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rauljimenez

join:2006-01-09
Guaynabo, PR

In need of Attenuator?? Cable modem

Hello, A lot of people have been very valuable in this board helping me out. Can you guys help me out and see if my signal levels look ok or do I need an attenuator or a possible DC(Directional Coupler 12). Right now I got an aerial connection that drops into a DIRECTIONAL COUPLER 6DB. I got the modem attached to the tap and in the out I got the 2 tv's.

Here are my signal levels
Downstream Value
Frequency 573000000 Hz
Signal to Noise Ratio 36 dB
QAM 256
Network Access Control Object ON
Power Level 9 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 33000000 Hz
Ranging Service ID 184
Symbol Rate 2.560 Msym/s
Power Level 36 dBmV


all_in_1
Premium
join:2002-07-05
Beatrice, NE

A DC 12 will help. It will get your signals closer to the mid range of the signal spec's.


rauljimenez

join:2006-01-09
Guaynabo, PR
reply to rauljimenez

I think my upstream level is still a bit low am I right?


all_in_1
Premium
join:2002-07-05
Beatrice, NE

1 edit
reply to rauljimenez

Your upstream will go up to +42 and your downstream will fall to +3. Both are better (improved) levels.



cablegeek01

join:2003-05-13
USA
kudos:1

exactly,
0dBmV on the downstream, and 48dBmV on the upstream are your magic numbers (as well as +35 DS SNR and +27 US SNR)

The closer you can get to these numbers, the more reliable your service will be, as long as there isn't a major problem further down the cable line.


rauljimenez

join:2006-01-09
Guaynabo, PR
reply to rauljimenez

Yep then i'll definitely get a Directional Coupler DC 12 from REGAL thanks guys!!



burner50
Proud Union THUG
Premium
join:2002-06-05
Fort Worth, TX
kudos:1
reply to rauljimenez

i would use a dc 9 instead....


all_in_1
Premium
join:2002-07-05
Beatrice, NE

3 edits

If he went from a DC-6 to a DC-9, his levels would only improve by 3dB. That is, downstream would be +6 and the upstream would be +39. A DC-12 will get him closer.
Actually, if rauljimenexz wanted to get to closer to the magic levels, he should get a DC-16. That would give him a -1 down, and a +46 up. But that would be splitting hairs.



egnlsn
Premium
join:2003-09-26
Salt Lake City, UT

The upstream will be whatever the CMTS tells it to be.

It looks like the DC is connected after an amplifier, perhaps even an amp that amplifies the return path as well as the downstream. Why else would there be +25dBmV at the input of the DC-6? (9+6=15QAM. 15+10=25analog)

If that is the case, there is probably ~10-12dBmV at the input of the amp. A DC-6 prior to the amp would have his cable modem levels ~-4dBmV and upstream would probably go up to the mid-40s.
--
CIAO!



burner50
Proud Union THUG
Premium
join:2002-06-05
Fort Worth, TX
kudos:1
reply to rauljimenez

I always try and keep at least +3 to +6dB going to a modem...I know what all the "magic" numbers are, but that accounts for fluctuations in the system....

The Upstream power level is not determined by the CMTS.

The Upstream level it determined by many things, Splitters in your house, long lengths of cable, tap Plates, Line Extenders, Nodes, and padding in the Headend....


all_in_1
Premium
join:2002-07-05
Beatrice, NE

said by burner50:

The Upstream power level is not determined by the CMTS.

The Upstream level it determined by many things, Splitters in your house, long lengths of cable, tap Plates, Line Extenders, Nodes, and padding in the Headend....
While all of the external elements of the system and drop have a direct contribution to the upstream levels of a modem, It is the CMTS that dictates the upstream level of the cable modem. Most if not all CMTS's are set to see the modem a "0 DBmv" at the blades input. The modem and the CMTS talk to each other, so that the modem adjusts its output to make "0" at that input. That is why Modems Range when first put on line, to make that level, among other things.

rauljimenez

join:2006-01-09
Guaynabo, PR
reply to rauljimenez

Thanks guys, Let me give you an idea of how my catv wiring is at the house.

First the cable comes from a TAP in a pole down to my house (Aerial), as soon as the cable enters my house the DC-6 hooks that cable in the IN port, the TAP ports is connected to my cable modem and the OUT port then splits to 2 tv's... thats all there is to my house nothing else.

