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pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3

[Signals] Balancing my own signal

Currently my signals look roughly like this with a forward-path-only pad of some kind (doesn't affect US power levels):

down_channels: 8
down_power: 1.2 2.2 1.9 1.7 1.3 1.1 1.4 1.0
down_snr: 34.0 34.7 34.5 34.3 33.9 33.7 34.2 33.6
up_channels: 3
up_power: 41.7 41.7 41.7 NaN

Removing this device, the DS power goes up (as expected), but the SNR is quite a bit better (~1-1.5 dB):

down_channels: 8
down_power: 9.0 9.3 9.1 8.9 8.7 8.5 9.1 9.0
down_snr: 35.4 35.6 35.6 35.2 35.1 34.9 35.6 35.0
up_channels: 3
up_power: 41.5 41.5 41.5 NaN

I've seen some minimal packet loss and such, which is affecting some things slightly.

I'd leave the device out, but then the downstream power is at 9 dB and when it cools off at night it'd be well over +10 dB. Would it make sense to add a splitter to knock the downstream down 3.5 dB which would hopefully not affect the DS SNR as much. I know over 33 is fine, but lately it's been dipping below 33 at times and I figured another 1-1.5 dB of SNR padding would help for those times when it dips a bit low.
--
"I drank what?" -Socrates


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5

You are fine in either respect, I would not worry about "balancing" anything. Leave the pad on, your problem most likely lies elsewhere. If your SNR is dipping that low, you may have a wiring issue going on. The only way you will ever know, is to schedule a service call and let the tech check things with his SLM.

You are watching your signal levels too closely.



pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3

said by beachintech:

You are fine in either respect, I would not worry about "balancing" anything. Leave the pad on, your problem most likely lies elsewhere. If your SNR is dipping that low, you may have a wiring issue going on. The only way you will ever know, is to schedule a service call and let the tech check things with his SLM.

You are watching your signal levels too closely.

I already know your opinion of what I do with my signal. I AM seeing packet loss, as I've mentioned.

My question is simple: is it worth swapping the pad for a splitter, thus putting my US up near 46 in order to keep DS SNR higher?

You can chose to ignore the question, that's fine. But the critiques of what I'm doing with my own connection that I pay hard-earned money for are not welcomed.
--
"I drank what?" -Socrates


Johkal
Cool Cat
Premium,MVM
join:2002-11-13
Happy Valley
kudos:10

1 recommendation

I'd rather have the US at 46 to improve DS SNR. I would say do it.



pflog
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El Dorado Hills, CA
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said by Johkal:

I'd rather have the US at 46 to improve DS SNR. I would say do it.

I suppose I can change it for a few days and see if the packet loss subsides. 46 still has some margin for US channel bonding on D3, right?
--
"I drank what?" -Socrates


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5

1 edit

Yes, about 4 DB, assuming your modem is reporting proper signal levels.

I would skip the splitter. It will not hurt anything either way. Make sure you properly terminate the unused ports. Wouldn't want to hurt the SNR further.

I think your opinion of my comment is off from the intention. Your packet loss may not be related to marginal signal. Until you follow through involving a tech with a real meter, there is no way to say otherwise.

Good luck as always.



Johkal
Cool Cat
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join:2002-11-13
Happy Valley
kudos:10
reply to pflog

You have the room with 46. 3-4 increase won't hurt a thing if it slides. Go ahead and experiment.



pflog
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El Dorado Hills, CA
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1 edit
reply to beachintech

said by beachintech:

Yes, about 4 DB, assuming your modem is reporting proper signal levels.

Yeah, I'm aware now (thanks to you from another thread) of the possibility the modem is misreporting it. I'm planning to call to get the CMTS numbers to see if they jive. Or are the CMTS numbers also suspect?

I would skip the splitter. It will not hurt anything either way. Make sure you properly terminate the unused ports. Wouldn't want to hurt the SNR further.

I did have an attenuator from my FiOS install (signal was too hot for the S3 Tivo), I may have to use that as I don't think I have any terminators.

I think your opinion of my comment is off from the intention. Your packet loss may not be related to marginal signal. Until you follow through involving a tech with a real meter, there is no way to say otherwise.

I'm not disputing that it could be unrelated, but the packet loss didn't start occurring until recently when the SNR has fluctuated and dropped into the 33's (and occasionally down into the high 32's). Cause. Effect.

--
"I drank what?" -Socrates
Expand your moderator at work


pflog
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El Dorado Hills, CA
kudos:3
reply to beachintech

Re: [Signals] Balancing my own signal

Thanks, I'll call to see if their numbers at the CMTS jive with the modem. Can those be trusted, or is the meter on the prem the only legitimate numbers to trust?

