Cable Modem question
This is probably a dumb question, but I was sent a 25 ft coax cable to hook up my new cable modem. I needed a longer cable and went to their office but that was all they had so they gave me another 25 ft cable with a connector attached to it (not a splitter, just a round metal adapter) so I could put both cables together to make it 50 ft.
Will doing this degrade the signal at all, having 2 25ft cables connected together vs just a 50 ft cable?
Thanks,
Steve
Will doing this degrade the signal at all, having 2 25ft cables connected together vs just a 50 ft cable?
Thanks,
Steve
Comments
It is a bit like a digital satellite signal. If you can see the picture, even if the signal strength is 50 percent, you are fine.
You should be able to reach your cable modem's diagnostics page by clicking this link: http://192.168.100.1/
It should be able to tell you your SNR and power levels. Mine for example:
35 dB downstream SNR
-9 dBmV downstream power
29 dBmV upstream power
Originally posted by Eugene
You should be able to reach your cable modem's diagnostics page by clicking this link: http://192.168.100.1/
It should be able to tell you your SNR and power levels. Mine for example:
35 dB downstream SNR
-9 dBmV downstream power
29 dBmV upstream power
Dude, you just got elevated on my friendship-o-meter.
Does this also work for other internet types? (DSL, T1, etc...)
Originally posted by Ebby
www.broadbandreports.com and it's Cable FAQ.
Does this also work for other internet types? (DSL, T1, etc...)
No, it's mostly a cable modem thing and it doesn't even work on all cable modems. It also might not work if you're using a braindead router between your computer and cable modem.
In general you want:
downstream SNR >30 dB
downstream power -8 to 8 dBmV (-15 to 15 is within spec)
upstream power <50 dBmV (the lower the better)
And Eugene you mind reader, being able to test the modem was my next question. These are the results I got, what do you think?
Frequency
603000000 Hz Locked
Signal to Noise Ratio
35 dB
QAM
64
Network Access Control Object
ON
Power Level
-5 dBmV
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
Upstream
Value
Channel ID
2
Frequency
25008000 Hz Ranged
Ranging Service ID
7238
Symbol Rate
2.560 Msym/s
Power Level
58 dBmV
http://www.dslreports.com/faq/3368
Basically the modem is encountering a lot of noise on the upstream link and it has to use more power to muscle the signal through. Another issue with high power levels is that your cable modem actually runs hotter.
Do you know how your cable is set-up? Do you cable TV? How many splits do you have?
Originally posted by Eugene
The upstream power levels are very high, but if it works, it works.
http://www.dslreports.com/faq/3368
Basically the modem is encountering a lot of noise on the upstream link and it has to use more power to muscle the signal through. Another issue with high power levels is that your cable modem actually runs hotter.
Do you know how your cable is set-up? Do you cable TV? How many splits do you have?
I have a cable running from my upstairs TV to downstairs. The Cable is then split, one signal going to my cable modem and the other going into the downstairs living room TV. From that TV, theres another splitter where the cable goes into my bedroom TV. Think this may be the reason?
Should I mention the poor numbers to my cable provider?
Originally posted by steve666
I have a cable running from my upstairs TV to downstairs. The Cable is then split, one signal going to my cable modem and the other going into the downstairs living room TV. From that TV, theres another splitter where the cable goes into my bedroom TV. Think this may be the reason?
Should I mention the poor numbers to my cable provider?
What do you mean you have a cable running from your upstairs TV to downstairs? Where does the cable come in? Are all these devices in different rooms? Do these rooms has cable outlets? You need to be more descriptive of your lay-out.
Is this your set-up using 3 two-way splitters?
upstairs TV (-3.5 dB)
main cable_/
\\ cable modem (-7 dB)
\\/
\\ downstairs TV (-10.5 dB)
\\/
\\
bedroom TV (-10.5 dB)
The optimal set-up is to use one 2-way splitter and one balanced 3-way splitter like this:
cable modem (-3.5 dB)
main cable_/
\\ upstairs TV (-9.2 dB)
\\/
/\\
(-9.2 dB) TV downstairs TV (-9.2 dB)
Every 2-way splitter results in a 3.5 dB loss of signal strength, so in the first situation you've already lost 7 dB by the time you've reached the cable modem. A balanced 3-way splitter has 5.7 dB loss on each line.
My set-up uses one unbalanced 3-way splitter (just like two 2-way splits) where the main cable comes in. Two go to TVs in different rooms. One goes to a room where it is split using a special 2-way splitter that only loses 1 dB on one line and 6 dB on the other. The cable modem gets the 1 dB loss and the TV gets the 6 dB loss.
TV (-7 dB)
main cable_/
/\\ TV (-9.5 dB)
(-7 dB) TV \\/
\\
cable modem (-4.5 dB)
The numbers in parantheses equals the loss from the splitters alone.
Top Floor____
/
/
Wire coming out of wall on lower floor
Three way splitter attached to wire-coax to cable modem coming out of one end , coax to another three way splitter just before the first TV. One end going to that TVs cable box, the other end another coax cable going to another TVs cable box in my bedroom.
Basically I have no cable outlets in the house. There is a coax cable coming straight out of the wall in the top floor, then another cable coming down through the wall to the lower floor where there are the two splitters I mentioned above.
