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Netgear DGN 2200M router - strange changes to U/S noise margins?

dvvrue95
Grafter
Posts: 132
Registered: 17-08-2007

Netgear DGN 2200M router - strange changes to U/S noise margins?

Good Morning folks,
I recently replaced a aging BT Voyager 2110 router with a DGN 2200M. After the usual hiccups with ADSL2 settling down, BT vs PN profile changes etc the new router appears to be performing  better than the Voyager. I am on a long line approx 6.5km from BT exchange in a very rural area. So I am pleased at my PN profile of 1.3M which has been stable for 14 days
now.
However having managed to set up the full version of RouterStats to monitor the Netgear router I have discovered that (at what appears to be random times) the U/S noise margin
which is usually stable at around 4db spikes upwards to 6500db  sync speed is 664kbps  Cheesy. I dont appear to lose router sync and the D/S noise margin remains stable at 2.5db with a sync speed of 1490kbps. I have removed all extraneous sources of  "obvious" noise like pc power etc but the condition remains.
I'm still trying to figure out how to cut and paste RouterStats results so will post another message hopefully with some graphs. Meanwhile here are the routers current stats.

System Up Time 16 days 21:11:28
Port Status TxPkts RxPkts Collisions Tx B/s Rx B/s Up Time
WAN pppoa 1332240 2239682 0 0 0 14 days 19:11:58
WWAN PPP
LAN1 Link Down -- -- -- -- -- --
LAN2 Link Down --
LAN3 Link Down --
LAN4 Link Down --
WLAN 300M 2372088 1412282 0 7745 531 4 days 12:06:23
ADSL Link Downstream Upstream
Connection Speed 1490 kbps 664 kbps
Line Attenuation 63.5 db 38.6 db
Noise Margin 2.3 db 4.1 db
any ideas Ian
5 REPLIES
Plusnet Help Team
Plusnet Help Team
Posts: 13,247
Thanks: 195
Fixes: 61
Registered: 27-04-2007

Re: Netgear DGN 2200M router - strange changes to U/S noise margins?

It's unusual to see such a severe spike like that, without wanting to stick my neck out too far I would suspect some form of external interference, be that radio or electrical that could be causing that to happen.
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 Adam Walker
 Plusnet Help Team
dvvrue95
Grafter
Posts: 132
Registered: 17-08-2007

Re: Netgear DGN 2200M router - strange changes to U/S noise margins?

Afternoon folks,
Ok so have managed to attach some TX noise margin graphs from a couple of days ago.
I will try running RouterStats again later today to see if issue still there or any pattern.
Thinking of trying a ferrite core on LV power supply to router?
cheers, Ian
Community Veteran
Posts: 5,092
Thanks: 453
Fixes: 17
Registered: 10-06-2010

Re: Netgear DGN 2200M router - strange changes to U/S noise margins?

If the noise margin increases, that means either:
all noise ceases for an instant (well, that or an enormous increase in the signal, which doesn't seem any more likely)
or
it's a garbage reading and can be ignored.
Another possibility is the router isn't reporting a negative value properly, and displays some large number instead.
Community Veteran
Posts: 19,100
Thanks: 437
Fixes: 21
Registered: 31-08-2007

Re: Netgear DGN 2200M router - strange changes to U/S noise margins?

Well ejs has said more or less what I was thinking before I read his post.
Community Veteran
Posts: 6,313
Thanks: 86
Fixes: 3
Registered: 08-01-2008

Re: Netgear DGN 2200M router - strange changes to U/S noise margins?

Yes, the numbers make sense, a 16 bit register can hold a positive value up to 65536 (Binary 1111111111111111), since a register doesn't work in a 'negative' sense (all the bits must be 0 or 1) the range from 32769 to 65536 is used for negative values and the register is marked as a signed integer.  If the software is not correctly seeing the register as signed then a small negative value will be seen as a value close to  65536.
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