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Signal strength

Contributor

Signal strength

I have had gigabit internet for a few weeks now and was able to successfully activate it over the phone. Comcast still sent a tech out anyways and the tech installed an in line amp. I do get full speeds at times but I noticed when I run 2 speed tests back to back wired and the first test comes 950 Mbps down then the second test may only be 600 Mbps. It seems like my speeds fluxuate a lot. My signal does seem a little high but the tech said I needed it for the gig speeds. Below are my signals. It seems like I have a ton of uncorrectables. And on this screenshot my modem was probably only up for 2 or 3 days.

Modem is an arris SB8200
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Contributor

Re: Signal strength

Well any guesses.
Contributor

Re: Signal strength

should i add a splitter or remove the amplifier the tech installed?

Diamond Problem Solver

Re: Signal strength

Depending on the type of amp that it is, and whether or not it has an *active return*, give it a try. The forward downstream power is indeed high.
Contributor

Re: Signal strength

It’s a commscope home connect/subscriber amplifier. Model CSMAPDU5VP. The weird part is how much my signal changes. A yesterday my 3.0 channels were between 6-8 dBm with my 3.1 channel hitting 9 but a few days ago my 3.0 channels were running between 9.5-12 dBm with the 3.1 channel hitting 13. Upstream channel always stays between 46-47.5 dBm. The strength of the signal is always different. I should also note that I have 1 cable line going into the house that is split off. I line goes to my gig modem and 1 tv the other line goes to my wife’s business plan modem that is only hard wired to one computer (yes I know it’s dumb but her employer requires her to be connected to the business plan modem only). The highest I have ever seen the channels run are the 3.0 channels run from 11-13 dBm with the 3.1 channel hitting 14.5. I don’t think I have ever seen anything go over 15. The snr/mer always stays between 37-39
Diamond Problem Solver

Re: Signal strength

Seems that you are focusing on 15 dB, and I can understand why, but you shouldn't. That is a manufacturers figure. The Comcast system specs are different. Ideally, it should be under 7dB. 0 dB is the perfect number.

 

For giggles, have you tried bypassing it ?

Contributor

Re: Signal strength

Yes. Prior to the in line amp being installed by the tech it was working. I did order a 6 and 10 dBm attenuators from Amazon today to see if I can knock down the power. Here it is this afternoon today. Most channels are between 10 and 12 today. I’m guessing I would be best to try the 10 dBm attenuators first if my goal is to get closer to 0. Lastly the attenuator has both female and male ends. I was going to put it directly on the output of the in-line amp then attach the coax to that then the modem or am I better off putting the attenuator on the modem itself then attaching the coax to that. I talked with Comcast again today and they don’t seem concerned at my power levels running between +10 and +15
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Contributor

Re: Signal strength

Also all thoes correctables/uncorrectables are after the modem being online for only 7 hours.  between the fluxuation of power levels and all the correctables/uncorrectables is it possible the modem is bad.  Its the Arris SB8200,  Im asking because im nearing the end of my return window.  Also I woke up this morning and my modem had reset around 5am on its own and i was only getting speeds betweed 20-30 Mbps.  Tried resets on both my router and modem with no luck.  comcast had to reprovision it to get it back to normal.  

Contributor

Re: Signal strength

I guess I will just have to play with the setup and see what happens

Contributor

Re: Signal strength

Here are my signal strengths today. Any suggestions on which attenuator I should use. I have a 6 and a 10 dBm
85C4567C-0B47-420E-B54D-46655B485728.png
Diamond Problem Solver

Re: Signal strength

Is the amp removed from the modem line ? If not, remove it. If it is, try the 6 dB pad. The 10 dB pad will push the upstream power too high / out of spec.

Contributor

Re: Signal strength

No,  the in-line amp that the tech installed is still there. I’m assuming because the signal coming into the house isn’t strong enough to supply 2 different modems and a tv. 

 

Is it normal for the signal to fluxate that much.  My 3.0 channels will be 5 dBm one minute then 10 dBm a minute later. My 3.1 channel fluxates from 10 dBm to 16 dBm.  

 

Im also afraid to mess with it now because because my correctable/uncorrectables are under 50 on all channels are under 50 when they were in the thousands 

 

lastly my speed tests don’t make sense. The Speedtest app on my Mac hardwired always says between 900 and 930 Mbps with a ping of 3, the speedtest.net website says between 600 and 900 Mbps, the xfinity speed test shows the slowest speeds between 400-600 Mbps with a ping of 11 but this should be the fastest.  I have tried safari, chrome, and Firefox 

Diamond Problem Solver

Re: Signal strength


@JoeInPa wrote:

No,  the in-line amp that the tech installed is still there. I’m assuming because the signal coming into the house isn’t strong enough to supply 2 different modems and a tv. 

 

Looks like it is "strong enough" to me.

 

Is it normal for the signal to fluxate that much.  My 3.0 channels will be 5 dBm one minute then 10 dBm a minute later. My 3.1 channel fluxates from 10 dBm to 16 dBm.

 

No it's not normal. That is a problem that may be beyond your premises. 

 

Im also afraid to mess with it now because because my correctable/uncorrectables are under 50 on all channels are under 50 when they were in the thousands

 

It's your choice. Good luck with it !


 

Contributor

Re: Signal strength

So i tried the 6 dBm attenuator and the signal strenghts dropped to 4-6, however the upstream went up to 55.  My speeds dropped to around 50 Mbps.  Took the attenuator off and powercycled the modem and the power levels went back up to 12-14 dBm but the speeds went back to normal.  Guess i wil just keep it on like normal and deal with the fluxating signal strength