Sounds like my signal is split all over the place. I remember the Cable Guy asking if we wanted to have another Cable coming directly to the lower floor and bypass the upper floor altogether but we turned him down because we didnt want a hole drilled in the wall downstairs like there is upstairs.
Looks like Im screwed.
code: upstairs TV (-3.5 dB)
main cable_/
\\ cable modem (-7 dB)
\\/
\\ downstairs TV (-10.5 dB)
\\/
\\
bedroom TV (-10.5 dB)
I believe this is correct. The splitters have one incoming and two outgoing.
Originally posted by steve666
I believe this is correct. The splitters have one incoming and two outgoing.
Ugh...that's not a pretty sight, but if you currently don't have any problems with that set-up, then there's no reason to change it.
One thing you can do is to see if the cable company's local office and ask if they have a DC-6 or DC-9 directional coupler. It's the kind of special splitter I was talking about that has one high-loss legand one very low-loss leg. The people who work at the office might not know what you're talking about though...
Replace the very first splitter with one of these. Use the high-loss "tap" leg for the upstairs TV and the low-loss "out" leg for the cable that goes downstairs to the rest of your devices.
Originally posted by Eugene
Ugh...that's not a pretty sight, but if you currently don't have any problems with that set-up, then there's no reason to change it.
One thing you can do is to see if the cable company's local office and ask if they have a DC-6 or DC-9 directional coupler. It's the kind of special splitter I was talking about that has one high-loss legand one very low-loss leg. The people who work at the office might not know what you're talking about though...
Replace the very first splitter with one of these. Use the high-loss "tap" leg for the upstairs TV and the low-loss "out" leg for the cable that goes downstairs to the rest of your devices.
OK, I'll give it a shot, thanks for all the info.
I just checked the 2 downstairs splitters and they say (-3.5db) for each out. Is this OK?
There must be a direct cable into the lower floor because there is no splitter upstairs. The cable i thought was going through the upstairs wall to downstairs must be going outside to the main cable hookup.
The cable coming out of the downstairs wall must be going outside to another cable hookup.
I think the cable guy had said he would put another hole downstairs because i was unhappy with the reception in my downstairs bedroom and he was going to eliminate the splitter going from the downstairs living room TV to my bedroom TV.
Now that I got that straight, there are only 2 splitters. Are those (-3.5) splitters OK? I dont want to degrade my cable reception any more than it is now.
And, I guess coupling those 2 25 ft coax cables together isnt an issue?
Man, dial-up is much less of a hassle! But I am enjoying the speed boost.
Incidentally, has anyone ever tried a dial-up service like earthlink that claims web page loading 5X the speed of regular 56k dial-up? I had been considering that too before deciding on cable (I hate my cable company-greedy pigs!)
downstream power > -16 dBmV
upstream power <38 dBmV
Hmmm... That's mine. All I know is it works, and pretty well for $50 a month. It's a h3ll of a lot better than dial up.
Originally posted by steve666
Now that I got that straight, there are only 2 splitters. Are those (-3.5) splitters OK? I dont want to degrade my cable reception any more than it is now.
Like I said, if you you haven't had any actual dropped connections or loss of modem sync issues, then you don't need to change anything. The power levels and SNR could probably be improved just by moving the cables away from power strips and other power cords as well.
Don't worry about it.
Thanks for all the info guys
Originally posted by steve666
OK, I guess since its working I will leave everything alone, although I am considering that DC-9 or DC-6 splitter you mentioned thats between my living room TV and my bedroom TV because my bedroom gets worse reception and thats where my VCR is hooked up.
Thanks for all the info guys
No, don't do that. I would only put the DC-9 or DC-6 at the very first split in this case. If you use a DC-6 or DC-9 to get better reception in your bedroom, you'll get worse reception in the living room.
Originally posted by Eugene
No, don't do that. I would only put the DC-9 or DC-6 at the very first split in this case. If you use a DC-6 or DC-9 to get better reception in your bedroom, you'll get worse reception in the living room.
Would it be considerably worse? The thing is I tape off of my bedroom VCR and it is annoying when the picture looks grainy.
Originally posted by steve666
Would it be considerably worse? The thing is I tape off of my bedroom VCR and it is annoying when the picture looks grainy.
You would noticeably improve reception on all your downstairs TVs if you used a DC-6 (directional coupler) at the very first split. It shaves a couple of dB from all the devices downstairs while weakening the reception of the upstairs TV. Since the upstairs TV is only off one split, it's not so bad.
I still think you have three 2-way splitters in a chained configuration. If you have a a cable box on the side of your house, that's probably where the first splitter is located.
What I think your current set-up is:
upstairs TV (-3.5 dB)
/
main cable----------------1
\\
2--cable modem (-7 dB)
/
bedroom TV (-10.5 dB)--3
\\
downstairs TV (-10.5 dB)
(1) 2-way splitter
(2) 2-way splitter
(3) 2-way splitter
How to balance out the signal strength distribution:
upstairs TV (-6 dB)
/
main cable-------------1
\\
2--cable modem (-4.5 dB)
/
bedroom TV (-8 dB)--3
\\
downstairs TV (-8 dB)
(1) DC6 directional coupler
(2) 2-way splitter
(3) 2-way splitter