[SOLVED] Cable modem losing downstream channels

[J1983]

Hey,


For years I have had isp issues with my cable internet. New modems, routers, and lines inside and outside house haven't helped. Recent months it has been especially bad.

In the evening, speeds go down to around 5 Mbps or below but are supposed to be 75 mbps. Dozens of tech visits haven't helped until last week. A bucket truck showed up and fixed an issue where my modem was only showing 9 of the usual 16 downstream channels. It stayed showing 16 channels for a few days after the tech left, but tonight it is back down to only 9 channels again and also the really slow speeds. Downstream channel power levels are around 10-11 dbmv. Upstream is around 40-43 on both channels. SNR stays around 40.

Last winter I always lost internet and channels when it got cold out and the power levels would go way out of range, but like I said, the power levels stay pretty steady now whenever I look, so they must have fixed a little of the issue at some point. Weird thing is, my upload usually stays around 7 mbps which I think is around what it should be.

Also, my modem only started losing these 7 channels for about the last month or so. It does not seem to be happening only when it is really cold now though as compared to last winter because right now it is in the upper 60's Fahrenheit, so the temperature doesn't seem to be the problem to me but I could definitely be wrong.

As far as I know, my section of the tap only has me and one other property where the house burned down years ago, so no one is on that property anymore.

The last tech that finally solved my lost channel issue for a few days said he had to balance a couple of amps I believe. He has been here several times over the last couple of weeks. One important point he did make was, he said his previous visit a few days before the last one, he said he adjusted the amps, but after he came back a few days later, he noticed they were off by around 5 db from what he had them set at previously. So I guess the amps apparently came out of adjustment on their own for some reason.


ANY help at all is definitely appreciated. Thanks

 

[gggplaya]

Do you have satelite tv or anything MOCA in your house?

Are you running straight from the outside line to your cable modem with NO splitters?

 

[J1983]

Do you have satelite tv or anything MOCA in your house?

Are you running straight from the outside line to your cable modem with NO splitters?

Hey thanks for the reply. I don't have satellite TV, only cable TV and internet. The line that runs from the tap comes over to my house and then splits into two lines before it comes inside my house. One line that comes into the house is going straight to my modem. The other line has a splitter inside that splits to different TV's and I also tried it but it didn't help.

 

[gggplaya]

The only thing left to do is change out the modem, maybe the transceiver is flaky. But that's a long shot.

Are you renting the modem from them, or did you buy your own?

 

[J1983]

I own the modem. I have had several the past several years but they never fixed my issues. A tech even tried one of theirs a few months ago but it didn't fix anything either, but that call may have been only for the slow speed, but not losing channels on the modem though, I don't remember.

The last time I remember losing channels was last winter when it lost channels and only worked when it was warm out a few hours each day. The issue did disappear for these last few days though like I said, but whatever the tech adjusted must have just messed back up though. At this point, I honestly can't count how many dozen tech visits there have been.

I'll let you know what happens after the next visit. I might just try a new modem again like you said because you never know.

Thanks again

 

[gggplaya]

I don't think there's really anything else you can do other than check all the connections outside your house and make sure nothing is corroded.

It's pretty simple what's inside your house, 1 split then straight to modem, and if you make sure everything on your side is solid, then the problem must be on the ISP side of things.

Can you log into your modem and copy and paste the channels with their SNR and their power strength?

 

[J1983]

Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR	Corrected	Uncorrectables
1	Locked	QAM256	43	393000000 Hz	10.4 dBmV	39.8 dB	0	0
2	Locked	QAM256	25	285000000 Hz	11.4 dBmV	40.6 dB	0	0
3	Locked	QAM256	26	291000000 Hz	11.6 dBmV	40.8 dB	0	0
4	Locked	QAM256	27	297000000 Hz	11.6 dBmV	40.7 dB	0	0
5	Locked	QAM256	28	303000000 Hz	11.6 dBmV	40.6 dB	0	0
6	Locked	QAM256	29	309000000 Hz	11.6 dBmV	40.7 dB	0	0
7	Locked	QAM256	30	315000000 Hz	11.6 dBmV	40.6 dB	0	0
8	Locked	QAM256	31	321000000 Hz	11.5 dBmV	40.5 dB	0	0
9	Locked	QAM256	32	327000000 Hz	11.7 dBmV	40.8 dB	0	0

Upstream Bonded Channels
Channel	Lock Status	US Channel Type	Channel ID	Symbol Rate	Frequency	Power
1	Locked	ATDMA	2	2560 Ksym/sec	20800000 Hz	42.5 dBmV
2	Locked	ATDMA	1	5120 Ksym/sec	26000000 Hz	42.8 dBmV

 

[kanewolf]

Your input power at +10dB is actually kind of high. +3dB is the typical target value. 40dB SNR is good.

 

[gggplaya]

Everything looks fine, I would view that chart when you have a dropout.

 

[J1983]

Weird thing is, those numbers stay pretty well the same, even when the speeds go way down. The osp tech that fixed the issue for a few days said he looks for anything +15 or below, but a different tech that usually just does inside stuff said 7 or below is a good number. The highest I usually see is about +11.6 on the downstream.

 

[J1983]

So bucket trucks came out and have been working on the road I live on. Several of the guys have told me there is a lot of noise in the lines in the area and a lot of it is coming out of peoples houses. One guy went outside my house to hook into the line to show me on his meter. The graph was all over the place and he said it is supposed to be flat. Just wondering how they will solve this. Also, is there anything that I can buy that doesn't cost a ton of money to see the noise like he did. The reason I ask is, if I ever change lines or anything in the future, I would like to know if I create any interference in the process.

Thanks

 

[bill001g]

In many cases there are filters placed on the line as it enters your house. Many times it is combined with the grounding block they must place on your house. It looks like a simple coax connector but it can be much more. The most common thing you would see being sent out is things like MoCA. It runs on different channels but it is not suppose to be sent outside your house, both because it could cause issue for others but also you don't want your network extended outside even though it is encrypted.

Unfortantly those meters all seem to cost a ton of money. Not sure which ones the cable company uses lately but the ones used to test/install ethernet cables start at about $500 and go up.

 

[J1983]

So another tech came out and tried one of their modems. When he tried his, it connected quick and with 24 channels. He said my area only uses 24. While he was here, my modem was taking a few minutes to lock in and it was still only getting 9 of its 16 channels.

My question now is, he says he thinks it is the modem, but every time they come out and balance the amps or anything, I usually get my missing channels back for a day or two. Even a few minutes before he got to my house yesterday, my TV and internet both went out for a few minutes. When they came back on I had my missing channels back again until he got here and restarted my modem. He said the reason the service went out for a few minutes was because he was down the road I think at the node doing a speed test, I guess to see if the main lines are up to par or whatever. He said he didn't fix anything though so he didn't know how I got my channels back for a few minutes. So if my modem is bad, how do I get missing modem channels back when they mess with the amps and everything. Like I said though, while he was here, his modem was locking in on all channels when mine wouldn't.

I have been through several modems over the years for low speed issues that were never resolved which is why I am hesitant to buy yet another one.

Thanks for any suggestions

 

[bill001g]

When you start having issues like this maybe rent the modem from the cable company for 6 months. You could then try to reinstall your own and see if things stabilized.