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#99406 by lbmofo
Thu Aug 23, 2012 6:20 pm
My modem, for the longest time has been like below:

Signal to Noise Ratio 37 to 39 dB
Downstream Power Level -1 to +1 dBmV
Upstream Power Level 40 to 42 dBmV

One day, my SB5101U couldn't get back online any more no matter what I tried.

So I got a new SB6121 and that came online right away.

The problem is with all paramters about the same, now the Downstream Power Level is at +5 dBmV to +6 dBmV. I had a tech come out to take a look. He said he changed the "port" at the street and changed some fittings outside the house and when he left, it was sitting at +3 dBmV but the next day right back to +5 dBmV to +6 dBmV.

For those that may know....what's going on? Is the cable company doing something weird to cause the Downstream to go from perfect 0 to +5, +6?
#99418 by lbmofo
Fri Aug 24, 2012 10:43 am
This morning I found the downstream power to be 7 dBmV. That's a huge difference between what I had at -1, 0, or +1 right? The cable company must be doing something that I dont' know about.
#101380 by lbmofo
Fri Oct 12, 2012 7:33 pm
My downstream is now consistently +9 dBmV... A world of difference between what I used to have. For those of you that know, you think I need to ask my cable company to fix it?
#101387 by murphy
Sat Oct 13, 2012 3:33 am
The specs for an SB6121 are -15 to +15 dBmV.
You could use an attenuator to bring it closer to the center of 0 but

"If it isn't broken, don't fix it."
#101441 by lbmofo
Sun Oct 14, 2012 8:50 am
murphy wrote:"If it isn't broken, don't fix it."

That sounds good.

My speedtest.net tests come back with my expected speeds.

My modem doesn't seem to get knocked off internet too often: System Up Time 17 days 7h:46m:47s

The other modem parameters look good:

Downstream Signal to Noise Ratio 39 dB
Downstream Power Level 7 dBmV
Upstream Power Level 40 dBmV

Phonepower Speedtest comes back good:

Speed test statistics
---------------------
Download speed: 15578 kbps
Upload speed: 1802 kbps
Download consistency of service: 96 %
Upload consistency of service: 95 %
Download test type: socket
Upload test type: socket
Maximum TCP delay: 19 ms
Average download pause: 1 ms
Minimum round trip time to server: 37 ms
Average round trip time to server: 41 ms
Estimated download bandwidth: 31200 kbps
Route concurrency: 2.002736
Download TCP forced idle: 60 %
Maximum route speed: --

VoIP test statistics
--------------------
Jitter: you --> server: 0.5 ms
Jitter: server --> you: 1.2 ms
Packet loss: you --> server: 0.0 %
Packet loss: server --> you: 0.0 %
Packet discards: 0.0 %
Packets out of order: 0.0 %
Estimated MOS score: 4.2
#103192 by lbmofo
Thu Nov 15, 2012 8:43 am
lbmofo wrote:My downstream is now consistently +9 dBmV... A world of difference between what I used to have. For those of you that know, you think I need to ask my cable company to fix it?

Don't know when it reverted back but now, my parameters look better.

Signal to Noise Ratio 36 dB
Downstream Power Level 1 dBmV
Upstream Power Level 37 dBmV
#103931 by lbmofo
Thu Dec 06, 2012 6:51 am
This is without me doing anything and the cable modem parameters look ideal now (SNR, I would like to see higher but....)

Signal to Noise Ratio 35 dB
Downstream Power Level 0 dBmV
Upstream Power Level 40 dBmV

The best part: modem up time is 21 days. Often, with mine and friend's, they can't stay online for more than a day or 2.

I suppose the conclusion is that these parameters could change without end user equipment changing.
#103932 by murphy
Thu Dec 06, 2012 7:20 am
The upstream power level is controlled by the headend hardware. It is adjusted to get the proper incoming power level at the headend. Anything over 50 is cause for concern as it indicates too much signal loss between the modem and the headend. Put a 3 db attenuator in the signal path and the upstream power should increase by 3 db.

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