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pende_tim
Premium Member
join:2004-01-04
Selbyville, DE

1 edit

pende_tim

Premium Member

[Signals] US Blinking Zoom 5341J Modem

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Too Hot?
Looked at my Zoom 5341J Modem yesterday and the US blue light was blinking. Did the power off/on dance and still was blinking. My speeds tested fine.

After a little Google search I found where someone had fixed this blinking by replacing the splitter. Mine had a 5.5 dB in line with the modem. Since I did mot have a new one, I removed it and wired directly to modem.

The US blinking stopped, speeds are good, errors are nill, however the DS signals look a bit strong.

Any thoughts?

Tobin
join:2003-09-21
Burlingame, CA

Tobin

Member

[Equip] Re: US Blinking Zoom 5341J Modem

The blinking light means nothing, IIRC...it's a bug in the firmware.

Put the splitter back. In fact you're probably better off with a 7dB 4-way splitter

netengineer
@173.8.164.x

netengineer to pende_tim

Anon

to pende_tim
said by pende_tim:

Looked at my Zoom 5341J Modem yesterday and the US blue light was blinking. Did the power off/on dance and still was blinking. My speeds tested fine.

After a little Google search I found where someone had fixed this blinking by replacing the splitter. Mine had a 5.5 dB in line with the modem. Since I did mot have a new one, I removed it and wired directly to modem.

The US blinking stopped, speeds are good, errors are nill, however the DS signals look a bit strong.

Any thoughts?

For reference, you were using balanced 3 way splitter with -5.5dB loss per leg of the split. Unbalanced 3 way splitters have one leg at -3.5dB and two legs at -7dB.

As far as your signals go, your signals are not optimal. The signal is definitely coming in hot. Are you feeding the CM direct from the cable plant tap?

I would look at putting either a 10dB attenuator on their or getting an 8 way splitter with -11dB loss on each leg.

Ideally you want the DS signal to be 0dB and the typical US power would be 42-45dB. Based on your signals, you are quite close to the node on that particular cable plant leg.

Using either methods, your downstream signal would drop to 4-5dB and your upstream would be 45-48dB. Both of those signal levels would be acceptable levels within the RF cable plant for DOCSIS 3.0 using the QAM modulations in use in your particular HFC cable plant.

bradyr
YCCD - Network Operations
Premium Member
join:2008-10-27
Sonora, CA
(Software) pfSense
Netgear CM1200
Ubiquiti UAP-AC-HD

bradyr

Premium Member

yeah my signals were similar to OP's, i'm feeding a cable modem only, about 80-100' from the tap, which is the first tap after an amp (tap is literally connected to the amp, then feeds a small stub on my street). my signals were about +12 DS and 42-43 US.

solution was to put in a 9db cable simulator which brought the levels right about perfect.

telcodad
MVM
join:2011-09-16
Lincroft, NJ

telcodad to pende_tim

MVM

to pende_tim
said by Tobin:

The blinking light means nothing, IIRC...it's a bug in the firmware.

Yes, see: »Upstream Bonding....Flashing US light

flwpwr
@24.113.96.x

flwpwr to pende_tim

Anon

to pende_tim
5.5 versus 3.5 won't fix +14 on the downstream. You have a house amp?

telcodad
MVM
join:2011-09-16
Lincroft, NJ

telcodad to pende_tim

MVM

to pende_tim
said by bradyr:

yeah my signals were similar to OP's, i'm feeding a cable modem only, about 80-100' from the tap, which is the first tap after an amp (tap is literally connected to the amp, then feeds a small stub on my street). my signals were about +12 DS and 42-43 US.

solution was to put in a 9db cable simulator which brought the levels right about perfect.

If you don't have an amp on the modem's feed, as flwpwr asked, then, as your upstream levels are a bit low also, you could probably just use a 6dB or 10dB attenuator at the modem to bring both downstream and upstream back to more normal levels.

Amazon has these (the shipping charges are a bit costly though):

6db Attenuator Pad: »www.amazon.com/6db-Atten ··· 013L48XA

10 DB Attenuator Pad: »www.amazon.com/10-DB-Att ··· 013L56OK

pende_tim
Premium Member
join:2004-01-04
Selbyville, DE

pende_tim to flwpwr

Premium Member

to flwpwr
No in house amplifier.

The levels have been increasing in the past year since my install. Initially with the 5.5 pad, the levels were around 0.0.

I will see if there is a CC truck in the area and try and talk him out of a -10 attenuation pad.
pende_tim

1 edit

pende_tim

Premium Member

Re: [Signals] US Blinking Zoom 5341J Modem

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Made my own -11 dB attenuation pad. The splitter I had that was -5.5 was a 3 port unit.

Moved the dummy cap from port #3 to the feed port, and put the feed from the street onto port 3.

This is what signals look like now. however the blinking light is back.

Speedtests are great, so I guess I will ignore the blinkey light.

