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    Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

    This is a discussion on Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102 within the Technical discussion forums, part of the Broadband Technical Help category; Hi, I've been trying to improve our ADSL speed and have recorded some of the results below. Some quick conclusions ...

    1. #1
      Zander's Avatar
      Zander is offline Sky User Member
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      Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

      Hi,

      I've been trying to improve our ADSL speed and have recorded some of the results below. Some quick conclusions :-


      • ADSL filters, faceplates and cables can improve your ASDL connection stats a bit, but perhaps not your connection speeds so easily.
      • The SR102 seems to have significantly better noise-margin than the Sagem 2504n, though line-attenuation is about the same, and didn't improve download speed.
      • Solwise and Austin Taylor faceplates seem no better than the Sky ADSL filter plugged into the master "test" socket. They may be more appropriate if you have phone extensions in your house.
      • The "Sky SR102" seems to be a re-branded Sagem, with disappointingly identical functionality - just glossier web interface, slightly faster startup - and VDSL support. No QoS or bandwidth control. The wifi performance seems about the same as the old Sagem router.
      • The SR102's ADSL wire seems significantly worse than the old Sagem ASDL wire - as far as noise-margin.


      I'm more used to 10-15Mbs download in London, but am getting more like 3Mbs in rural Leicestershire. After realising that my cheap Tenda W311R+ wifi router was interfering with my ADSL signal, I've been reading a few tips around about ADSL faceplates, cabling etc. I also thought to buy an SR102 off Ebay in case a newer router helped.

      During my initial experiments removing the Tenda router and adjusting my connections seemed to increase my Sagem's downlink to around 4 or 5Mbps, but I haven't been able to replicate that since I'm hoping there's an element of line-tuning / DLM that may get me back to that range.

      Here is the Sagem 2504n vs Sky SR102, using the best combination I could make - a 1m ASDL cable from Amazon, the Sky ADSL filter and a new 4-way power chord from Wilko.


      Downstream Upstream
      Router Line Attenuation Noise Margin Speed kbps Line Attenuation Noise Margin Speed kbps
      Sagem 2504n 55 9.7 3071 33.3 8.7 797
      Sky SR102 53.5 14.6 3071 33.4 8.8 797


      Seems like quite a significant improvement in downstream-stats, but no improvement in speed

      Here are some other experiments I've been doing with the SR102 and other elements - ADSL cables, filters and power cords. The upstream stats are about the same for all of them, so I've just put the downstream stats.



      Router ASDL Filter ASDL wire Line Attenuation Noise Margin Speed kbps
      Sagem 2504n Sky filter 1m 55 9.7 3071
      Sky SR102 Sky filter 1m 53.5 or 54 14.6 3071
      Sky SR102 Austin Taylor faceplate 1m 54 13.9 3071
      Sky SR102 Solwise faceplate 1m 54 14.4 3071
      Sky SR102 Sky filter Old Sagem cable 54 14.4 3071
      Sky SR102 Sky filter New SR102 cable 54.5 13.2 3071
      Sky SR102 Sky filter 0.3m 54 13.8 3071


      I've tried a bunch of other elements too, like :-



      • 0.3m and 5m ADSL cables from Amazon - both had worse attenuation/noise-margin than the 1m ADSL cable.
      • Extension cables - these varied a lot, but this 5m extension worked best (with a short ADSL cable). Using this 5m telephone extension + short ASDL extension was better than using a long ASDL extension I bought.
      • Other ADSL filters - the new Sky ones seem to work fine, though not greatly better than the old ones I had.
      • Power extension cables - one old multi-way power block seemed to significantly affect noise margin.


      It seems that even moving the router around the room by a few cm, and adjusting cable positions can take noise-margin from the best I got of 14.6 dB down to under 10 dB .. and back .. so quite a sensitive measure.

      Now, my only options to improve are to hope for DLM adjustments (none so far), try a different supplier (BT?), or perhaps a Billion router and make more of that potentially improved noise-margin?


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    3. #2
      gymno's Avatar
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      Re: Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

      Quote Originally Posted by Zander View Post
      It seems that even moving the router around the room by a few cm, and adjusting cable positions can take noise-margin from the best I got of 14.6 dB down to under 10 dB .. and back .. so quite a sensitive measure.
      That should have no effect on the noise margin whatsoever.
      Are you sure the margin isn't up & down anyway, regardless of router position?

    4. #3
      Zander's Avatar
      Zander is offline Sky User Member
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      Re: Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

      Quote Originally Posted by gymno View Post
      That should have no effect on the noise margin whatsoever.
      Are you sure the margin isn't up & down anyway, regardless of router position?
      Hi,

      I've watched the stats closely and carefully - they're pretty steady generally, but I've seen that while I move the router the noise-margin can change quite a bit.

