OK(ish) attenuation, terrible SNR

R

recre8

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Cape Town, WC
Hoping you guys can help me out here. They recently moved my line to a DSLAM/IMAX unit that they just built within the estate where I live. WebAfrica's control panel shows that the exchange is capable of 10Mbps, BUT according to my line stats, the highest "safe" speed is only 6144. I switched it to 6144 and it wasn't stable.

Now... my issue is that the actual white Telkom box is only about 500m away. Granted the cable might not, and probably doesn't, run in a straight line to the box, but the estate is only 4km big. Herewith the stats as reported by the WebAfrica control panel (my router concurs)

Downstream Speed: 5023 kbps
Upstream Speed: 507 kbps
Downstream SNR: 6.8 dB
Upstream SNR: 9 dB
Downstream attenuation: 39 dB
Upstream attenuation 46 dB

Using this tool: http://fremnet.net/article/216/adsl-theoretical-speed-calculator

The calculated distance from the DSLAM is 2.8km and I should be able to achieve a sync rate of up to 12380 kbps.

Why am I having such a terrible SNR? What can I do about it?
 
There is something terribly wrong with your upstream attenuation!
The upstream line attenuation with ADSL should usually be roughly 1/2 the downstream line attenuation value.

I'd suggest that you remove your telephone & filters completely, leaving only the ADSL modem plugged in. If that doesn't fix the high line attenuation values. Also try and get the cable going from the modem to the wall socket away from other electrical equipment that could interfere with the signal.

If you cannot get your upstream line attenuation fixed by removing the filter & other telephonic devices, then you should call Telkom to fix it.
Perhaps just log in on your own ADSL modem and check if the stats match that of the WebAfrica console that you used.

Given that your downstream line attenuation is also fairly high, you may not be able to get a stable connection faster than 4Mbps.
 
Pada said:
There is something terribly wrong with your upstream attenuation!
The upstream line attenuation with ADSL should usually be roughly 1/2 the downstream line attenuation value.

I'd suggest that you remove your telephone & filters completely, leaving only the ADSL modem plugged in. If that doesn't fix the high line attenuation values. Also try and get the cable going from the modem to the wall socket away from other electrical equipment that could interfere with the signal.

If you cannot get your upstream line attenuation fixed by removing the filter & other telephonic devices, then you should call Telkom to fix it.
Perhaps just log in on your own ADSL modem and check if the stats match that of the WebAfrica console that you used.

Given that your downstream line attenuation is also fairly high, you may not be able to get a stable connection faster than 4Mbps.
Click to expand...

The line is actually only plugged into the DSL router. I have no other equipment (telephone etc.). I'll check the stats tonight. The router lost sync again, and my RedAfrica account doesn't like being dialled quickly in succession, so the router is now stuck on "Authentication Fail" and won't retry. So no access from work to home.
 
Last edited:
Had the same problem last month - SNR was below 6db

There was also audible noise on my landline

Tried everything to no avail, in the end Telkom came to my house and replaced the wire from the outside of the house to the inside wall socket

The wire was all frayed up and exposed copper was scratching against the conduit piping - now my SNR is at a steady 26db and very stable connection

Only posting this, so it can help with the problem solving process
 
Dion Disco said:
Had the same problem last month - SNR was below 6db

There was also audible noise on my landline

Tried everything to no avail, in the end Telkom came to my house and replaced the wire from the outside of the house to the inside wall socket

The wire was all frayed up and exposed copper was scratching against the conduit piping - now my SNR is at a steady 26db and very stable connection

Only posting this, so it can help with the problem solving process
Click to expand...

Thanks for the info. I'm considering redoing the cabling inside the house. But yes, it sounds like I might need to ask Telkom to come and have a look. Something just doesn't seem right.

Any idea where I can buy telephone cable? Some place like Scoop maybe?
 
Sorted. This weekend my connection kept dropping, so I decided to trace the telephone line. Telkom used these strange crimping connectors to splice two sections of telephone cable together. The one connector was missing the metal piece and effectively my DSL has been running on only one wire the entire time. I don't have a phone plugged in, so I never noticed it.

My new stats after fixing the wire:

Downstream Speed: 6144 kbps
Upstream Speed: 635 kbps
Downstream SNR: 24.8 dB
Upstream SNR: 17.5 dB
Downstream attenuation: 22 dB
Upstream attenuation 11.8 dB

Old stats from the single-wire DSL for comparison:
Downstream Speed: 5023 kbps
Upstream Speed: 507 kbps
Downstream SNR: 6.8 dB
Upstream SNR: 9 dB
Downstream attenuation: 39 dB
Upstream attenuation 46 dB

I logged a ticket with WebAfrica, to reset the profile on my line, since I can only select up to 6144, so hopefully later this week I will be on a full 10Mbps. The above stats indicate it should be able to sync without issues at 10Mbps?
 
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