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84 posts

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Topic # 23600 3-Jul-2008 18:53
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Anyone got anyidea why these sync rates are so different? I don't know much about noise margins etc so maybe someone could look at this and offer an opinion. My limited understanding was a higher noise margin was better? and also look at the difference in power output.

This is the same modem on 2 different lines, 1st pair and 2nd pair. One to Orcon and one to xnet.

Mainline


second line

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  Reply # 142696 3-Jul-2008 19:22
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Jekkyl: My limited understanding was a higher noise margin was better?

Noise Margin is usually better at lower sync. rates.

Jekkyl: This is the same modem on 2 different lines, 1st pair and 2nd pair. One to Orcon and one to xnet.

Presumably the Orcon line is via their LLU network?  This would probably account for the difference.

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  Reply # 142700 3-Jul-2008 19:29
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I would say you have water in one pair, or the port at the exchange is damaged, or one of the pairs is still hooked up to an alarm or bad extension wiring.  Or someone installed under-floor insulation and did not look what he is doing with the staple gun...




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  Reply # 143875 7-Jul-2008 15:54
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Judging by the data you provided, you're using a Dynalink RTA1320 (or similiar Dynalink modem). If you are, download v8 (not v9, it won't support the modem) of DSL-Modem Tool from http://dmt.mhilfe.de/
Run the tool on both lines and compare the graph output. I find it gives a much clearer picture of the state of the line than the data output on the modem webpage.



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  Reply # 143949 7-Jul-2008 18:17
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Yea already used DMT to adjust my line noise and it made an improvement in speed but still quite a difference in the lines.

I didn't change the noise margin back for mainline so the SNR is pretty low but speed is even faster.

Not really sure how to read the graphs they look awfully similar thou.....except for the output power

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Master Geek
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  Reply # 152842 30-Jul-2008 22:37
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Looking for any more information on this. 8k sync rate compared to 12-15k is a really huge difference. Sure the higher one was on Orcons LLU network but the Glenfield exchange was upgraded to adsl2 so I would of thought I would get similar rates as i'm using the same lines just the port/gear at the exchange is different?.

I had a line test done and they cannot see any significant problems so they won't change me back from the 2nd pair to the 1st pair(the one that was with orcon and the high speeds). Could this just be a case of Orcons gear being that much better or could the line really show that much difference in Sync rate and have some problem that wouldnt show up on a line test?.


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  Reply # 152856 30-Jul-2008 23:27
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Orcon has their equipment setup differently, for example they have no interleaving on the upstream data and they have a faster upstream bit rate. Long story, but it makes your download faster at the expense of possible lost data (which your computer has to request/send again). Note that a small SNR (or noise margin) is bad, and on your Orcon line it seems to be too low. Also on the graphs your line speed is comparable, not as bad as in the modem status screen shots, so possibly the line was improved when testing was done or your exchange has gone through a commissioning phase which resulted in your port (and others) being adjusted for better performance.

You should check your modem status again to see what speed it connects at. As for line tests, anything above about 4Mbps would probably get classified as "no significant problem". It's a consumer grade connection to the exchange. Sure it does not make you happy, but that is the reality. In South Africa they are still trialling 4Mbps while customers pay more than what we do...




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  Reply # 152864 30-Jul-2008 23:58
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The 1.1 noise margin was just a test I adjusted on the modem to see how fast it would go. With them both sitting at around 6db snr the actually line rate is around 3-4k diff. I also know on the orcon connection I got d/l speeds of up to 1300kB, this what not always the case but I know it did get to that speed, the current connection gets no where near that speed ever.

Oh and anything over 1.5Mbps they don't really care about.

What I was wanting to know I guess was if anyone else gets better syncs/speeds in Glenfield who is not on orcon, trying to work out if changing the pairs back(even if I have to pay if its possible) will make any difference or if it's going to be a telecom exchange issue and not worth the effort.

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  Reply # 153103 31-Jul-2008 19:20
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It looks like Orcon is using a non-standard ADSL2+ profile.  See comment just before "installation issues": http://en.wikipedia.org/wiki/Adsl




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