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tshirt
Premium Member
join:2004-07-11
Snohomish, WA

tshirt to HunterZ

Premium Member

to HunterZ

Re: [Signals] Just moved and need some advice

Yes having a Amp on the cable line is a bad idea, even a really good amp (like comcast would install as a last effort)would introduce some noise, and might intfere with the return signal

Yes Comcast should be able to fix it

Probably noise/problems maintaining sync

channel changes can happen any time, and signal constantly fluctuate somewhat, if yours is going beyond normal or the amp is injecting noise you may have huge numbers of resends or other problems
If you posted the log we might see some indications of what but I thing you need a tech visit to get even close to good.

HunterZ
join:2003-07-16
Kent, WA

1 edit

HunterZ

Member

said by tshirt:

If you posted the log we might see some indications of what but I thing you need a tech visit to get even close to good.

Comcast's SB6120 firmware seems to disable/redirect most of the useful logging. All I have are some old, useless boot-up messages:
Jan 01 1970 00:00:18 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=3c:75:4a:75:5c:f7;CMTS-MAC=00:1d:70:cc:4e:3e;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:12 6-Notice Cable Modem Reboot from SNMP ;CM-MAC=3c:75:4a:75:5c:f7;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:18 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=3c:75:4a:75:5c:f7;CMTS-MAC=00:1d:70:cc:4e:3e;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:12 6-Notice Cable Modem Reboot due to power reset ;CM-MAC=3c:75:4a:75:5c:f7;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:18 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=3c:75:4a:75:5c:f7;CMTS-MAC=00:1d:70:cc:4e:3e;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:12 6-Notice Cable Modem Reboot due to power reset ;CM-MAC=3c:75:4a:75:5c:f7;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:22 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=3c:75:4a:75:5c:f7;CMTS-MAC=00:1d:70:cc:4e:3e;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:12 6-Notice Cable Modem Reboot due to power reset ;CM-MAC=3c:75:4a:75:5c:f7;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
said by rody_44:

Any chance you can put the modem where the amp is and get the levels there. That way we will probably know if the problem is inside the house or out on comcasts end.

Well crap! I'm glad you suggested that, because that gives me -4 to -5 dBmV down (with 36-37 dB SNR) and 40 dBmV up. Running speed tests, I am getting 14-15mbps down (ouch, what happened there?) and consistently over 5.5mbps up (wow!).

Previous owners of the house must have either used some low-quality cable in the mere 20-30 foot run to the family room, or else there's a second hidden splitter along the way besides the one I bypassed outside the garage. I'll take a look and see if I can trace the line. Unfortunately I think it may run inside of the shared wall between the garage and family room, then through a hole in a full-wall built-in entertainment center / shelving system (EDIT: Actually it probably runs under the crawlspace or something, likely with a female-to-female extender or splitter somewhere since the cable looks completely different on the side of the house versus the family room).

The downstream power level is still a bit low even when connected directly, though, especially since I do need to add a 2-way -1.5dB splitter to get both TV and Internet service. I expect that this would result in -5 to -7 dBmV; is that still a worrisome number? I would not want to use the amplifier in that configuration, as I've heard that the SB6120 doesn't like +10dBmV or higher.

I'll try to take some pics with my phone once it has charged up a bit. For now, here is a pic I took of the amp in the garage in case anyone is interested: »docs.google.com/open?id= ··· RSFFuQzQ

plencnerb
Premium Member
join:2000-09-25
53403-1242

plencnerb

Premium Member

I take it the line that is in your garage is the "main" line into your house? You don't specifically say that, but by what you said, I think my guess is true.

I would see if there is a way to trace your line, as it does appear to either be added splitters going in, or maybe even some loose-fitting connections. It could also be (as you said) bad coax too.

Finally, when I went to look at the picture you linked of your amp in the garage, I don't get a picture, but a video and an ad page for Google Drive. Am I missing something?

--Brian

ropeguru
Premium Member
join:2001-01-25
Mechanicsville, VA

ropeguru

Premium Member

Click for full size
Worked fine for me. Here is the pic.