A bit before coming to this site, I had my levels at 14dbmV downstream and 30dbmV upstream with the cable modem hooked up at the OUT of the DC-6. Then a lot of people adviced me to hook it at the tap which I did which improved the levels to 9dbmV downstream and 36dbmV upstream. I still think this can be improved to the optimal setting by using a DC-12. Am I doing the correct thing now with all the info that i have acquired in here? chime in



Corvus
Flaming Tards Since 2003
Premium
join:2003-11-26

said by rauljimenez:

A bit before coming to this site, I had my levels at 14dbmV downstream and 30dbmV upstream with the cable modem hooked up at the OUT of the DC-6.
You're at the very end of the HFC node if you've got 30dBmV on upstream (15dB for the amplifiers + 11dB for tap at the pole or less + cable loss to your house). A tap 12dB is definitely the best solution to get close of 0dB on downstream.
--
The Republicans are the party that says government doesn't work and then gets elected and proves it.--P. J. O'Rourke

rauljimenez

join:2006-01-09
Guaynabo, PR
reply to rauljimenez

Thank you very much , I'll get the REGAL DC-12


rauljimenez

join:2006-01-09
Guaynabo, PR
reply to rauljimenez

Guys I have a problem now, after a few days of being at 9dcmV , I checked today my downstream level and they are back again at 15dbmV wtf? my upstream is still at 36 but why the hell my downstream increased so much, problem with the ISP??



egnlsn
Premium
join:2003-09-26
Salt Lake City, UT

said by rauljimenez:

Guys I have a problem now, after a few days of being at 9dcmV , I checked today my downstream level and they are back again at 15dbmV wtf? my upstream is still at 36 but why the hell my downstream increased so much, problem with the ISP??
15 + 6 = 21dBmV QAM hitting your house. 21 + 6 = 27dBmV (analog) at the groundblock. There is something going in the plant that shouldn't be. There shouldn't even be that much at the tap.

Your upstream didn't change because the CMTS tells the cable modem what power level to pump out. If it says to transmit at 36dBmV, then it transmits at 36dBmV, pretty much regardless of what happens in the system to cause input levels to jump around.

Time to call the cable company.
--
CIAO!

rauljimenez

join:2006-01-09
Guaynabo, PR
reply to rauljimenez

Thanks guys, I called my Cable end and they are going to send a tech here, now the weird thing is right now I have 17dbmV on the downstream power level and I'm not disconnected from the ISP, can a cable modem handle such high speed?? My connection has not dropped one bit, thanks.



egnlsn
Premium
join:2003-09-26
Salt Lake City, UT

said by rauljimenez:

Thanks guys, I called my Cable end and they are going to send a tech here, now the weird thing is right now I have 17dbmV on the downstream power level and I'm not disconnected from the ISP, can a cable modem handle such high speed?? My connection has not dropped one bit, thanks.
-15 to +15dBmV are the minimum/maximum levels set by CableLabs for cable modems to be operational. It is not uncommon for cable modems to work a couple of dB above or below those numbers.
--
CIAO!


Corvus
Flaming Tards Since 2003
Premium
join:2003-11-26

I've saw cable modems at -20dBmV and +20dBmv, but you can't avoid uncorrected frames with these levels.


TMac4

join:2005-11-14
Brazil
reply to rauljimenez

Before
Download power level 0
Upstream power level 51

Now
Download power level +5
Upstream power level 47

Which is better?



egnlsn
Premium
join:2003-09-26
Salt Lake City, UT

said by TMac4:

Before
Download power level 0
Upstream power level 51

Now
Download power level +5
Upstream power level 47

Which is better?
Personally, I would prefer 0/51. Not because of the 0dBmV downstream, but because of the 51dBmV upstream. The modem is shouting a little bit louder. Other noise a little less likely to be heard.
--
CIAO!


DannyZ
Gentoo Fanboy
Premium
join:2003-01-29
Erie, PA

I would take the second for sure. 51 is closer to borderline than +5 is.

You want your upstream signal as low as possible. The higher it is means the more noise is on the line, so the modem has to 'shout' louder for the cmts to hear it.


rauljimenez

join:2006-01-09
Guaynabo, PR
reply to rauljimenez

Finally my cable tech came in here and checked the line with his tool, he decided to add another DC COUPLER to the cable entering my cable modem. Here are my latest numbers

Downstream Value
Frequency 573000000 Hz
Signal to Noise Ratio 37 dB
QAM 256
Network Access Control Object ON
Power Level 7 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 33000000 Hz
Ranging Service ID 184
Symbol Rate 2.560 Msym/s
Power Level 46 dBmV

Those numbers are with 2 DC COUPLERS, one on top of the house that is a REGAL DC 9 at the tap and one DC-6 near the cable modem entry. Let me know how this looks now.



egnlsn
Premium
join:2003-09-26
Salt Lake City, UT

said by rauljimenez:

Let me know how this looks now.
Very Good!
--
CIAO!