Speaking of terminators...I have a 4-way splitter with them on there but wanted to move them to my 2-way splitter (or a 3-way with a -3.5dB leg) but do I need a special tool to remove the terminators?
--
"I drank what?" -Socrates



beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5

Meter is really the best number, modem will get close, but i've seen some be off by a good bit. You also get a lot more info than a number with a meter.

Are they locking terminators? If they are, yes you do, they can be had online pretty cheap. You can buy non-locking terminators as well very cheap.



pflog
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El Dorado Hills, CA
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said by beachintech:

Meter is really the best number, modem will get close, but i've seen some be off by a good bit. You also get a lot more info than a number with a meter.

Are they locking terminators? If they are, yes you do, they can be had online pretty cheap. You can buy non-locking terminators as well very cheap.

Thanks, I'll look around for some non-locking ones or purchase the tool and leave things as-is until I am able to properly terminate the unused connections on the splitter.

Just for everyone edification, I'll post the numbers this Netgear D3 device is reporting vs. the ones read from the CMTS so we can see how close this modem reports them (although I guess the degree to which they are accurate may vary over time, too, relative to the CMTS).
--
"I drank what?" -Socrates


pflog
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El Dorado Hills, CA
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Well, take it with a grain of salt but the CMTS side shows the same US power (41.7), the same SNR (34.1) but the power level on their end is showing -1 whereas most of my channels are showing +1 on the modem's DS PWR.

So if they're off by 2 (again, assuming the CMTS is correct) then maybe I would be ok with taking the pad out entirely and sitting at +9 (+7 according to the CMTS).

I guess I'll give that a go for a bit until I can hook up the splitter

Thanks for both of your responses and info!
--
"I drank what?" -Socrates



beachintech
There's sand in my tool bag
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kudos:5

Was that downstream power or upstream receive power? Did you happen to ask what your upstream SNR was as well?



pflog
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El Dorado Hills, CA
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said by beachintech:

Was that downstream power or upstream receive power? Did you happen to ask what your upstream SNR was as well?

That was downstream power I believe.

Doh! I meant to ask about the uSNR, but got distracted by my kids coming home. I'll call them back to ask in a few. Thanks for the reminder.
--
"I drank what?" -Socrates


EG
The wings of love
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join:2006-11-18
Union, NJ
kudos:9

They gave you the wrong numbers as they usually do...



pflog
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El Dorado Hills, CA
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said by EG:

They gave you the wrong numbers as they usually do...

What exactly am I asking for when I call to get the right ones? I specifically asked for the numbers at the CMTS.
--
"I drank what?" -Socrates


EG
The wings of love
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join:2006-11-18
Union, NJ
kudos:9

You are asking for the correct info its just that many if not most of the phone reps do not know what they are looking at.



pflog
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El Dorado Hills, CA
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Upstream SNR is 36.1. I asked if he was sure that was the upstream and then asked for the downstream and that's 35.8 (which jives with my modem's reported DS value).
--
"I drank what?" -Socrates



EG
The wings of love
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join:2006-11-18
Union, NJ
kudos:9

Many times they quote the stuff polled from the modem, not the CMTS.



pflog
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El Dorado Hills, CA
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said by EG:

Many times they quote the stuff polled from the modem, not the CMTS.

Ahh ok.
--
"I drank what?" -Socrates


EG
The wings of love
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join:2006-11-18
Union, NJ
kudos:9

To me this is not surprising considering the typical training (or the lack thereof) of some of their employees...


Jeremy W

join:2010-01-21
reply to pflog

I don't know what kind of modem you have, but Motorola modems show counters for errored and unerrored codewords. Those counters would give you a much better idea of whether or not your packet loss is occurring on the coax or not.

My strong feeling is that the issue lies elsewhere. Your SNR is nowhere near bad enough that you should be seeing issues.



pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3

said by Jeremy W:

I don't know what kind of modem you have, but Motorola modems show counters for errored and unerrored codewords. Those counters would give you a much better idea of whether or not your packet loss is occurring on the coax or not.

My strong feeling is that the issue lies elsewhere. Your SNR is nowhere near bad enough that you should be seeing issues.

Unfortunately, Comcast has dummied down the customer-facing side of the SMC and Netgear (with the same web UI) so this info isn't visible. The telnet interface probably has a way to query this, but customers don't have access to that either.
--
"I drank what?" -Socrates


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9
reply to Jeremy W

said by Jeremy W:

Your SNR is nowhere near bad enough that you should be seeing issues.

Have you taken in to account the uSNR ???

The Codeword errors as read at the modem are for the downstream only..


