Seeing OFDM uncorrectables and low upstream power levels on new modem

The image you posted isn't visible. It looks like this:

It's probably because the image requires moderator approval. That might take some time, from a few hours to a day or so. Alternatively, you could upload the image to a file sharing site and post a link to it here, or post text instead of an image.

If you haven't already, please post your Internet plan speed and the following information from your modem or gateway:

• model number
• downstream power levels and SNR
• upstream power levels
• event log

I've added a image link until the pasted image is approved. No new errors in the event log are present. This is a new Arris S33 DOCSIS 3.1 modem.

https://pasteboard.co/JRHV5EK.png

---

@gigabit-seeker wrote: ... Arris S33 modem ... a few days of uptime ... I see some uncorrectables for the OFDM channel and maybe the upstream power levels are low?...

---

If the error counts represent several days of operation, 201 is not an excessive number of uncorrectables. The large number of OFDM correctables seems to be common with DOCSIS 3.1 modems and is probably not a cause for concern.

The upstream power levels are OK -- Comcast's equipment controls them and automatically adjusts them as needed so that the signal they receive is at the proper level.

The downstream power levels for the 8 channels you posted are a bit high, but may not be problematic. It would be helpful to see what the remaining 24 downstream channels look like.

---

@gigabit-seeker wrote:

 and maybe the upstream power levels are low? Is this cause for concern?

---

FWIW, I'll just add this here;

If you got that info from Arris, they are wrong ! They have been passing the buck and have been conning people with that statement lately !! They are probably trying to cover up for their liabilities about the lawsuits against them because of their use of the horrible Puma 6 chipsets... Only the Comcast plant / engineering specs matter;

Specification Min Max
Downstream Power Level
Cable Modems -10dBmV +10dBmV
Gateways and EMTAs -7dBmV +7dBmV
Downstream Signal to Noise Ratio 35dB -
Upstream Power Level +35dBmV +50dBmV
Upstream Signal to Noise Ratio 31dB -
Upstream Receive Power -2dBmV
+2dBmV

Thanks for the help. Here's the complete downstream listing:

https://pasteboard.co/JRInWiw.png 

---

@gigabit-seeker wrote: ... Here's the complete downstream listing:

---

Thanks. As before, the power levels are a bit high, but may not be problematic. 

Are you having any actual Internet connection problems? If not, I'd suggest just checking these values from time to time to see it they remain stable.

---

@EG wrote:

 You have channels that are 31 to 36dB.... Those are below what they recommend... "

Yes, the upstream lower power limits they recommend seem to be about 10 dBmV higher than 35 dBmV.  Everything else Arris recommends seems to match Motorola/Zoom and your values. My 5th channel is showing even lower at 31, hence the concern.

Nope. No nerve. Just reiterating. Arris tech support reps have been telling callers that the upstream power level should be 45dB or higher. And also in their spec link that you posted... We've seen it hundreds of times here in the past, and it continues to this day..... You have channels that are 31 to 36dB.... Those are below what they recommend... "

You stated this: "Regardless, the Arris recommended levels are similar to the levels you posted."

No they are not... Again. They (Arris) are wrong.

---

@EG wrote:

FWIW, I'll just add this here;

If you got that info from Arris, they are wrong !

---

I seem to have touched on a nerve. Regardless, the Arris recommended levels are similar to the levels you posted. 

S33 Cable Signal Levels 

And the S33 uses a Broadcom chipset.

My concern was the OFDM channel uncorrectables and the lower upstream power levels.

But the Arris S33 modem is performing flawlessly otherwise!

 There is no need for "concern".

@BruceW  stated this earlier: " Comcast's equipment controls them and automatically adjusts them as needed so that the signal they receive is at the proper level."

You stated earlier: "But the Arris S33 modem is performing flawlessly otherwise!"

That's the bottom line ! Then don't sweat anything ! Have a good one !  🙂

---

@BruceW wrote:

---

@gigabit-seeker wrote: ... I seem to have touched on a nerve. ...

---

It's just plain wrong of Arris to publish specs that violate the CableLabs standards. If their equipment actually required the upstream levels to be at least +45 dBmV, it would never have been approved and could not be used.

 

---

So to be fair, Arris is simply recommending minimum levels for upstream power that may be too high, correct?

Does anyone have a link to the CableLabs spec that actually shows this discrepancy? I'm happy to contact them to point it out.