: Lets talk cable modems



Dadillac
12-02-06, 08:27 AM
For the past two days I have been having an intermittent (sp) issue with my cable modem. It is a Terayon TJ 715 that is provided through Comcast. It will just lose the cable signal and I have no internet.

The cable line is on the outside of the house, goes into a four way splitter, and then the various cables run into the house (it was like this when I bought the house). I recently changed out the splitter and the cable going to my living room tv.

When I lose the cable signal, all of the tv'z in the house work fine, but the unternet doesn't work. So I am thinking that the actual cables must be fine. The cable connection on the modem is quite warm. Is it supposed to be, or is it getting too hot? I recently had a computer meltdown, and had to do a complete recovery. Could something in the computer be causing the modem to not function properly? Thanks for any info

Don

CIWS
12-02-06, 09:05 AM
The fact that you're not losing TV as well tends to discount it being related to a connector or line. However your internet connect can go on the fritz and not affect your TV signal, two seperate frequencies being transmitted in the line.

If you have other computers in the house, have you looked to see if they have also lost connectivity at the same time ?

Do all of the PCs in the house connect via an LAN cable to a router/modem or are some wireless ?

It's always possible you inet connection is simply dropping out.

Rey Rey 650
12-02-06, 09:16 AM
:topicsucks:

Rey Rey 650
12-02-06, 09:19 AM
Sorry didnt really mean to do that.....Its 6am and i'll be off in 3 more hours.....Graveyard sucks and i think im going :cookoo:

JimHare
12-02-06, 09:31 AM
Dad, first thing I'd do is take the modem back to the local Comcast office and trade it for another - this will tell you if the problem is cable modem related or not. Then we can go from there....

Just as an aside, thought you DSL users might like to see this - just did a speed test on my Comcast line:

Elvis
12-02-06, 09:36 AM
My parents had to have some kind of a signal booster just for their cable modem.

Their television signals were fine, but there's some box plugged into the line and the wall right by the modem.

Mine's on a direct link, it's the only cable service I have, so the signal isn't depleted by anything.

xxpinballxx
12-02-06, 09:44 AM
My modem does the same thing from time to time. It seems to be in worse weather...windy...when it happens. I have to go up to the modem unplug the power supply the replug it and refresh connections. I thought it was something with my router at first but because I have the two power pugs on the same power strip so I just clicked them both off and back on. Then one day tries just doing the router and it didn't work. really pisses me off cause its a whole process for me to get comfortable with my laptop in my lap in my chair downstairs to only find out i have to run upstairs and turn the damn thing on and off.

CIWS
12-02-06, 09:48 AM
Just as an aside, thought you DSL users might like to see this - just did a speed test on my Comcast line:


Dam Jim you better call them up and tell them that upload speed sucks :D






;)

codewize
12-02-06, 09:50 AM
Fact: Most cable companies won't hook a modem up to a 4 way slitter for just that reason. The drop signal is usually around 20db Ever split drops that signal 7 - 10 db. The threshold for a cable modem is usually 5 db. With a 4 way splitter it should even work. I have a feeling it's operating right on the signal threshold

The proper way to connect a cable modem is directly to the first 2-way splitter off the drop. Then you take the other side of that and split it for television. You'll be much happier.

I designed and built our local cable plant for the very first cable modem roll out in the area. Trust me on this info.

CIWS
12-02-06, 10:00 AM
The split info is correct, each split will typically drop a signal at least 3db, but it depends on the splitter and how much signal loss actually occurs. However if the incoming signal is of sufficent strength, even with the split loss it can still be strong enough. Every situation is different.

xxpinballxx
12-02-06, 10:07 AM
well code described mine exactly.....split outside....
one goes to my modem the other into the basement and split up to four tv's inside.

dp102288
12-02-06, 10:28 AM
My cable is two way split (one direct for the modem) and then split like hell for the house.

Jim...nice dl speed but the up really sucks.

Your in NJ and can get Comcast...how much do you pay a month for that? I pay $50 for 15/2 (really 12/1.5)

Dadillac
12-02-06, 11:20 AM
I went to the Comcast service center to swap the modem. Got a different modem (RCA now) and it seems fine. Just before I left I tried replying to this thread, and I lost my connection. That was it for me. It seems like the new modem is running cooler also. Strange

Don

railven
12-02-06, 11:27 AM
When you said you changed the splitter the first thoughts I got Code already covered.

I usually single out internal factors before swapping hardware, I'm stubborn haha.

If the new modem is doing it for you all is good.