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5

the Upstream SNR isn't that bad, if the numbers were correct.



flwpwr

@comcast.net
reply to pflog

down_snr: 34.0 34.7 34.5 34.3 33.9 33.7 34.2 33.6

35 is the cutoff for MY ffo, not sure about yours, but that would be of concern on my jobs. Now I am not saying it is for you, some plant just runs different but generally you want 35+ on DSNR, and 30+ on USNR. It is extremely uncommon to have a better USNR than DSNR. You are reporting 36 USNR and 34+- DSNR, that's not normal. I have however seen modems that report their SNR just flat out wrong [freaking zoom and cisco], whether that is your case or not, is hard to say it could be, or it may be an actual issue. If you take the forward only attenuator off, what happens to DSNR? The device may just be introducing noise, normally I would suspect a active device like a house amp [hate you so much on-q 8/16 port amps] but bad wiring is bad wiring, inside a passive device or not. Cable simulator I believe is what they call those things, never had to use one, and as to the splitter question yes but you need to TERMINATE the unused ports.

As to testing the packet loss becasue that issue may very well have NOTHING to do with it, ping the gateway address [ipconfig /all] with -t, and leave it for a while, in the back ground, and then see if you are getting packet loss just on your side of the network to the modem or not. If you are, something else is causing the issue other than cable because that pings on the Ethernet/wireless side only up to the modem itself, which could be faulty.

You can also use the line quality test here to test just to the modem on cable side IIRC as it uses the public IP to determine its target.



pflog
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join:2001-09-01
El Dorado Hills, CA
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said by flwpwr :

down_snr: 34.0 34.7 34.5 34.3 33.9 33.7 34.2 33.6

35 is the cutoff for MY ffo, not sure about yours, but that would be of concern on my jobs. Now I am not saying it is for you, some plant just runs different but generally you want 35+ on DSNR, and 30+ on USNR. It is extremely uncommon to have a better USNR than DSNR. You are reporting 36 USNR and 34+- DSNR, that's not normal.

I have however seen modems that report their SNR just flat out wrong [freaking zoom and cisco], whether that is your case or not, is hard to say it could be, or it may be an actual issue. If you take the forward only attenuator off, what happens to DSNR? The device may just be introducing noise, normally I would suspect a active device like a house amp [hate you so much on-q 8/16 port amps] but bad wiring is bad wiring, inside a passive device or not. Cable simulator I believe is what they call those things, never had to use one, and as to the splitter question yes but you need to TERMINATE the unused ports.

The techs that have come out in the past didn't seem concerned at all, even by 33 dB, even when I flat out say that I think it's low. I'm actually quite happy that I'm at ~35 right now instead of 33. I was at over 37 and a while back they did something at night and I dropped over night from 37 to 34/35 and it's been there since.

When I remove that pad, the SNR does go up by 1-1.5 dB. So even though my DS power is > 10 at the moment (due to colder temps over night), the connection seems fine. The CMTS reported DS power was actually 2 dBmV lower than what my modem says, so I'm hoping my "11 dBmV" right now is actually 9 dBmV.

As to testing the packet loss becasue that issue may very well have NOTHING to do with it, ping the gateway address [ipconfig /all] with -t, and leave it for a while, in the back ground, and then see if you are getting packet loss just on your side of the network to the modem or not. If you are, something else is causing the issue other than cable because that pings on the Ethernet/wireless side only up to the modem itself, which could be faulty.

You can also use the line quality test here to test just to the modem on cable side IIRC as it uses the public IP to determine its target.

I was using smokeping to gauge but unfortunately realized it had stopped running on the 20th. So I restarted it on my end now that I have the pad removed to see how the smokeping graphs look.

I guess I can have someone out, but the installers left my modem running with a SNR of 32.5 and I had to have a trouble call out a week later. Then a year later when the temps started warning up, I started having a low SNR and drops and it took many visits and escalating to business escalations to get them to come out. They rebalanced something and the down SNR was better, but still I had issues with random drops (which turned out to be upstream noise bursts).

And during the latest visit, the gut rewired my point of entry connection to give the cable better curves (it was tightly almost kinked before) and added this pad, the sum of which was a worse signal (at least according to the numbers reported on the modem).

So you can see why I'm hesitant to involve them, especially if it means I'll have to pay for a truck roll that finds nothing wrong.
--
"I drank what?" -Socrates


news

@videotron.ca
reply to flwpwr

Personally, I would'nt install any attenuator if your SNR is better without. It doesn't really matter if you have +9 or +10 dB downstream level with a SNR about 35-36 dB. It's not really different from having a -9 or -10 dB downstream level with a 35-36 dB SNR. Docsis specifications are +15 to -15 dBmV. If you have +10 downstream level but 33-32 SNR, it's another story, there's probably an overdrived amplifier somewhere on the cable plant...

I remember the hold Motorola proprietary cable modem (not docsis) with a downstream specifications between 0 and -10 dBmV...

I just cheked my signals right know, my downstream power level is +5 with 36 dBmV SNR. This winter, my signal was +11 dB with also 36 dBmV SNR, there's probably an amplifier that isn't in Automatic Control Mode (AGC), who cares? My signal are within ranges anyway....