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Is my cable modem signal strength too low?

post #1 of 9
Thread Starter 
Hello All

I recently have been having some issues where my Optimum Online internet connection keeps locking up and when it does it really bad, I have to unplug my modem and let it sit for a bit, then plug it back in.

Then upon restart, its fine. (IE, I never have had to do it twice)

Also I have been noticing for quite some time now on my TV's (to which is has been getting worse) I get either these partial area pixel types distortions and freezes, and or sometimes a full screen lock up on the pictures that sometimes will last a good 3-4 seconds, then it jumps back in to where it is supposed to be. And I get this from all of my sets.

To mention it, I have two older CRT TV's and one flat screen and all on various runs from the main distribution box and for all of these, they all do it and to the same amount.

Anyway, I should also mention that for the main line running into the main distribution box I first have a signal booster before it goes into that and as well, the main distribution box has about 8 output plugs to it.

But just also to mention that all of that equipment, while I can't remember the names of them off the top of my head, it is all professional grade equipment that I got from my wholesale electrical supply house and that none of it is any radio shack or monster cable or stuff like that.

Also I did all the connections and runs to everything using high grade cable from the same supply house as well as those high grade compression type fittings using the proper strippers and crimped tools to do all the work.

So when I had done all of that about 8 years ago, it all worked great and has been fine ever since.

Now I did ask one of my neighbors who understands this stuff a bit if they were having the same issues and he said that he didn't notice anything other then his boxes seem to be self rebooting a lot lately.

Anyway, I finally got around today to checking the http thing to my Motorola cable modem, which btw is the last thing on the run after all the splits to the boxes and that is giving me a reading of "3 dBmV" for my downstream power level.

Now I remember years ago when I still had a bad installation, a service tech showed me this page an how much it was improved by the installation of good splitters so I do understand the concept to that here.

So I remember checking that awhile back after I did my complete re-installation and with the booster, I thought it was much higher then 3, but its hard for me to remember. But I thought it was more like 5 or 7.

At any rate, I just thought I would ask if anyone could tell me if 3 is a good number or if it is low.

Basically right now I'm wondering if my booster, although that is looks fine, has seen its days or not as while I did a good job of installing it, it has been up in a rather hot during the summer attic for about 8 yeas now, so I just don't know what its life expectancy could be for that.

So I was planning to get to taking that out of the circuit and see what I got to test things further if this keeps happening, but in the mean time I thought I would post this here to get any more info from all that I described as that might help.

Btw, if any model numbers for anything I mention are needed, please ask for what is needed and I will get them.

Thanks for any help
post #2 of 9
I will try to answer as best as I can.

First, a dB reading of 3 is fine for cable modems on DOCSIS 2.0. My NCTI cert test labels a value of -13dB to + 10dB as 'acceptable' limits, however a reading of '0' is optimum.

If Im reading correctly,you say that the modem is the 'last' device on the distribution? In actuality it should be the first. When working for Brighthouse here we always used a DC-6(or DC-12/16/18) right after the GB(ground block).A DC is direct coupler/tap.the 'pass thru' dB loss is always -1dB and the tap varies from -6 to -18(hence DC-6/12 etc)

From time to time I have put the Cable Modem directly on a splitter(2 way or 4 way) depending on the dB I was trying to achieve at the modem.Take into account that you lose roughly 2dB per 100' depending on COAX used.

Hopefully you have only 1 splitter and not several which would be 'cascading' splitters and of course you lose more dB with each splitter you also lose return and add SNR,both of which would affect the modem operation.

I will post pics of my install. Cable companies give you a 'free' install but I never trust them as their training is 1 week classroom and 1 week ride along before they are thrown out into the field.Needless to say Ive always done my own installs and had them just drop off the equipment,I even called and had equipment authorized myself(helps to have been a former employee and know all the company numbers)
post #3 of 9
the first pic shows the ground block and the DC-6(outside at power meter)

the second pic shows the DC-6 value.(the black rg6 on bottom goes directly to my 'first' modem.the white rg6 is my HR to structured enclosure in laundry room)

the third pic is panel. my thumb is on HR and finger on the HR for the 'second' modem.This is actually a powered amp with 4 outputs as well as a passive output that the 'second' modem is connected to.

off the DC-6 to the modem I have a dB of +2.3 which is higher than I want but well within limits.The second modem has a value of -.05( -1dB from DC-6 and -1dB from passive output at amp)

I looked over your post again and missed the part of neighbor having issues.If a neighborhood has issues it comes down to a Node or feeder/trunk lines or headend issue.
Two neighbors and no more sounds like a Tap issue(the tap inside the green box/pedestal in your or neighbors yard)

I will add that the cable god has a sense of humor. I have seen issues of a loose fitting,long stinger,loose ground and many others that have caused issues. In just under 10yrs of experience in the Cable MSO field there was only one issue that I couldnt troubleshoot and fix and it still haunts me today.
A customers modem would reboot everyday at precisely 1:02PM.Swapping the modem didnt help,replacing the modem line didnt work,replacing the drop passives didnt work,replacing the underground service drop didnt work and finally I even replaced the tap at the ped,still same issue.blows my mind even today.
post #4 of 9
pics didnt attach so here they are
post #5 of 9
Thread Starter 
Hello cabledawg and thansk for the reply

I have to say that some of this is a bit over my head though. Just for the record, I am a HVAC contractor that went through all my state licensings many years ago and have run my own business now for 15. And mostly I work on the computer rm A/C stuff too. So I know some tech stuff but most of the technical stuff of that is not known to me.

