1x2 + 1x3 Split - AVS Forum
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post #1 of 20 Old 02-17-2012, 11:59 AM - Thread Starter
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Comcast came in December to upgrade my cable to Digital HD, Internet and Digital Voice. My old layout was a 1 x 3 splitter feeding 2 TV's and a VCR as home runs. The Comcast guy adds a 1x2 splitter, feeds the Internet/Phone modem off one leg and the 1x3 for the TV's/VCR off the other leg. Lately one of the TV with a Cable Card has lost some channels. I am wondering if I wouldn't be better off with a straight 1x4 splitter as it seems to me the TV's would get more signal and the internet/phone still enough. I believe I start with about 13 db of signal at the entry point.
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post #2 of 20 Old 02-17-2012, 01:09 PM
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Starting out with +13 at the point of entry is a good solid number. Any configuration for what you have will work for all devices.

Cablecards are a funny monkey. There is a sub band freq that they get their authorization from that likes to be in a sweet spot. Are you missing authorization or are the channels tiling?

If either I would just double check tight connections, have clean fitting wells ( the area around the center conductor etc) and see if maybe a bad connection was made.

Signal wise you should be good to go assuming no outlet is over 150' or so.


A single splitter would be ideal in this case as long as your modem stats , especially the return, can take a few extra dB.

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post #3 of 20 Old 02-17-2012, 02:24 PM
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Best bet is that if Comcast performed the installation and configuration change(s), call them to remediate.

If you only have a "problem" with one TV that lost channels... unplug the TV from power for a few minutes. After power up, re-perform a channel search/scan.
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post #4 of 20 Old 02-20-2012, 07:40 AM - Thread Starter
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Thanks to you both for the ideas. Will pursue both. Much obliged!
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post #5 of 20 Old 02-20-2012, 08:00 AM
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And as far as what they did, putting a splitter first in-line for the cable modem is standard practice. Cable modems are much more picky about a strong signal than cable cards. You can certainly try putting a 1x4 in it, and see if the cable modem still holds a steady bandwidth. But like the above poster said, if Comcast did it, just call them out and have them troubleshoot.
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post #6 of 20 Old 02-20-2012, 08:40 AM - Thread Starter
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...and now this morning the signal is back on those missing channels all by itslef. On another TV leg I have a PC with cable tuner (Ceton) that uses a card and it was showing -2.5 db of signal which is a long way from 13, so I think I will at least try the 1 x 4 split for the small bucks it will cost, then if I continue to get problems on the set that was acting up, call in Comcast.
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post #7 of 20 Old 02-21-2012, 04:27 AM
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Quote:


TV leg I have a PC with cable tuner (Ceton) that uses a card and it was showing -2.5 db of signal which is a long way from 13,

That level is fine don't know how accurate that reading is but it is near the sweet spot.
As a test (if you have a laptop) I would move the modem to that spot and connect it to the laptop go into the diagnostic screen of the modem (type 192,168.100.1 into your browser) look at the levels tab and see what your upstream power is.
Then put everything back.

But more than likely your levels are fine.
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post #8 of 20 Old 02-21-2012, 05:28 AM - Thread Starter
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Thanks RC - I botched the signal number I am afraid. The Ceton tuner device (worst of its 4 tuners) was not -2.5, but -4.5. It was also getting knocked off line occasionally. I moved its coax feed to be at the first split and got +2.4 db. It is no longer falling off line and the phone/internet modem is living ok off the -4.5 location so far. My sense is that if I put in the 1 x 4 splitter I will have pretty good balance all around maybe about 0 db all taps.
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post #9 of 20 Old 02-21-2012, 05:59 AM
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Just to make sure we're on the same page.

To confirm the setup:
1) One 2-way at entry. One feed to cable modem, the other to a 3-way splitter
2) The 3-way outputs to 2 tuners (TV) and a VCR.

Your assumptions are to remove both the 2-way and 3-way splitters and replace with a 4-way. If that's correct, here are some thoughts to ponder.

A 2-way has -3.5dB loss on each leg.
An unbalanced 3-way has -3.5 on one leg and -7 dB on the remaining two.
A 4-way is -7dB on all ports.
It is usually best to have the cable modem on the 1st 2-way split (for signal/performance).
Typically the longest coax run is connected to the -3.5dB port of the 3-way (verify that this in your setup).

If you do have an unbalanced 3-way splitter, have you thought about leaving the 2-way and replace the existing 3-way splitter with a "balanced" 3-way (-5.5 dB all ports)? It may be better in the long run (no pun intended).
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post #10 of 20 Old 02-21-2012, 06:24 AM - Thread Starter
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Ratman - You have the basic set up correct. The 3 way actually feeds 2 TV's and an HTPC (Formerly a VCR) with a Ceton Infinitv4 Tuner. TV 2 probably has the longest run, about 55 feet, with TV 1 a close second. The HTPC is probably 45 feet. All hoem runs and RG6 Quad I think. The Comcast cable/phone modem is about 30 feet. TV 1 is served by an SA Cable box and has suffered no signal issues. TV2 had the loss of signal on some channels, but came back by itself. The Ceton had the -4.5 db of signal and was dropping off line daily. Since it is now stable for 4 days I am suspicious soft signal was the problem (though mfg says -10 to +10 is ok), though more time must pass to confirm.

I was not aware that there are balanced and unbalanced splitters so your info was very helpful in that regard. I have the 4 way splitter still in its package so can return if you think that is not the best way to go. With the above new info I provided, if you can confirm how I might better set up the splitters and recommend a model to buy (not sure local places have the special splitters), I would be much in your debt. Doing your math, I wonder if I really still have 13 db of signal to start with.
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post #11 of 20 Old 02-21-2012, 07:12 AM
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FWIW your Ceton has a splitter built in. 4 tuners? 4 way split.