HunterZ
join:2003-07-16
Kent, WA

1 edit

HunterZ to plencnerb

Member

to plencnerb
said by plencnerb:

I take it the line that is in your garage is the "main" line into your house? You don't specifically say that, but by what you said, I think my guess is true.

So the main line from Comcast comes out of the ground outside of the garage, and has what appears to be a foam cylinder around part of it that says "AMP" (must be a brand name since it's not related to the amplifier). This wire goes into a hole in the side of the house that leads straight to the garage.

In the garage above the hole, that cable enters the top right of the amplifier. The top left is the power input from the wall wart, and the bottom is the amplified output.

The amplified output cable goes back out the same hole to the outside, and originally went into a 3-way splitter mounted to the outside of the house. I bypassed this with a GE/Jasco female-to-female coax connector (aka "double F jack") so that only the cable to the family room was connected.

The family room, office and 1 undetermined cable go back into the same hole in the side of the house, but instead of going into the garage they disappear completely. I suspect they go down into the crawl space. All cables are black (as far as I can tell, since they got covered in tan house paint at some point) and have F connectors on the ends outside the house that appear to have been installed by Comcast at some point. Inside the house, all of the F connectors are a different style; I will try to post pictures later when I get a chance.

In the family room, about 10-15 feet of white coax comes out of a hole in the wall (yes, white, even though outside the house the corresponding cable is black). I can see yellow insulation in the hole. I tried tugging on the white coax cable, but it seems quite secure inside the wall.
said by plencnerb:

I would see if there is a way to trace your line, as it does appear to either be added splitters going in, or maybe even some loose-fitting connections. It could also be (as you said) bad coax too.

I'm not keen on spelunking my crawlspace. Anyone know how much Comcast might charge to run 25-30 feet of high-quality cable across a crawlspace between two pre-cut holes?

In other news, I moved the cable modem back to the family room, re-activated the amplifier, and hooked up a Comcast-supplied 2-way splitter in the family room so that I could also connect the TV. The cable modem is now showing exactly 0 dBmV on all 4 downstream channels, plus 46 dBmV upstream. I suspect that previous residents installed the amplifier (or had Comcast install it) and worked with Comcast to tune the connection without knowing that the house wiring has problems.

Edit: Here are some more pics:
- Cable situation outside of the wall that the amplifier is on (blue tape is my attempt to label that cables): »docs.google.com/open?id= ··· WVmNuYWM
- Temporarily bypassing the amplifier with a GE/Jasco "double F jack": »docs.google.com/open?id= ··· rTzZudUU
- Family room cable, to which I have connected to a Comcast-supplied 2-way -1.5 dB splitter for the Internet and TV service: »docs.google.com/open?id= ··· 1OC1CQjA
- Family room cable coming from hole in wall/built-in cabinet: »docs.google.com/open?id= ··· tenRTcXc
HunterZ

1 edit

HunterZ

Member

Update: With cable -> amp -> family room -> 2-way splitter -> modem and TV, I am consistently getting around 20 mbps down and 5+ mbps up. This is as good of performance as I was getting when connected directly to the line in the garage. I guess being able to bond 4 channels down and 2 up is enough to make up for needing the amplifier to reach 0 dBmV (which is exactly where the downstream power level is at).

I think I'm going to live with the connection as-is for now, since I don't expect to be able to get better performance from correcting it. I will continue to monitor stability and speed, though.

ropeguru
Premium Member
join:2001-01-25
Mechanicsville, VA

ropeguru

Premium Member

What you really need to do is get a truck roll and have Comcast come out and get the ball rolling to get the levels adjusted without the AMP.

