13. rabinny

    rabinny New Member

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    :confused:


    An 8 port anything will destroy your return signal for your other devices. I hope your modem is not coming off of that 8 port amp.
     
  14. SNJpage1

    SNJpage1 Well-Known Member TCF Club

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    My cable modem comes out of a 2 way splitter before the 8 port. One port feeds the modem the other port feeds the 8 port bi directional amp. However, my Tivo HD and two comcast DVR's work with out any problems going thru the amp.The cable modem was working thru the amp with out any problems but the Comcast tech said it would be better to have it ahead of the 8 port and he gave me the 2 way splitter and made up the short jumper cable.
     
  15. rabinny

    rabinny New Member

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    Very nice. You must be starting out with some pretty good return power or transmit power. If you were starting out with around a +42 at the side of the house and it hit that 8 port amp your transmit power would jump to about +53 which could cause some modem and on-demand issues. :up:

    You must be starting out with around +36
     
  16. SNJpage1

    SNJpage1 Well-Known Member TCF Club

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    After some inial problems Comcast did a lot of rewiring in my neighbor. They use fiber from their center to about 1 mile from my house where it then converts to coax. All new coax on the last 1 mile and new coax to each house was done about 4 years ago. Everything in my house is quad 6. So the signal is high to start with. A Comcast tech gave me a selection of inline attenuators incase I had problems but never needed them.

    Having worked as a Verizon tech I was friends with a lot of the Comcast techs and was able to get a lot of help in my set up from them. Thir biggest piece of advice was making sure the connectors were crimped correctly. Bad crimp can cause ground problems which cause interference in the signal. A lot of people think their signal coming into the house is no good when infact it is a bad crimp.
     

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