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post #12 of 20 Old 02-21-2012, 07:49 AM
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1st... confirm they type of 3-way splitter currently installed.

Math:
replace both 2 and 3 with 4-way... -7dB all ports (plus loss over distance)

Leave 2-way, -3.5dB to each leg. One for tuners, one for modem (best to keep least loss to modem is suggested).

Using existing setup (assuming unbalanced 3-way):
-3.5 for first split, -3.5 for longest run = -7dB
-3.5 ..... -7 for remaing two = -10.5 dB

Using 4-way = -7dB for all runs. Caveat... may not be best for cable modem.

Using 2-way and balanced 3-way:

-3.5dB for first split (one to cable modem, remains "as is")
-5.5 each port = -9dB (for Tuners)

Note:
If Ceton is always and only problem, olyteddy makes a good point.

Balanced splitter:

http://www.amazon.com/Antronix-CMC20.../dp/B001E4PZPQ
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post #13 of 20 Old 02-21-2012, 08:18 AM - Thread Starter
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Quote:
Originally Posted by Ratman View Post

1st... confirm they type of 3-way splitter currently installed.

Math:
replace both 2 and 3 with 4-way... -7dB all ports (plus loss over distance)

Leave 2-way, -3.5dB to each leg. One for tuners, one for modem (best to keep least loss to modem is suggested).

Using existing setup (assuming unbalanced 3-way):
-3.5 for first split, -3.5 for longest run = -7dB
-3.5 ..... -7 for remaing two = -10.5 dB

Using 4-way = -7dB for all runs. Caveat... may not be best for cable modem.

Using 2-way and balanced 3-way:

-3.5dB for first split (one to cable modem, remains "as is")
-5.5 each port = -9dB (for Tuners)

Note:
If Ceton is always and only problem, olyteddy makes a good point.

Balanced splitter:

http://www.amazon.com/Antronix-CMC20.../dp/B001E4PZPQ

Got all that now. Thanks. Not sure what olyteddy's point was other than each Ceton tuner is getting a split of a split of a split and that is a lot. Looks like I may have to try some of the options to see what works best. Would like to avoid signal boosting route if possible, imagine you would agree.

Much appreciate your thinking.
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post #14 of 20 Old 02-21-2012, 10:49 AM
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Quote:
Originally Posted by sgbroimp View Post

Not sure what olyteddy's point was other than each Ceton tuner is getting a split of a split of a split and that is a lot.

That is exactly the point.
One physical coax (broadband) feed to accomodate the 4 Ceton tuners. The incoming signal gets "split" (divided) between the 4 tuners. So... essentially, an additional -7dB to each tuner.

I'm am not saying this is "how" the Ceton card/tuners work, but is an assumption and something to be taken into consideration.

A distribution amp after the 2-way splitter (for the video feeds) may be a solution after you do some initial testing.
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post #15 of 20 Old 02-21-2012, 11:44 AM - Thread Starter
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Quote:
Originally Posted by Ratman View Post

That is exactly the point.
One physical coax (broadband) feed to accomodate the 4 Ceton tuners. The incoming signal gets "split" (divided) between the 4 tuners. So... essentially, an additional -7dB to each tuner.

I'm am not saying this is "how" the Ceton card/tuners work, but is an assumption and something to be taken into consideration.

A distribution amp after the 2-way splitter (for the video feeds) may be a solution after you do some initial testing.

Yes, one can only split a pie into so many pieces until nobody eats much at all. Will start tonight when I go home to assess the type of 3 way splitter I have and then follow your good guide from there.
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post #16 of 20 Old 02-22-2012, 05:05 AM - Thread Starter
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Well, it turns out that the 3 way is an Antronix unbalanced (2 x 7, 1 x 3.5), witht the 3.5 feeding the STB. Unfortunately, last night, even with its signal now strenghtened to +2.5 db, the Ceton 4 way tuner went down again last night (cancels its USB connection), so signal is maybe not my problem afterall.
Nothing is simple.
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post #17 of 20 Old 02-22-2012, 07:23 AM
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Not quite clear, but did you connect the Ceton coax to the -3.5dB port and it still failed?
If so... you may have a Ceton or PC issue.
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post #18 of 20 Old 02-22-2012, 07:44 AM
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Quote:


cancels its USB connection

???? That probably has nothing to do with signal strength. Sounds like a driver or software issue.


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post #19 of 20 Old 02-22-2012, 08:03 AM - Thread Starter
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Quote:
Originally Posted by Ratman View Post

Not quite clear, but did you connect the Ceton coax to the -3.5dB port and it still failed?
If so... you may have a Ceton or PC issue.

Yes, the Ceton is now at the very first 2 way splitter, -3.5. It is getting plenty of signal that way, +2.5 db or so all 4 tuners. Yes, there is most likely a Ceton or PC/Win7 issue. Others are having the same problem with the USB version of the Ceton, but it seemed prudent to assure that weak signal was not a cause. Overheating (these run hot) is another possibility and I just last night moved the unit where it will run cooler so we will see if that brings anything. I think in the end a Ceton firmware update is going to be the answer. The tuners (all each time) should not be simply disappearing. Funny is the fact that a 5 second power off of the Ceton and then on resets things, with usb chime at disconnect and reconnect.
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post #20 of 20 Old 02-22-2012, 08:31 AM
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And... with that, perhaps you should seek advice in the HTPC forum.
http://www.avsforum.com/avs-vb/forum...aysprune=&f=26
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