HunterZ
join:2003-07-16
Kent, WA

HunterZ

Member

Is it normal for house wiring to cause a -8 dBmV drop? Since I'm getting -4 dBmV at the line from Comcast, I'm concerned that they're going to blow me off by saying that that is good enough and that the house wiring is my problem.
rody_44
Premium Member
join:2004-02-20
Quakertown, PA

1 edit

rody_44

Premium Member

No -4 isnt normal. But we still dont know the actual signal. I believe that thing marked Amp is nothing but a splice connector. Open that up and that is where the actual comcast signal would be. Thats if im reading the picture correctly. Its not out of the question that a piece of bad coax only a few feet long loses 15 dbs. Even the piece as short as the one going from outside to iinside your garage. The piece at the outside is what is important in comcasts eyes.
rody_44

1 edit

rody_44 to HunterZ

Premium Member

to HunterZ
The cable both in your family room and at the amp in the garage look to me like some premade cables you buy at a home improvement store judging by the ends. All the cables outside have ends that would be typical of cable company installed cables. So im guessing all your cables are homeowner installed and the cable company simply put ends on the ones outside. I dont see your cable bonded at all. Not good, especially with a modem.

HunterZ
join:2003-07-16
Kent, WA

HunterZ

Member

said by rody_44:

I believe that thing marked Amp is nothing but a splice connector. Open that up and that is where the actual comcast signal would be.

I'll try to do that when I get a chance. I did take a closer look and found that it is actually a hard plastic case that may not be easy to open, as it appears to snap together with tabs. It doesn't look like opening it will be as trivial as I'd hope.
said by rody_44:

Its not out of the question that a piece of bad coax only a few feet long loses 15 dbs. Even the piece as short as the one going from outside to iinside your garage. The piece at the outside is what is important in comcasts eyes.

As I mentioned before, I get power levels of -4 dBmV just inside the garage, so I'm likely not losing more than 4 dB in the couple of feet between the splice and the inside of the garage. I definitely want to check what signal levels I can get at the splice, though.
said by rody_44:

So im guessing all your cables are homeowner installed and the cable company simply put ends on the ones outside.

This was my guess as well; it's good to get confirmation.
said by rody_44:

I dont see your cable bonded at all. Not good, especially with a modem.

I would have expected at least the splitter to be grounded, but it isn't. The "Amp" case is lashed to the telephone conduit with a plastic zip-tie, and is not electrically connected to the conduit or anything else as far as I can tell.

My house electrical mains come from underground, and connect to the meter box via a conduit. I'm a bit uncertain about where I can get an optimal ground connection from, although I see a few possibilities (also refer to pictures below):

1. A copper wire (I think; it's covered in stupid house paint too) with green plastic shielding/insulation that appears to come out of the ground and is not connected to anything on the end I can see. It looks like this could be it; since I don't want to use an exterior coax splitter, should I instead purchase and install a coax ground block between the splice point and attach the green wire to it? Can I verify that the green wire is grounded by touching an ohmmeter to it and to, say, my electrical mains conduit or what I think may be the ground rod?

2. A twisted steel cable of the type I've often seen attached to ground rods with a clamp/electrode. It comes from the ground near the green wire and immediately disappears up under the siding. I suspect this may run to the breaker box in the garage or something.

3. A metal rod (possibly zinc or steel, although it looks a bit rusted on the very top) protruding just a couple inches from the ground, with no electrode/clamp attached. Could this be the ground rod, with everything connecting underground? It does look like the green wire and twisted steel cable come out of the ground just a few inches away, on the house side of the rod.

4. The natural gas meter conduit on the opposite end of the wall has some wires attached to it that come out of the ground right next to it.

Here are some more pictures in case they help:
- Closeup of possible ground connections: »docs.google.com/open?id= ··· obWZuUGM - note the twisted steel cable near the top left, green wire near top middle, and rod at lower left
- Wider shot of electrical/cable/telephone area: »docs.google.com/open?id= ··· ETGg4eVk - large conduit on left is electrical mains (with meter at the top), small conduit next to it goes to an RV power outlet, and rightmost conduit goes to telephone connection box. Cable comes from underground near the telephone conduit, and splice box is lashed to the same conduit.
- Even wider shot of the above, showing the electrical meter: »docs.google.com/open?id= ··· UZ1REVTQ
- Even wider shot of west side of house, with gas meter on right and electrical/cable/telephone on left: »docs.google.com/open?id= ··· YZFpvTnM

retiredqwest
join:2005-04-01
Spokane, WA

retiredqwest

Member

quote:
1. A copper wire (I think; it's covered in stupid house paint too) with green plastic shielding/insulation that appears to come out of the ground and is not connected to anything on the end I can see. It looks like this could be it; since I don't want to use an exterior coax splitter, should I instead purchase and install a coax ground block between the splice point and attach the green wire to it? Can I verify that the green wire is grounded by touching an ohmmeter to it and to, say, my electrical mains conduit or what I think may be the ground rod?