But hey, you can't know everything right.

But just to ask, I think when you say Rg6 you are referring to your cable type, but what is the DC-6. I gather from reading your post you are talking about your splitter, so is that just the generic name for those like Rg6 is for the wire?

Anyway, for what I can discuss, yeah my cable modem is the last on the run and goes through 2 splitters before it gets its feed and the total run has to be about 100ft from that main distribution of 8 I spoke of. And basically this would be length to describe but this pretty much is the way it has to be.

So far it has been fine this way ever since the redo I did, and actually was even fine before that, after the Tech guy swapped the splitters.

But its good to hear that this dB is OK.

The next bit of news is that after I made this post I sent my neighbor a e-mail with a link to that test url and he wrote me back saying he had the same pixel issues happen to him last night too.

For the run in the neighborhood he is one house down and across the street but his tap is closer then mine to the feed and I know that for sure as we are on a dead end road that goes into the woods.

At any rate, if there is any more you can provide that would be great. But at least I'm thinking now that my booster is OK, but if it stays the same, I may still check it.

Thanks again.
post #6 of 9
you should never run a modem/emta off an amp,you should also have the modem before the other splitter. It will work but over time you will be feeding to much signal into modem which can cause an issue

Im not familiar with your provider but they should come out and fix the situation.Im unsure of there standards but almost all require the modem to be split off prior to other tv's and receivers.If this is the same modem for 8 years I would suggest that you schedule a service call for internet issue and request a dedicated line( from first DC/splitter directly to modem) as well as swapping the modem for giggles. Most providers provide free service calls as long as it isnt a customer caused issue which yours wouldnt be.

DC-6 is the type(mine is Altronix) it stands for Direct Coupling with -6dB loss on tap output.

If the provider gives you crap or wants to charge I suggest you run your own RG6 from prior to existing amp to the modem location. you can purchase DC's locally or online for around $4,you could also use a 2way splitter as long as its rated for 1ghz(2ghz would be better for future).Install the DC or 2way prior to the amp(booster). I hope the second splitter you mention is after the existing amp. are you using all 8 outputs on amp? how many outlets are you using in the house?(modem+tv's= ?)

post #7 of 9
does your amp look like any of these?
post #8 of 9
Thread Starter 
Originally Posted by cabledawg View Post

does your amp look like any of these?

Thanks for the info cabledawg.

As you are thankfully interested, please give me a few days and I will go through everything and give you as much info as I can.

You will have to forgive me that I don't know off the top of my head all the info I had cold when I did all this so long ago but as that was the last time I had to think about it has been quite out of site out of mind for some time now and it is all installed up in the attic and the left over wire is in the barn and packed away and all stuff like that, so its going to take me a bit to gather everything.

But just to mention it, neither of those units you have pictured look like my amp. Nore does it look like the one you have in your house.

Actually the amp is a separate part and the one thing that always struck me as unique about it is that its separate plug in 120v transformer that it came with has a cable lead tap instead of a power connection, and so the amp itself had the same, to which I had to fab up a power lead for that just like I did all the other lines and use the same cable and compression fittings as I used for the runs.

Also I'm 99% sure the cable line I used was of at least the Belden brand and I think it was double shielded as I had to be sure I got the right compression crimp fittings for it as they were not the same as typical cable lines.

But anyway give me a few days and I'll go over it all and give you a better report with all the numbers and info I can and also about how this all came to be.

It may be a little long and I'll do my best to keep it short but I figure I might as well get this all for myself anyways for any future needs.

Thanks again for the help so far cabledawg
post #9 of 9
Those amps are just common ones used in the cable field.They are also powered like you describe. They are powered by a wall transformer that uses the coax for transmission. you have the option to run a dedicated line for power or use optional 'power inserter'(Tap) with allows for 'remote' powering. I always power dedicated as I mount the amp in a structured enclosure and there is always a power outlet nearby, six in one hand half a dozen in the other.

The gray amp pictured is an older model and have been known to fritz out after years.If your amp has been up in the attic for a number of years its possible that it is going out which would explain your TV issue as well as modem issue if it is connected to the amp.

The wiring layout is what info would help,even if you just scan a hand drawn layout and upload would help.
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