 trparky
Premium Member
join:2000-05-24
Cleveland, OH |
to SanAntonioTx
Re: Timewarner doesn't care about me UPDATE FIXED ITWhat is funny is that my upstream power value is 51.2 dBmV in Cleveland, OH and my connection is rock solid stable.
I've been told that the maximum upstream power value depends upon the plant. |
actions · 2012-Jun-12 11:08 pm · (locked) |
 CptGeminiInside your computer
Premium Member
join:2004-11-29
Corpus Christi, TX |
said by trparky:What is funny is that my upstream power value is 51.2 dBmV in Cleveland, OH and my connection is rock solid stable.
I've been told that the maximum upstream power value depends upon the plant.
I've also been told that at least from what I can remember vaguely is that D3 services are less tolerable to signal issues. When you arent bonding channels its a bit more tolerable. I have seen my US signal go to 56 before with no issues, been told the limit was 58. |
actions · 2012-Jun-13 8:00 am · (locked) |
trparky
Premium Member
join:2000-05-24
Cleveland, OH  ·AT&T U-Verse
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trparky
Premium Member
2012-Jun-13 10:13 am
said by CptGemini:I've also been told that at least from what I can remember vaguely is that D3 services are less tolerable to signal issues. When you arent bonding channels its a bit more tolerable. I have seen my US signal go to 56 before with no issues, been told the limit was 58. Then if that's the case, TWC will have to do some work on their plant in my area to have upstream bonding work. Why I say that is because I can see my cable node, I know where it is. I've traced the cable from the node to the tap that I'm connected to and it's a very short distance. Probably less than 1000 feet. Still I have an upstream power value of 51.2 dBmV. |
actions · 2012-Jun-13 10:13 am · (locked) |
 Jabbu
Premium Member
join:2002-03-06 |
Jabbu
Premium Member
2012-Jun-13 6:20 pm
I've seen modems with -20RX/28SNR/60TX and the person wasn't complaining about anything, lol.
You can have the node in your backyard, doesn't mean your upstream is going to be lower then a house down your block.
Since d3 allows QPSK and 8-128QAM your upstream max varies from about 58 with qpsk to 54 with qam64. |
actions · 2012-Jun-13 6:20 pm · (locked) |
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news to trparky
Anon
2012-Jun-13 10:22 pm
to trparky
said by trparky:Then if that's the case, TWC will have to do some work on their plant in my area to have upstream bonding work.
Why I say that is because I can see my cable node, I know where it is. I've traced the cable from the node to the tap that I'm connected to and it's a very short distance. Probably less than 1000 feet. Still I have an upstream power value of 51.2 dBmV.
It's normal to have higher upstream power near the node or distribution amplifier, cause the first taps of a cable line are high value taps. It's the way a cable plant is designed. Node or distribution amplifier = high value taps = high upstream (high value tap) and = high donwstream power (less cable loss cause you are near the amplifier). End of line = low value tap = low upstream power = low downstream power (more cable loss). 51 dBmV upstream power near a node or distribution amplifier is ok, but if you have only 40, that's means there's something wrong (return level too high at the node or amplifier). 51 dBmV on a end of line isn't ok, there's something wrong... |
actions · 2012-Jun-13 10:22 pm · (locked) |
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said by news :It's normal to have higher upstream power near the node or distribution amplifier, cause the first taps of a cable line are high value taps. It's the way a cable plant is designed. Node or distribution amplifier = high value taps = high upstream (high value tap) and = high donwstream power (less cable loss cause you are near the amplifier). End of line = low value tap = low upstream power = low downstream power (more cable loss).
51 dBmV upstream power near a node or distribution amplifier is ok, but if you have only 40, that's means there's something wrong (return level too high at the node or amplifier). 51 dBmV on a end of line isn't ok, there's something wrong...