JimHare
12-02-06, 12:59 PM
My cable is two way split (one direct for the modem) and then split like hell for the house.

Jim...nice dl speed but the up really sucks.

Your in NJ and can get Comcast...how much do you pay a month for that? I pay $50 for 15/2 (really 12/1.5)


I think that Comcast only advertises a max UPLOAD of 384K, so I'm not all that concerned. Only makes a big difference when I'm uploading to the Hare-Net web site anyway.

I pay $42.95 per month for the CHSI, I think. Have a Netgear wireless router for the two connections upstairs, and my 'puter is cabled directly to the router.

Have the RCA DCM425C unit (I hesitate to call it a 'modem', since that's not really what it does (modulate/demodulate) like the old analog phone things do.

Dadillac
12-02-06, 02:37 PM
I think that Comcast only advertises a max UPLOAD of 384K, so I'm not all that concerned. Only makes a big difference when I'm uploading to the Hare-Net web site anyway.

I pay $42.95 per month for the CHSI, I think. Have a Netgear wireless router for the two connections upstairs, and my 'puter is cabled directly to the router.

Have the RCA DCM425C unit (I hesitate to call it a 'modem', since that's not really what it does (modulate/demodulate) like the old analog phone things do.

I now have the RCA DCM425. First thing I am noticing is that the cable wire and connector are cool to the touch. I assume that the Terayon was overheating. I have had a rough week for computers and hardware.

Don

railven
12-02-06, 03:09 PM
I wrote a response about electromagnetic fields and my net crapped out.

Hmmm I'm not happy with this at all and I just noticed some suspicious programs running in the background.

Odd thing is no one...sigh except my girlfriend...has used my computer. I hope she didn't screw mine up its acting like hers was back in the old house, not loading pages and losing connection.

Time to investigate.

codewize
12-02-06, 03:18 PM
That is correct. Everything varies but as a general rule of thumb you want the modem off the first 2-way split. The quality of the splitter does play a big part in the signal degradation.

The threshold of each brand of modem will vary also but they are pretty close actually.

Usually if the problem isn't signal strength it's with the return path. Make the cable company check for water in the tap (thing on the pole). and check for a good ground at the ground block



The split info is correct, each split will typically drop a signal at least 3db, but it depends on the splitter and how much signal loss actually occurs. However if the incoming signal is of sufficient strength, even with the split loss it can still be strong enough. Every situation is different.

railven
12-02-06, 03:24 PM
That is correct. Everything varies but as a general rule of thumb you want the modem off the first 2-way split. The quality of the splitter does play a big part in the signal degradation.

The threshold of each brand of modem will vary also but they are pretty close actually.

Usually if the problem isn't signal strength it's with the return path. Make the cable company check for water in the tap (thing on the pole). and check for a good ground at the ground block

You'll also need a splitter that can handle the bandwidth the cable is running. If it cost two dollars or less chances are it won't support it.

Also check your cable lines themselves and use at least RG6.

I've also read that make sure all your coxial connections are secure and tight as you can leak signal through a loose connection.

dp102288
12-02-06, 10:55 PM
I pay $42.95 per month for the CHSI

Man I would pay an easy $60 for those speeds...I never upload anything anyways...always download sthings i don't need.

codewize
12-03-06, 12:42 AM
IP relies on 2 way communication to function. If the upstream is broken or faulting your whole connection will go to crap in a hurry.


Man I would pay an easy $60 for those speeds...I never upload anything anyways...always download sthings i don't need.

JimHare
12-03-06, 08:18 AM
Man I would pay an easy $60 for those speeds...I never upload anything anyways...always download sthings i don't need.

I think one of my advantages is that my local area is relatively sparsely populated, so I'm not competing with a lot of other cable modems. This part of New Jersey is far different than the northern areas where you are. From what I understand, the more internet users on a particular branch of cable, the less bandwidth each can expect to get from a fixed signal. I'm in the Comcast-Vineland pot and the nearest area with any real density is probably 20-25 miles north of me in the Camden/Cherry Hill area, which is in a different Comcast territory.

This may, however, be the only benefit to Salem County.. lol

dp102288
12-03-06, 09:51 AM
IP relies on 2 way communication to function. If the upstream is broken or faulting your whole connection will go to crap in a hurry.



