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Routers and SNR:  Last updated: 15th Sept 2011

This page documents my ADSL problems caused due to falling SNRM (Signal to Noise Ratio Margin) in the evening and my experiences with different routers.

Netgear DG834    2Wire 2700     Thomson Speedtouch 585     Router Statistics    Lower Target SNR

Some background:
My broadband connection is via a BT line which is mostly overhead and also shares some of the same telegraph poles as the overhead power supply (which is a bad thing!).
I had been on a basic fixed 512kbps package since my exchange was adsl enabled at the start of 2004. This had been working fine and my problems started when I decided to upgrade to an 'Up to 8mbs' ADSL MAX (adaptive package) in the summer of 2007.

My line stats are: Attenuation 50, Target SNR: 12db Sync: around 4200kbps BRAS Profile: 3500
If you are new to ADSL I've tried to explain these key broadband terms on my Understanding Broadband page.

when my line was initially upgraded to a MAX product my target SNR was the normal 6db and I sync'd at 5,200kbps.
After a summer storm, the router had a 'fit' which BT's equipment interpreted as a permanent line issue and raised my target SNR with the corresponding lowering of my sync!

Netgear DG834v2
My first router was a Netgear DG834v2 with the latest firmware - v 3.01.31(UK)

I noticed the SNR dropped in the evening when it started to get dark, and would eventually lose sync if I didn't turn off manually to save my BRAS (IP) Profile). As this was around 9pm it didn't cause too much of a problem. Turning the router on the next morning I would enjoy my normal sync and speeds.

But since the days have been drawing in as we move in to winter the SNR has been dropping earlier and earlier.
It is thought the extra 'noise' on the the line is from RF (radio frequency) interference generated from a variety of sources. Lighting, central heating, generators, pirate radio stations, etc. etc. It's not uncommon for a long rural BT line to suffer from this ADSL problem.

To ensure your internal wiring performs at it's best fit an ADSL Faceplate Filter:

BT iPlate
Broadband Accelerator

If I re-connect the next morning at my normal speed and continue to do so for around 3 days my profile (and speeds) would return to normal. This is the biggest issue for me - running slower in the evening wouldn't be so bad, but having to suffer reduced speeds for the next 3 to 5 days due to BT's profiling system really starts to hurt!

The SNR statistics are captured using RouterStats a useful and free application from www.vwlowen.co.uk This simple application lets you monitor and graph your SNR margin and connection speed, as well as other adsl statistics. With the latest version the current SNR value is also displayed in the System Tray icon so you can keep you eye on your SNRM as easliy as checking the time! The software also lets you run scripts or sounds an alarm if the SNRM drops too low etc.  Highly recommended!

After being as happy as I could that the source of noise was not from within my house I started to look at changing my router to see if it would improve things. NB. I had already 'optimised' my line for ADSL as much as I could see ADSL page. After a lot of broadband forum reading it became obvious that quite a few people rated routers from both 2Wire and Thomson.

2Wire 2700
Second router 2Wire 2700HG-B using SBC firmware v4.25.19

Seems to manage SNR well - but still losing synch in the evening for me.

The 2Wire 2700 router isn't easily available in the UK. BT supply it as their BT Business Hub - but it's locked to BT in an attempt to stop it being used with other providers. There are a few ways of getting round this - if you need to know how to unlock a 2Wire then an internet search will show you what's needed. I bought my 2Wire 2700HG-B second hand on eBay and had already been unlocked having been flashed with SBC firmware.

Interestingly this is the first router I've found where the documentation actually references 'long noisy lines'.
 

From the 2Wire Router guide:
"High performance integrated modem. 2Wire’s technology improves DSL1 performance, especially for
homes further away from the local exchange. It also minimizes common interference found when other
devices (such as dimmer switches or fluorescent lighting) are in contact with the DSL line."
 

Thomson Speedtouch 585v6
Running 6.2.29.2 firmware.

Fixed my adsl max problems - No more disconnections!

The Thomson Speedtouch 585v6 seems to have fixed my low SNR problems!
The router still shows the SNR dropping as the evening approaches (this graph was taken just after the clocks went back after the end of BST so the times are one hour later in relation to the Netgear graph above) which is a normal occurrence - but now seems to stay stable around 8 - 8.5db in the evening. I've been using the ST585 for a couple of weeks now and it hasn't lost sync once. I've monitored the SNRM up to around 11pm and it's still around 8.5db.

The ST585v6 from Thomson has proved to be the best router for coping with low SNR on my long and noisy BT line.

I'm connected to a Texas Instruments(TSTC) DSLAM in my exchange and it seems the chipset in the Speedtouch (TMMB/Broadcom)  is a compatible combination for me. So I suggest if you are having similar problems with loss of internet connection in the evenings don't give up but try a new modem!

Update: 29th March 2008 - Target SNR reduced manually

My internet connection is still much improved after switching to the Thomson Speedtouch 585 v6 router
Thanks to www.thinkbroadband.com I've also managed to have my target SNR lowered from 12db to 9db.
This has increased my line speed (sync) to around 4800kbps (from 4200 with my 12db target SNR) which gives me a stable 4000 IP Profile - and no more flip-flopping between IP Profiles!

Below is a graph of my current SNR monitored by RouterStats software (see link above).
From my new target SNR of  9db my SNR fluctuates by only a few dbs. Dropping by 2-2.5dbs in the evening transforming my ADSL MAX connection from my Netgear days.

See my ADSL page for tips to understand and improve your broadband connection: ADSL information

Update: 21st December 2008 - Target SNR reduced automatically

After seeing my connection run cleaner (less FEC/HEC/CRC errors) for a few weeks I was pleased to see on the 13th December I connected at 5504kbps around 1/2Mb faster than normal! Looking at my SNRM I found it was now 6db rather than my normal 9db - so BT's systems have automatically lowered my Target SNR to the default 6db.

Just for the record, I power my router off every evening and turn it back on first thing in the morning - so this shows that the Exchange equipment (DSLAM) does lower a Target SNR without seeing a continuous connection for 14 days or more as is often documented. The lowering of Target SNR is something of a 'black art' and the exact conditions are kept secret by BT unfortunately.

After running for 7 days syncing around 55xx my IP Profile(BRAS) increased to 4500.
It's normally thought IP Profile increases happen between 75 minutes up to 5 days but for this increase it took a full 7 days at the higher connection speed. My current SNRM still drops by 2 to 3db in the evening, which is normal - time will tell is my flaky line can maintain this speed - but for now I'm happy!

Update: 15th September 2011 Good internet speeds

Just to say I'm still doing well on my trusty Broadcom chipset Thomson ST585v6.
Attenuation showing as 51db, Target (default) SNRM 6db, connecting at  around 56xx - 58xx kbps
This means my IP Profile is usually 5000 changing to 4500 if I connect in the lower range.

Below is an up to date noise margin (SNR) graph from RouterStats for my broadband connection using the Speedtouch 585. This show things are running nice and smoothly connected with a 6db Target Noise Margin.

More on Target SNR here

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