I never thought about it that way but it makes perfect sense... you must work for the industry  The signal level immediately from the node is always high so the node will be a able to feed everyone to the end of the trunk. So to achieve the 'target' level for the first customer in the line (people closer to the node) a high level attenuation tap should be used but this attenuation is not unidirectional (upstream and downstream) it affects both signals the same way so the modem to compensate for the added attenuation it has to increase its power output (upstream). This is not a sign of a problem just the specific characteristics of being first in line, conversely the last customer in the trunk will have a greatly diminished signal to play with so a very low attenuation tap will be required but since he is already at the end of the trunk the modem will have to use more power to reach the node. Got it right? EDIT: What would happen if another amplifier is needed/added to feed another trunk? Will the last customer of the first trunk cause problems on the second amplifier? |
actions · 2012-Jun-13 10:49 pm · (locked) |
 swintec
Premium Member
join:2003-12-19
Alfred, ME |
swintec
Premium Member
2012-Jun-13 11:00 pm
I am the very last tap on this branch and my upstream power level is 32 dBmV. No problems here. |
actions · 2012-Jun-13 11:00 pm · (locked) |
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said by swintec:I am the very last tap on this branch and my upstream power level is 32 dBmV. No problems here.
Here too last home at the end of the street... sounds like one of those horror movies My output power is 40dBmV, never had a problem. |
actions · 2012-Jun-13 11:05 pm · (locked) |
 djrobx
Premium Member
join:2000-05-31
Reno, NV |
to etaadmin
The signal level immediately from the node is always high so the node will be a able to feed everyone to the end of the trunk. So to achieve the 'target' level for the first customer in the line (people closer to the node) a high level attenuation tap should be used but this attenuation is not unidirectional (upstream and downstream) it affects both signals the same way so the modem to compensate for the added attenuation it has to increase its power output (upstream). I had to think about this one. At first I thought attenuation being equal it wouldn't matter. Either you have attenuation from cable length, or you have artificial attenuation added from a high value tap. Then I realized that cable-length attenuation impacts higher frequencies (where the downstreams are) more than low frequencies (where the upstreams are). » www.w4rp.com/ref/coax.htmlThat means if attenuation is added to each tap that "targets", say, 0db at 500mhz, the upstream will skew stronger (lower modem output levels needed) as you go further away from the amp/node. |
actions · 2012-Jun-14 9:13 pm · (locked) |
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said by djrobx:The signal level immediately from the node is always high so the node will be a able to feed everyone to the end of the trunk. So to achieve the 'target' level for the first customer in the line (people closer to the node) a high level attenuation tap should be used but this attenuation is not unidirectional (upstream and downstream) it affects both signals the same way so the modem to compensate for the added attenuation it has to increase its power output (upstream). I had to think about this one. At first I thought attenuation being equal it wouldn't matter. Either you have attenuation from cable length, or you have artificial attenuation added from a high value tap. Then I realized that cable-length attenuation impacts higher frequencies (where the downstreams are) more than low frequencies (where the upstreams are). » www.w4rp.com/ref/coax.htmlThat means if attenuation is added to each tap that "targets", say, 0db at 500mhz, the upstream will skew stronger (lower modem output levels needed) as you go further away from the amp/node. I had to think about this one too  But there is another variable that we havent taken into consideration and that is the variable gain in the receiver (downstream) This number can take any value (gain) between -15 to +15 dBmV. I don't work in the cable industry so I don't know the details but from my experience I would extrapolate this sub-system as some sort of AGC (automatic gain control) ... well sort of. The optimum value for the 'operating level range' as some motorola documents call it is 0dBmV, this means (to me) that the modem can compensate better in case the signal is too strong or too weak. The 'operating level range' can fine tune the receiver's gain in case the tap value is not an exact match. I'm sure taps come in standard values » www.taiwantrade.com.tw/t ··· S/198003quote:
Tap values available:11dB to 35dB in 3dB steps
So if a cable guy needed a 12.5db tap he would have to choose a 11db or a 14db tap. Unmatched taps could influence upstream power output too. Another thing, the cable types used in comercial and HAM radio like in Richard's site (the link that you posted) are not the same used by CATV. I don't know the specifics or the type of cable but from what I've seen it looks like a ~1 inch in diameter hardline type of cable with a thick ~1/8 in. aluminum jacket. » www.therfc.com/hardline.htm I'm sure that this type of cable has a much better RF characteristics and lower attenuation than those used in HAM radio. |
actions · 2012-Jun-14 11:31 pm · (locked) |
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But there is another variable that we havent taken into consideration and that is the variable gain in the receiver (downstream) This number can take any value (gain) between -15 to +15 dBmV. I don't work in the cable industry so I don't know the details but from my experience I would extrapolate this sub-system as some sort of AGC (automatic gain control) ... well sort of.