That is probably the ground wire that may have been attached to the coax ground block. Telco and CATV use a #6 wire w/green insulation for that purpose.

Using a Multimeter, set it on AC Voltage FIRST and test the wire. Then test it using the ohms scale.
quote:
2. A twisted steel cable of the type I've often seen attached to ground rods with a clamp/electrode. It comes from the ground near the green wire and immediately disappears up under the siding. I suspect this may run to the breaker box in the garage or something.

That is probably the power ground to the breaker panel.
quote:
3. A metal rod (possibly zinc or steel, although it looks a bit rusted on the very top) protruding just a couple inches from the ground, with no electrode/clamp attached. Could this be the ground rod, with everything connecting underground? It does look like the green wire and twisted steel cable come out of the ground just a few inches away, on the house side of the rod.
That is a 6-8' ground rod, if you dig down there should be 3 connections attached to it. CATV, Power, and Telco attach to it to make a 'common' ground.
quote:
4. The natural gas meter conduit on the opposite end of the wall has some wires attached to it that come out of the ground right next to it.

Those are used to attach a cable locator, since the pipe below the ground is plastic to the street.

IMO, you should make Comcast come out and fix that mess. You really shouldn't have to fix things and legally they are responsible to make sure that the coax has adequate grounding at your premises.

You may also want to consider rewiring the entire house. Ya, I saw you mentioned a crawl space..... If you wire the house and do what we call a 'home run' with each outlet you could probably eliminate most of the splitters you have now and maybe even the AMP. It all depends if you have the time and how long you think you are going to stay in that house if you want to make the effort.

HunterZ
join:2003-07-16
Kent, WA

HunterZ

Member

Thanks, I'll contact Comcast about having a grounding block installed on the tap.

I'm not a huge fan of crawlspaces (especially ones that previously had mice in them), but I think I should really run a new 25-30 foot cable from the outside of the house down into the crawlspace and over to the family room. Are there any good options for having someone else do this without paying an arm and a leg?

I also really don't want to re-wire the whole house at this time; I just want to have both the TV and Internet service in the family room (I already have wifi and HomePlug AV equipment to distribute the LAN/WAN throughout the house), and we currently have no plans to use TVs anywhere else in the house.

retiredqwest
join:2005-04-01
Spokane, WA

retiredqwest

Member

I think you might be hard pressed to find someone willing to do the crawlspace thing on the cheap. Especially concerning mice and Hanta Virus.

The Comcast tech will more than likely not be interested in doing it either... but it won't hurt to ask how much to install the line.

He might be willing to provide the RG6 cable for free. So, if you get the cable placed they will come back and install the connectors for free.

Is it possible to get close enough to the family room on the outside of the house?

On Craigslist, there's some guy in Kirkland who will install coax for a $1 a foot....8)

HunterZ
join:2003-07-16
Kent, WA

1 edit

HunterZ

Member

I'm actually a bit confused about where the current line to the family room is installed; it goes into a hole in the garage wall and then disappears, but my understanding is that it's not likely that there is crawlspace under the concrete-floored 3-car garage. I think there's a vent in the foundation on that side of the house, though, so I guess there must be a space under it?

Going around the outside wouldn't work too well, but I have been thinking of an alternative: the built-in entertainment center shares a wall with the garage, so I could drill into the garage by going right through the back of the existing cable hole. I could then tack up RG6 around the garage to where the existing cable comes in. This would involve going over a door and behind the tankless water heater and furnace, but I don't think any of that would be too dicey.