Can someone tell me what the Download power levels are

deuse · 04-11-2009, 08:28

Hi all.

Can some one here please tell me what the Download Power levels shoud be for a 50Mb connection
I.E min and the max they should be.

The reason being I had problems and 2 tech guys said that my DL power levels was to high at 3.4

This is what they are at the moment

Frequency 299000000 307000000 315000000 323000000
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 5 6 7 8
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 I=12
J=17
Power Level
(dBmV) 4.14 5.30 3.90 4.20

RxMER
(dB) 36.84 36.84 36.84 37.09
Correctable
Codewords 18 2 9 2
Uncorrectable
Codewords 288 263 266 251

When my DL power levels are low i.e 1.6-2.0 I don't have any problems.

So if someone in the know could tell me please.

thanks for your time

Sephiroth · 04-11-2009, 08:53

You've answered your own question!

The downstream power level should be as close to zero as possible so that under varying line conditions there is margin to fluctuate either side. So if you're seeing constatnt power levels above 3 dBmv, then something's amiss. How amiss? Have alook that this thread:

http://www.cableforum.co.uk/board/12...al-levels.html

It's difficult to tell from your stat whether there's a modem fault or whether there's an instability in the network somewhere. It might be that your coax needs screwing in tightly.

Does that help? Prolly not because your power levels are not outrageous.

Other brainios could venture an opinion too.

deuse · 04-11-2009, 09:03

Thank you Sephiroth

I posted on the newsgroup and they said the levels are fine!
They do go upto 5+ sometimes but come down during the day.

I am going to change the cable now and see if that makes it better and read that thread you posted.

Sephiroth · 04-11-2009, 09:37

Quote:

Originally Posted by deuse

Thank you Sephiroth

I posted on the newsgroup and they said the levels are fine!
They do go upto 5+ sometimes but come down during the day.

I am going to change the cable now and see if that makes it better and read that thread you posted.

Well yes - the levels are within published tolerances. But IMO they should not be consistently towards one end of the tolerance range. If you see the levels fluctuating to something closer to 0 then something's happening when they stretch out to 5 dBmv, especially if you see corresponding speed differences.

So we need to find out what's happening.

So now tell us what speeds you're getting under the conditions. Use a download rather than that wretched speedtest.net.

deuse · 04-11-2009, 09:50

Well if I use http://gamefiles.virginmedia.com/blueyondergames/demos/
I can get 5Mb when my Power levels are low if they are about 3.0-4.0 I get about 4Mb

When I first had 50Mb installed my levels was 0.9-0.0 and all was great

but after a month the levels started to get higher and the techs that came out said they knew very little about 50Mb
and just replaced modem and went. Now my Levels are down to 2.4-2.95 so it's getting better.

I would just like to know why the levels start off at 5.0 then during the day come down to 1.5 and working.

deuse · 05-11-2009, 10:15

I just had this fron VM tech

" Ideally, for the
downstream modulation that your modem is running on (QAM256) we would like
to see the levels between +6 to -3dBmV but these levels are a guide and we
can see devices working fine outside these levels."

Ok well how come 3 VM tech guys say that it should be 3+\- ?
and when I post on the newsgroup that my levels was 4.0+ they said "We will have to send a Guy round to fix it" ?
talk about moving the gaol posts.

Ignitionnet · 05-11-2009, 10:18

+/-3 is ideal sure, but it's certainly a very long way from being required and unrealistic to expect from every install or even most of them. The guys who say it should be at that level all the time need to visit a cable network in the real world really.

You obviously have other issues there, I run just fine with 5 - 6dBmV on my downstreams so you do need a tech visit.

You didn't mention what your upstream looked like by the way, I would be more interested in that. There's nothing in your downstream numbers to indicate a problem at all. Power, correctable / uncorrectable codewords, RxMER all fine the only odd thing is the differences in power between your 4 downstreams, it's odd for it to go higher then lower but no signs of masses of errored codewords so...

My own levels for reference:

DS-1 DS-2 DS-3 DS-4
Frequency 299000000 307000000 315000000 323000000
Lock Status (QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 1 2 3 4
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate (Msym/sec) 6.952 6.952 6.952 6.952
Power Level (dBmV) 5.51 5.73 5.86 6.23
RxMER (dB) 37.94 38.26 38.61 38.61
Correctable Codewords 942 886 795 598
Uncorrectable Codewords 300 285 305 310

deuse · 05-11-2009, 10:24

Thanks mate

I got a tech coming out next week and I hope my power levels stay good for a whole day

I hope he can sort out why my Downstream levels start at 4-5+ in the morn but by 3pm they are 1.5-2-0 which works for me.
Oh well lets hope.

pabscars · 05-11-2009, 10:33

Just for comparison my 50Meg DS generally stays between 2.9 to 3.9 ish and doesnt venture much past these levels, and at the moment all is well and full warp is achievable captain.

Ive seen it occasionally go over 4 but not very often, However I do have a -3dBmv attenuator on the back.

Broadbandings, do you think there would be any mileage in fitting a -6dBmv instead.

Ignitionnet · 05-11-2009, 12:43

Nah not at all. That's all absolutely fine mate. If it ain't broke...

pabscars · 05-11-2009, 13:07

Quote:

Originally Posted by Broadbandings

Nah not at all. That's all absolutely fine mate. If it ain't broke...

Fairy Fluff

Ignitionnet · 05-11-2009, 13:18

Easy to become obsessed by the power levels but there's a fairly wide operating range precisely because HFC networks aren't an exact science. The levels you deliver to someone next door to the cabinet are quite different from those that are delivered to the person 150 metres from the cabinet.

Rik · 05-11-2009, 13:19

Power Level
(dBmV)9.37 ---- 10.29 -----10.11-----9.67

Connection works fine tho with a -6db attenuator inline

Any cause for concern? is my cable modem going to explode any minute

pabscars · 05-11-2009, 13:24

Quote:

Originally Posted by Broadbandings

Easy to become obsessed by the power levels but there's a fairly wide operating range precisely because HFC networks aren't an exact science. The levels you deliver to someone next door to the cabinet are quite different from those that are delivered to the person 150 metres from the cabinet.

I hear ya big guy, only reason I mentioned it is that times my throughput has been dire, thankfully now its great again.

And put 2 and 2 together to get 5