Acceptable range for SNR fluctuation + trace noise

  hatrickj 20:14 30 Oct 2007

My modem router statistics at times show cconsiderable SNR fluctuation, this afternoon and evening ranging from 15dB down to 3dB. Allowing for the usual suspects like street lights and electricals cutting in out, what would be considered an acceptable fluctuation range, 12dB as above or something else?

I understand that noise sources can be traced by the use of an analogue radio receiver off-tuned from any station. Is that fact? How is it done and what waveband and frequency has to be used?

  Dipso 21:21 30 Oct 2007

I would say a normal SNR fluctuation would be no more than 3db max any higher could indicate a problem with interference.

Are you on ADSL Max? What router do you use?

If you think you know the source of the problem e.g. a streetlamp you can use a MW radio to try and listen to find the interference, not sure of frequency, just tune around and see if you can pick anything up.

I use a tool which identifies the frequency of interference on my line (amongst other uses) but this is only compatible with certain routers. Here is a screenshot of a line (not mine) showing the frequencies of gaps at the bottom right click here If your router is compatible you could try it.

Have you removed the ring wire from your master socket if as this can act as a AM radio antenna?

  hatrickj 10:18 31 Oct 2007

ADSL Max Netgear DG834G. Problem seems to habe no absolute pattern but dips are more noticeable at night and even occur in the sleep hours. AFAICS the ring wire is not connected.

This morning had a massive dip from 14dB down to 8, but within the 2 minute recording interval it was back up to 13/14dB for c.12 minutes, from whence it has flat-lined at 13dB. I've never had that since making records ( from c. 25/10).

  Dipso 16:31 31 Oct 2007

The DG834G v1 and v2 are known to suffer from fluctuating noise margin reporting so it may not be an external problem afterall. Check out this post click here the Netgear is "on the list".

As I said in the link, in my case replacing with a different router solved the problem for me.

What do you use to record the noise margin? Have you tried click here

  Taff™ 17:21 31 Oct 2007


  hatrickj 17:23 31 Oct 2007

Actually mine is v3, different chipset I believe.

  Dipso 21:14 31 Oct 2007

So the router isn't too blame...back to the interference then, unfortunately though the DMT tool doesn't work with the DG834G.

  hatrickj 06:48 02 Nov 2007

I also suspect my hard wired extension. In the day both main ( incl. test) and extension sockets perform roughly equally. Come night both fall off with extension one falling more. Not only does the extension one fall off more, but the range between the spikes and troughs, often one following the other immediately, is far greater than that seen when using the master socket. This last phenomenon puzzles me. Cab a kind soul explain, as ignorantly I'd have expected one socket to produce a noise margin range of, say, 8db to 4dB and the other 6db to 2dB ( both ranges 4dB) and not for the latter to be 6db to minus 2dB. I'd also have expected the extension to have less margin in the day too.

Any educators around? :)

  Dipso 16:54 02 Nov 2007

If you are also seeing the "fall off" from the test socket then this confirms your hardwired extension isn't to blame.

Bump for "educators".

  hatrickj 17:32 02 Nov 2007

Sorry I did not make myself clear. There is naturally some fall off in the evening and night at the main socket, especially with a street light within 40ft but it is nowhere as much as that seen when using the extension, nor are the fluctuations as violent.

  mjdmjd46 10:52 09 Jun 2008

I am experiencing sudden SNR variations of 14 db at random times during te day. Typically I get 5-8 jumps of 14-15 dB (i.e. very much the same each time), rarely on Sundays. This causes my line to work with a 22 dB margin normally, to accomodate the period of "noise". Any suggestions? Mike

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