Jim721
join:2014-07-31
Belleville, MI

Jim721 to telcodad

Member

to telcodad

Re: [Equip] Re: US Blinking Zoom 5341J Modem

said by telcodad:

If you don't have an amp on the modem's feed, as flwpwr asked, then, as your upstream levels are a bit low also, you could probably just use a 6dB or 10dB attenuator at the modem to bring both downstream and upstream back to more normal levels.

Attenuation will help downstream but wont do anything for the upstream the numbers seen by the modem will look better but its false because after the attenuator the upstream will still be low.

telcodad
MVM
join:2011-09-16
Lincroft, NJ

telcodad

MVM

said by Jim721:

said by telcodad:

If you don't have an amp on the modem's feed, as flwpwr asked, then, as your upstream levels are a bit low also, you could probably just use a 6dB or 10dB attenuator at the modem to bring both downstream and upstream back to more normal levels.

Attenuation will help downstream but wont do anything for the upstream the numbers seen by the modem will look better but its false because after the attenuator the upstream will still be low.

Yes, you're correct, the modem will just increase its transmit power to compensate for the added upstream attenuation. The signal level on the other side of the attenuator will still be the same as without it.

Actually, the OP's upstream power levels of about 37 dBmV, while a bit low, is still above the 35 dBmV recommended minimum: »Comcast High Speed Internet FAQ »What should my Signal Levels be?

Personally, I like to shoot for the low 40s.

The reason why it's not good for the upstream power to be too low is due to the relatively high amounts of ingress noise that typically enter the cable system at a customer's location, which then leads to a poor upstream SNR (uSNR) result. See: »Re: [Signals] Upstream signal doesn't look great?

Kasoah
join:2013-08-20
Merced, CA

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Re: [Signals] US Blinking Zoom 5341J Modem

37dbmv should be fine considering how strong his signal is.

telcodad
MVM
join:2011-09-16
Lincroft, NJ

telcodad

MVM

said by Kasoah:

37dbmv should be fine considering how strong his signal is.

So, maybe the OP just needs to add a 10dB Forward Path Attenuator (FPA).

PPC is one of the companies that makes them: »www.ppc-online.com/Produ ··· ning.cfm

There's also this previous thread of yours: »[Connectivity] Signal attenuator for downstream

Jim721
join:2014-07-31
Belleville, MI

Jim721

Member

said by telcodad:

So, maybe the OP just need to add a 10dB Forward Path Attenuator (FPA).

Yep thats what the OP needs. I have a few of them i got from a tech i stopped on the road he had a box of them 3db,6db and 9db they can even be piggy backed if needed and they dont touch the upstream one bit.

gr33dy
join:2002-05-31
Albuquerque, NM

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I wish Comcast would push some new firmware for this modem to correct this issue.. it's annoying as hell.

Jim721
join:2014-07-31
Belleville, MI

Jim721

Member

said by gr33dy:

I wish Comcast would push some new firmware for this modem to correct this issue.. it's annoying as hell.

Its not just comcast, Zoom would also have to play a roll in this. I am not sure if comcast or Zoom is aware or even cares about the issue because its not impacting performance. But yes it would be nice if was fixed.

Sootycapped
@69.247.117.x

Sootycapped

Anon

It has nothing to do with the Zoom. As soon as Comcast fixes the issue in your area, the blinking led will stop. Nothing can be done until them.

Jim721
join:2014-07-31
Belleville, MI

Jim721

Member

said by Sootycapped :

It has nothing to do with the Zoom. As soon as Comcast fixes the issue in your area, the blinking led will stop. Nothing can be done until them.

Zoom and Comcast have to work together for a new firmware. Are you saying this is not a firmware issue rather a stand alone comcast issue ?

jbob
Reach Out and Touch Someone
Premium Member
join:2004-04-26
Little Rock, AR
·Comcast XFINITY
Asus GT-AX6000
Asus RT-AC66U B1

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FYI....I've been seeing the issue here for a while now. Matter of fact I was the OP in one of the linked threads in this thread. After a while I basically just ignored the flashing US light. Over time it would all by itself quit flashing. After some time it finally became steady and remained that way for several months.

Recently it has began to flash again. I don't seem to be having any connection/speed issues although I am trying to run down another intermittent issue but I don't think the two are related.

Sootycapped
@69.247.117.x

Sootycapped to Jim721

Anon

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My modem has stopped doing this after changes to the Comcast infrastructure. I am still running the same firmware, 5.5.8.6J, and nothing else has changed on my end. I did not even have to reboot. No difference in performance, but does indicate problems from Comcast.
SPOOZ
join:2011-06-20
Lafayette, CO

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I noticed my upstream light finally stopped blinking.
I looked in the modem log and saw this:

Priority: Critical (3)
Description: 16 consecutive T3 timeouts while trying to range on upstream ...
johnfc
join:2002-11-23
Gaithersburg, MD

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I solved this by putting a piece of dark tape over the lights they are too bright anyways. Speed up and down is ridiculous on the extreme 150 service. As long as performance is up to snuff this is really not an issue is it?