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Author Topic: 21CN and very low SNRM  (Read 1413 times)


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21CN and very low SNRM
« on: July 07, 2011, 05:00:55 PM »

I was switched over some months ago to 21CN, and as I'm nearly 4Km from the exchange I did not have high hopes of improved synch speed.

Well, to my very pleasant surprise, I was wrong.

Using my DG834GT and DGTeam firmware, I have tweaked my synch speed up to 5.5Mb/s. Prior to 21CN it was around 3.5Mb/s

The SNRM is around 3dB or less, and right now Routerstats shows 2.1dB. But the exchange end seems happy enough.

About once a week, bad weather will cause a resynch, and in a week it will typically notch up around 500,000 CRC errors.

But download speeds are great, and web access seems unaffected by CRC errors.

Have other 21CN users had similar results?


  • Content Team
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Re: 21CN and very low SNRM
« Reply #1 on: July 07, 2011, 11:42:58 PM »

Hi Pintosal,

Most of the horribly long lines I monitor seem more stable and marginally faster when on 21CN provided they are left on ADSL 1 using 2Wire 2700HGV modems which contain an Infineon chip to match the new Infineon DSLAM.

However I believe RP has observed less stable connections.

We both note that the instantaneous (at re-sync time) IP profile adjustment to 88.125% of the Sync speed is usually a benefit.

Kind regards,


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  • Over the Rainbow Bridge
    • The ELRepo Project
Re: 21CN and very low SNRM
« Reply #2 on: July 08, 2011, 07:30:03 PM »

I am connected via 21CN equipment and, although I have nothing like as long a line as yourself or those that Walter is monitoring, I have far better stability by connecting via the original ADSL 1 modulation (G.Dmt).

As my downstream throughput is around 3 Mbps, I have nothing to gain by using any other form of modulation -- just a loss of stability, if G.Dmt is not used.
:cat:  100% Linux and, previously, Unix. Co-founder of the ELRepo Project.

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