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Signal shortage question for xfinity techs

Frequent Visitor

Signal shortage question for xfinity techs

 

Xfinity tech came over the weekend to install a box to my basement TV. But by doing this he says the signal loss is over the max allowed -8db. He said that my internet will go in and out of service all the time. Please see attached diagram. Before he came I just had the outside line coming into the house through the mechanical room connected with a barrel connector that led up to the attic into the amp. That set up was perfect and didnt suffer from signal loss. I was at -5.8db. After the he connected the basement TV with a splitter in the mechanical room I was at -10db.

 

The proper set up is if I was able to take my cable feed from my basement up to the attic and then plug into the amp. This can not be done.

 

Any other ideas. Can I use an amp in the mechanical room also?

 

 

 

 

 

Gold Problem Solver

Re: Signal shortage question for xfinity techs

That first splitter is really messing things up but quite honestly the set up should be working.

Sounds to me like you are not getting a strong enough signal coming into the house. What were the signal levels at the line in, before the splitter?
Frequent Visitor

Re: Signal shortage question for xfinity techs

Thanks for your response. I was at -5.8db before the splitter was added in the mechanical room to accommodate the cable wire from the basement TV.

Gold Problem Solver

Re: Signal shortage question for xfinity techs

5.8 before the first splitter is too low and should be corrected.
Frequent Visitor

Re: Signal shortage question for xfinity techs

That's what I thought. I mean 3 TV's and a modem/router with an amp and i'm  at -5.8db doesnt sound right. I could understand this reading if I didn't have the amp.

Silver Problem Solver

Re: Signal shortage question for xfinity techs

Here is the basic splitting rule. The first splitter is a 2 way, which you have. One side goes to the modem, the other side goes to everything else.

Try that.

Frequent Visitor

Re: Signal shortage question for xfinity techs

Without the basement TV I just have a barrel connector connecting the outside line and the line feeding all the way up to the amp in the attic. With that set up no 2 way splitter was needed in the mechanical room and I was at -5.8db. I need that 2 way splitter now to plug in the cable line coming from the basement TV and the other slot is to coonect main line running up to the attic.

Gold Problem Solver

Re: Signal shortage question for xfinity techs

In the grand scheme of things it does not matter if one leg of the two splitter is connected to a modem or a cable box location.

The setup should work there just isn't enough signal getting up to the house and therefore up to the amp.
Official Employee

Re: Signal shortage question for xfinity techs


RickGr4 wrote:
In the grand scheme of things it does not matter if one leg of the two splitter is connected to a modem or a cable box location.

The setup should work there just isn't enough signal getting up to the house and therefore up to the amp.

How hard would it be to drop a cable outlet from attic to basement? That would eliminate the need for the first 2 way splitter and keep everything in spec.

 

Is the basement TV going to have an X1 box?




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Frequent Visitor

Re: Signal shortage question for xfinity techs

I thought of that. It's very hard to do. No way to fish a wire down. I have an HD box but it's not an X1 box.
Official Employee

Re: Signal shortage question for xfinity techs

You posted in the X1 forum that's why I wanted to make sure. If it's a legacy box or DTA that's going in the basement, you can put another commscope like the one that's in the attic and it will take the place of the 2 way splitter.



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Frequent Visitor

Re: Signal shortage question for xfinity techs

I agree with you. 4 TV's and one router. Xfinitys best amp and one 2 way splitter and I'm already at -10db's. I think the signal going to the house is low.
Official Employee

Re: Signal shortage question for xfinity techs

-10 db isn't out of the question, you are losing a lot of signal over distance and is the interior cable RG6 or RG59. Per your diagram, your cable goes up to the attic and comes right back down. To get an accurate reading of what's coming in the house, hook up your modem to the line coming in the basement and get your signal levels there. 




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Gold Problem Solver

Re: Signal shortage question for xfinity techs

Yes Andrew brings up a good point. You are losing signal over the long run from the splitter up to the attic. If that run is anything less than RG6, that is a real problem. In a perfect world, that run should be RG6Q at a minimum.
Frequent Visitor

Re: Signal shortage question for xfinity techs

I have an X1 box in the family room, but the basement TV is a small HD box. But it does not have DVR and I pay like $5 a month for it only. The guide is also different then the rest of the TV's. I think its a DTA box. This sounds like a good plan.

Frequent Visitor

Re: Signal shortage question for xfinity techs

Not sure if I have RG6 or RG59. But my main line goes up to the attic but it then plugs into the amp in the attic. It doesn't come back down. The basement TV cable is all alone entering the mechanical room. Should be going to the attic but it isn't.