      I put it down to a few possibilities like cables being twisted/looped-up, power cable proximity to the ADSL wire etc .. all potentially causing some kind of EM interference.

      For example, right now I've tried to keep the ADSL & telephone cables apart from any power cables and seem to be getting higher noise-margin than average. I'm using a telephone/adsl extension and power extension both of which have a bit of excess length in them which can result in looping and overlap of the wires.

    5. #4
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      Re: Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

      There's definitely something going on internally.
      It's a case of eradicating it by trial & error.

      I notice in your (quite excellent) charts that the margin is significantly lower with the sagem than with the SR102.

      The sagem uses an external PSU, whereas the SR102's is internal...

    6. #5
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      Re: Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

      Good point about the power supplies.

      Certainly the most reliable way I can get the SR102 to have its best/highest noise-margin (14.5 dB) is if it is "alone" and spaced out in the room, with power and ADSL cables stretching away and ideally in opposite directions. I've not tried moving the Sagem around so much, but believe its consistently always "bad" compared to the SR102.

      I'm going to talk to Sky later to see if these increased noise margins might give them room adjust the connection speed higher.

    7. #6
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      Re: Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

      If you do find a sweet spot & give sky a call, then yes, DLM will give you a better connection.

      Personally though, i'd be aiming to rid myself of whatever's causing the interference.
      IE: ADSL extension, phone extension, mains extension, mains socket, nearby device etc.

      You can't beat peace of mind.

    8. #7
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      Re: Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

      Quote Originally Posted by Zander View Post
      Hi,

      I've been trying to improve our ADSL speed and have recorded some of the results below. Some quick conclusions :-


      • ADSL filters, faceplates and cables can improve your ASDL connection stats a bit, but perhaps not your connection speeds so easily.
      • The SR102 seems to have significantly better noise-margin than the Sagem 2504n, though line-attenuation is about the same, and didn't improve download speed.
      • Solwise and Austin Taylor faceplates seem no better than the Sky ADSL filter plugged into the master "test" socket. They may be more appropriate if you have phone extensions in your house.
      • The "Sky SR102" seems to be a re-branded Sagem, with disappointingly identical functionality - just glossier web interface, slightly faster startup - and VDSL support. No QoS or bandwidth control. The wifi performance seems about the same as the old Sagem router.
      • The SR102's ADSL wire seems significantly worse than the old Sagem ASDL wire - as far as noise-margin.

      Your first point - Using quality filters and cables will improve your speed, but that will not be immediately apparent. You line speed is fixed at 3072/800 by DLM and you will not exceed these until the speed is lifted. This also answers your second point.

      With ADSL there is little difference between the old type filtered faceplate and a plug in filter if you do not have extensions.The latest vDSL plates are better however, as they contain superior filters. They are worth using even if you do not have extensions.

      The new Sky Hub is not a rebadged Sagem. It is built especially for Sky and contains 'Sky' branded components, as do the latest plug in micro filters.. As you say, its performance is not that much better than the 2504N and was a great disappointment to many of us who hoped for a far better product.

      There is little difference in the quality of the ADSL cables supplied with the Hub, although some have proved to be below standard for Fibre, they don't make much difference to ADSL.

      Now that you are sorted out call Sky and tell them you have made improvements to your wiring and would like your line reset, either manually or by DLM training which could give a better result. If they say they can't do anything for you, hang up and try again until you get someone who will listen. Not always easy with Sky Help, most of whom only want to read from a script.

      TomD


      Please note the views and recommendations in my posts are my own and in no way reflect the views of SkyUser.


      Useful Utilites

      https://www.nirsoft.net/utils/wifi_information_view.html/ TCPOptimiser /Test Socket

      Note - When downloading always select the Custom install or you will end up with stuff you don't want.





    9. #8
      Zander's Avatar
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      Re: Experiments in noise-margin dB etc + Sagem 2504n vs Sky SR102

      Hi,

      Thanks for your reply - I was just updating a new thread with my conclusions more concisely

      Indeed, phoning Sky's technical broadband support did the trick, and made the most of the apparent noise-margin improvements, almost doubling our download speed and holding steady at 3dB noise-margin

      In all my tests, the noise-margin was the most obviously affected outcome - and I presume that is what would in turn affect the eventual download speed from Sky. I didn't see much change between any of the faceplates or filters, but am interested in your vDSL faceplate idea - though am quite happy with our speed now, probably the best in this broadband-poor area. I guess there is a possibility that these faceplates may result in a more reliable noise-margin, if not such a high (but slightly variable) one.

      The SR102 certainly "looks" like the Sagem from its web interface and features, though I'm sure it could be different inside. Anyway, it certainly seems to have a 50% better noise-margin than our old Sagem, so worth the upgrade for that alone in our case

      Cheers,

      Alex

     

     

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