Unstable Line - Does Anyone Know Why or How ?

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phatboy

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Hey Guys

I have spent a wonderful 2 years or so on a 4MEG ADSL line. I have Mweb Uncapped and this has been a dream. Until about 3 months ago. Mweb are great and I have no issue there. The problem lies with Telkom.

My line used to sync constant and always at 4096k. Exactly 4meg and worked great, download speeds of over 400kb/s constant and everything was great. Until Telkom did something in the background or in the exchange, now my line suddenly is syncing at only 3840 and fluctuates between 3600 and 3900 kbs. It's driving me insane, because not only is the sync speeds fluctuating, my download speeds jump around when downloading big files sometimes going as far down as 150kb/s and then back to 380kb/s. But i never achieve over 400kb/s anymore.

I have changed my router out, I have put new pots filters in, i have disconnected my alarm from the line, i have replaced the cable from the router to the wall. I have logged 2 faults with telkom and they say the line is fine and cannot see an issue. They lied and told me the DSLAM got flooded during the storms and they were rebuilding it. That has been done now and still same S#@! on the line. Its driving me insane. Check out my router stats below. The attenuation is great, but the SNR Margins are a little low, because those used to be great as well. As a result of this situation as well, my exchange is now 10meg capable and i cant go anything higher than 3.9 meg due to the line issues, and i'm sure than if i fix my line ill be able to achieve better speeds.

Anyone got any suggestions ?

ADSL Link Downstream Upstream
Connection Speed 3744 kbps 512 kbps
Line Attenuation 30.0 db 19.0 db
Noise Margin 6.1 db 10.0 db

PLEASE HELP ME !
 
The noise margin is quite low given that the attenuation isnt bad at 30db. Did you request a port reset? And then ask them to drop ur line to 3Mbps to test stability. Been there done that (and still on 3 with a 10Mbps exchange)

To compare, my attenuation is at 52, noise margin at 12 running 3Mbps. Thx Telkom
 
Yeah that's why your line is only at 3Mbps. Your attenuation is reaching limits.

My attenuation according to telkom and other websites, is excellent. if you have 30 or under you have an incredible line. Problem is anything lower than 6 on noise margin, and your line starts dropping or your speeds start being affected. My SNR on downstream used to sit at about 18 which is 10mbps capable.

Anyways, yes i've done 2 port resets, they didnt help. the line resynced at 4096k for about 5 minutes then goes back to being crap. Stability at 3mbps, yes i tried that, it does stabalize at 3mb. I don't want 3mb, i had 4096K constant for like 2 years, so why all of a sudden can it not be 4meg. I am only 1.6km from my exchange too
 
phatboy, exactly which modem are you using right now, and what exact other modems have you tried?

The thing about ADSL modems is, if all the ones you tried are based on the same chip, they will all give you the same results.

You can get the details of modems from: http://bc.whirlpool.net.au/bc/hardware/

Currently my favourite on the Telkom 10mbit exchanges are the Billion 7402X (no wireless but not really cheap). I have seen these modems keeping their sync stable on terrible lines with a SNR of 5.0. (I must add here, I didn't make a typing mistake, and I am fully aware that you actually need a SNR of 6.0 to really sync, but these really can sync at a SNR of 5.0)

According to the above link, it uses a Conexant - Solos chip.

Now I am currently on a ADSL1 exchange, using a Billion 7300RA, its a real cheap modem, and works rock solid on the ADSL1 exchanges, but once you move to the 10mbit capable exchanges, these specific modems all off a sudden start showing funny things, ie. on a 384 line they sync at 380/120 instead of 384/128, they dynamically change their sync rates ect and generally doesn't give the most stable experience. According to the above link it uses a Trendchip chip, which IMHO is not the best chipset for our newer ADSL2+ exchanges in SA.
 
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I'm currently using a Netgear DG834GT.

I have also tried the custom netgear firmware from the DG Team which didn't help.

I tried the following as well.

Telkom Mega100WR. Makes no difference.
Linksys(dont' remember the model, but I have it at home I will check). No difference.

My router does dynamically change sync rate though, i can see this when watching the sync speeds and they change now and again.

I do have a billion of some sort, don't remember the exact model either, haven't tried it yet because it has no wireless but maybe i should try it. But you are right, it seems to be ever since my exchange was made 10meg capable that i'm having these issues. Maybe this is the problem.
 
@Tinuva, I think some modems report the SNR margin as the actual SNR value - 6dB, because its impossible to sync at anything below 6dB. So it could be that the Billion 7402X would report the SNR margin as 5.0dB when it is in fact a SNR of 11.0dB?

@phatboy:
Those SNR margins are terrible considering that you have a line attenuation below 40dB! Usually the SNR margins are that bad when the line attenuation is 45dB or higher.

I would suggest that you also try connecting your ADSL modem directly to your Telkom line - without any filters or other telephonic devices connected, and then check your SNR margins & sync speeds again.
You can also try to switch between ADSL2+ and G.Dmt modulation.
If none of the above made any real difference, I would suggest that you try to borrow a decent ADSL modem first, before just buying one that might end up making no difference either.