 

I have a tech coming tomorrow. First request would be to test the signal coming into the house.

 

Regular Contributor

Re: Signal shortage question for xfinity techs

Install a standard 1-out drop amp in the mechanical room, with a DC-12 (12dB TAP) on the output.  The TAP leg goes to the basement TV, while the OUT leg goes to a 4-way splitter in the attic, which then feeds the other 4 outlets (3 TV and cable modem.


CIAO!

Ed N.
CATV.jpg
Gold Problem Solver

Re: Signal shortage question for xfinity techs

Interesting idea Ed but I am guessing the configuration you are suggesting would have upstream issues (possibly severe) unless an X1 spec amp is involved.

Personally I would want to know why the OP isn't getting more signal from the street...

Also I am very concerned about the quality of cable he has running from bottom to top. An RG 59 would probably be inadequate.
Silver Problem Solver

Re: Signal shortage question for xfinity techs

Never run the modem from the amp. And the amp should be at the beginning on 1 side of a 2 way. Putting the amp down the line just amplifys line noise.

Rick is right, fix the street signal first.

Regular Contributor

Re: Signal shortage question for xfinity techs


RickGr4 wrote:
Interesting idea Ed but I am guessing the configuration you are suggesting would have upstream issues.

Actually, Rick, the current configuration loses ~1dB more than the proposed configuration would (for the outlets upstairs.  The basement would see ~8.5dB increase in loss).  All outlets would be fairly equal in signal levels.

 

I agree, though, figure out why the incoming signal is low first.

 

I know people say that Series 59 cable can't be used.  If a cable is swept to 1Gig, it's swept to 1 Gig.  As long as the cable in use has a bonded foil shield and aluminum braid, 59 is good to go in most houses.  A floor is what, 9' in the typical house.  From basement to attic in thOP's house is ~18 vertical feet.  We know it's not a straight shot, so we'll say the cable is 30' end-to-end.  Series 59 cable loses a whopping 0.4dB more (@750MHz) than does Series 6 cable.


CIAO!

Ed N.
Regular Contributor

Re: Signal shortage question for xfinity techs


barbie123 wrote:

Never run the modem from the amp.


Which is an excellent rule of thumb.  Fortunately, it's a rule of thumb and not an absolute rule.  If the configuration of the cabling within the home gives you no choice but to place the cable modem after an amp, that's the way it is.

 

It would be nice to know what the OP's signal levels are at his cable modem, which he can probably see at 192.168.100.1  I would be really interested in downstream power, upstream power, and SNR


CIAO!

Ed N.
Frequent Visitor

Re: Signal shortage question for xfinity techs

Just an update. Tech said there is an issue at the pole outside. Low signals getting into the house. Engineer is comming out to service the issue. Thanks so much everyone for your responses!
Silver Problem Solver

Re: Signal shortage question for xfinity techs

Let us know when that actually happens. I had to wait over a year, and made dozens of calls to get that done. 

Frequent Visitor

Re: Signal shortage question for xfinity techs

Wow thats a long time. I will update you.

Service Expert

Re: Signal shortage question for xfinity techs

It took Comcast two weeks to resolve the similar issue in my alley; it was at some kind of "head-end" on a pole at the end of my alley.




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Official Employee

Re: Signal shortage question for xfinity techs

Hello acblue94,

 

 Just curious, did the technician happen to say if you were at the end of the line (meaning you are off the last tap)? How long is your drop? Is your drop underground, or aerial? Technically an amp is not needed unless your drop is like 200 - 300 feet, or maybe and I stress maybe, you're off a 8 value 4 port / 2 port tap. As a former line tech, I would see most of the times there is an issue with the drop. I worked in the mountains here in Denver and with squirrel chew and drops spanning 200 + feet, it would really cause issues.  If you would like me to look at your account I can. Can you verify your account information with me? I would need your account number, full name, and service address. You can private message me by clicking my name and clicking private message. Thank you




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Regular Contributor

Re: Signal shortage question for xfinity techs


ComcastShane wrote:

Technically an amp is not needed unless your drop is like 200 - 300 feet...

Not quite accurate.  The FCC says no less than 0dBmV at the terminal, which is the settop box (TV set)(47 CFR 76.605(3)).  Say you have +15dBmV at the tap and a house that is 50' from the tap, then another 25' in to the 8-way splitter.  At 750MHz, you'd be looking at -2.35dBmV at the outlets, which is below the level the FCC requires.

 

While amplifiers are used to for really long drops, more often than not an amplifier is used to compensate for the splitter loss in feeding multiple outlets.

 


CIAO!

Ed N.
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