True, but for simple page requests 384 is probably more than enough (well it was when i did have DSL)

However, when the up does get too low, I know the internet can break on your end.

dp102288
12-03-06, 09:53 AM
I think one of my advantages is that my local area is relatively sparsely populated, so I'm not competing with a lot of other cable modems. This part of New Jersey is far different than the northern areas where you are. From what I understand, the more internet users on a particular branch of cable, the less bandwidth each can expect to get from a fixed signal. I'm in the Comcast-Vineland pot and the nearest area with any real density is probably 20-25 miles north of me in the Camden/Cherry Hill area, which is in a different Comcast territory.

This may, however, be the only benefit to Salem County.. lol

It is true...the more users on a single main line the more people suffer. I am kinda lucky, in my area there are a lot of houses. now either not a lot are on cable, or they well equipped the area. I don't care...I love it!

Northern area...more like centeral! :p North NJ is too close to NYC for me (I don't like NYC).

codewize
12-03-06, 11:01 AM
Correct. Cable plants are broken up into areas or 'nodes'. This is done for several reasons. One is to combat the plant form becoming saturated and to be able to manage bandwidth.

The problem is during the design of most cable plants the Internet wasn't what is is today. As a result cable model plants are becoming way over utilized by customers. The result of course is everyone's connection is slower.

I know locally they just split 2 nodes into 4 because it was so bad. Providing residential bandwidth never makes money. It's a loosing battle 100% of the time.

Verizon has the right idea with all fiber network. It's flexible and scalable

JimHare
12-04-06, 07:55 AM
Northern area...more like centeral! :p North NJ is too close to NYC for me (I don't like NYC).


I suppose you're correct - I tend to think of anything north of the AC Expressway as "North Jersey"...:eek:

To give you an idea, within a FIVE-MILE radius of my house, there are exactly four stoplights...

ewill3rd
12-04-06, 08:31 AM
The cable split should be done with the proper splitter with one leg going to your TV and one to the modem.
If you have more than about 3 TVs you should have a signal booster put on that segment of the cable AFTER your first splitter.
Do you have a home network?
I would suspect the router for an intermittent outage before I'd suspect the modem.
Make sure all your equipment is powered through a surge protector, router, signal booster, computers... all of it.
If you suspect the modem, comcast should supply you with a new one or send out a tech to check it.

dp102288
12-04-06, 09:37 AM
To give you an idea, within a FIVE-MILE radius of my house, there are exactly four stoplights...

That sounds like it would be too much fin for me! :stirpot:

codewize
12-04-06, 02:50 PM
For every 4 splits you should add a 10db amp

Why would you blame a router for an outage? That's something the county workers in my wife's office would say. I have routers deployed that I haven't seen in years. A router is a pretty damn reliable piece of equipment. If it's not the you should get something else.

How unreliable would the Internet be if routers randomly caused outages?


The cable split should be done with the proper splitter with one leg going to your TV and one to the modem.
If you have more than about 3 TVs you should have a signal booster put on that segment of the cable AFTER your first splitter.
Do you have a home network?
I would suspect the router for an intermittent outage before I'd suspect the modem.
Make sure all your equipment is powered through a surge protector, router, signal booster, computers... all of it.
If you suspect the modem, comcast should supply you with a new one or send out a tech to check it.

ewill3rd
12-04-06, 03:20 PM
Sorry, to clarify let me put it this way.
I had a problem with a Belkin router, that was otherwise great.
It would periodically lose connection to the internet for about 2 minute intervals. I tried all kinds of things to get rid of it and I pretty much gave up and had the same problem for about 4 years. I used the router in DSL in CA and on Cable here in VA. My wife finally complained and the more I thought about it the more I realized it was the weakest link in the chain.
I replaced it with a Linksys cisco BEFSR41 and haven't lost access to the web for a second.

What I meant to say is that personally, as a home user, not a professional, I would suspect a problem with the router before I would condemn the cable modem for that type of intermittent condition.
That doesn't mean I'd run out and buy one, just that the original poster might look into the possibility. I hold no grudge against my Belkin router but it did seem to be the source of the trouble.

dp102288
12-05-06, 10:01 AM
The first Netgear router I had wouldn't keep a connection with any Centrino laptop...mom has one. :(

Got a Linksys one...works great. And I changed the firmware!! :D

railven
12-05-06, 11:11 AM
I've gone through about six routers, first two being netgears [their earlier generation work caused me to despise them as they always costed 10-20 more then other equipment but failed to deliver a premium], Linksys, same as Netgear, and then I switched over to D-Links.

Even though the routers didn't work great I can't say I loss connection once with any of them. Usually my cable modem would reboot randomly, turned out to be a heating issue, and the last problem I had I never problem solved.

My biggest complaint with the first routers I had was their poor managment of data streaming and their lack of configurations for packets.