If you're willing to spend that much on an ADSL modem (like what the Billion 7402X costs), then rather go for the Siemens Gigaset SX762.

There are also very good cheap alternatives, like the D-Link DSL-2500U (under R200 incl VAT) and the TP-Link TD-8840 (R219 ex VAT at Uniterm Direct). Unfortunately they don't have WiFi.
If your current ADSL modem includes a WiFi AP, then you can simply chain it to one of those ADSL modems to provide WiFi access.
 
Noise Margin 6.1 db

When that drops below 6... there are sync issues... even if the modem is still synced.. error correction on the modem and DSLAM can make downloads very unstable...

There is noise on your line... Something started causing it... there are a lot of factors... your router's power supply... something "new" in the house.. like a fridge or a fountain pump... etc. etc... unplug your house one by one and see in that 6.1 increases...

otherwise its not something you can do anything about... your last resort is to fix the SNR (im not sure for your modem but google it..) to 6.5... the modem will sync at a lower speed but at least it will be stable and you will get full speed of whatever its syncing at... this will at least give you stability while you chase the noise generator.

I have found though, that Telkom techies are ruthless with their every day work and sometimes fail to connect copper properly, or leave open copper touching conductors that increases noise... etc.. etc..
 
Try setting the modem to sync only with G.DMT modulation in the DG Team firmware, it's possible that you've been switched over to ADSL2+ equipment that dynamically determines the best sync rate on your line unlike ADSL(G.DMT) that tries to sync at a set speed.

Edit: I see that you say your exchange is now 10Mb enabled that means they've moved you over to ADSL2+ equipment.
 
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Yes, now the fail part of this situation is.

1) I have already tried unplugging all other related hardware in the house, except perhaps Fridges and such. Maybe wireless telephone could be affecting.

2) Yes they have changed the exchange to 10Mb exchange. However, I cannot seem to get my line to sync at ADSL2+. It still syncs at G.dmt which is strange. The only thing I have found on this is that the DSLAM that i connect to isn't ADSL2+ enabled yet ? Could that be ?
 
Let me further explain this situation. When my line was installed I had cable problems within the house because the router sits in the study which is far away from the telephone port.

What I had telkom do, is run another cable (THICK BLACK ONE) from the pole outside to the study directly, and the router plugs into that. Therefore I have the telephones and stuff on a seperate cable although the same number.

I was thinking about getting them to come and re-run that black cable from the pole as a start.
 
phatboy said:
Let me further explain this situation. When my line was installed I had cable problems within the house because the router sits in the study which is far away from the telephone port.

What I had telkom do, is run another cable (THICK BLACK ONE) from the pole outside to the study directly, and the router plugs into that. Therefore I have the telephones and stuff on a seperate cable although the same number.

I was thinking about getting them to come and re-run that black cable from the pole as a start.
Click to expand...

Did you try connecting the router using your telephone ports on the other side of the house to see if it is any better? If it is way better then it's the cable from the pole which came lose or something is touching it.

If it does work better can't you connect to it from the study using wireless N?
 
Come to think of it. I did test the theory, i connected it on the other cable. no it made no difference, so thats no the issue.

I cannot understand the problem, it can surely only be a problem outside of my house that telkom will have to fix, or its a router chipset issue as mentioned earlier to do with the exchange and the dynamic sync speeds. but if that was the case then I should possibly be syncing at higher speeds, but im still on G.dmt and im getting worse speeds then i was before the 10mbps exchange upgrade
 
phatboy said:
Come to think of it. I did test the theory, i connected it on the other cable. no it made no difference, so thats no the issue.

I cannot understand the problem, it can surely only be a problem outside of my house that telkom will have to fix, or its a router chipset issue as mentioned earlier to do with the exchange and the dynamic sync speeds. but if that was the case then I should possibly be syncing at higher speeds, but im still on G.dmt and im getting worse speeds then i was before the 10mbps exchange upgrade
Click to expand...

If you on G.dmt it may just mean your dslam doesnt support Adsl2+ and the exchange does that is what happened with me. My exchange is adsl 2+ yet dslam is not.

Do you have any friend with a TP-Link W8960N router?
http://www.dbg.co.za/product_info.php?cPath=1_55_57&products_id=383

It is either the cable to the dslam or dslam itself or the cable to exchange or exchange itself. Some people have mentioned that a failed dslam card had to be replaced to get their line working again.
 
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what a load of crap. how do i get them to fix my dslam so i get 10meg, or merely fix my line speed so i get 4096k again ?

Drive into it perhaps ?
 
phatboy said:
what a load of crap. how do i get them to fix my dslam so i get 10meg, or merely fix my line speed so i get 4096k again ?

Drive into it perhaps ?
Click to expand...

as long as you don't damage it too much that they won't even try fix it then you got no internet.
 
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