Very low SNR, how to convince BT to check?

Hi, I've had BT Infinity for a couple of years now.. Only getting 35 Mbps at the moment which I've always thought strange because I'm on a residential street not far from the exchange, so I guess it must be the quality of the copper between me and the cabinet. I'm sure I should be able to get the full 70 Mbps

I'm now using a Draytek 2860 which allows me to check line stats and I'm seeing 6 dB SNR which I believe is borderline.

Does anyone have any method for convincing BT to commit an engineer to come out and test the cable between my property and the cabinet?

6dB noise margin is the standard value on FTTC. As you are close to the exchange it's possible you used to get nearly 24Mbps on ADSL2+ with a high noise margin, but FTTC and ADSL2+ don't work the same way in that respect.

Please could you also supply the rest of the stats, the exchange name, and your cabinet number.

The estimates from this checker would be useful. (Just copy and paste, we don't need the pretty layout using a screen print). Also on the line above the table, is the cabinet number what you expect?

Could you also run the BT Wholesale Performance Test, ignoring all the red instructions for now, and at the bottom of the results page click the Further diagnostics button. Give it your phone number when asked, then copy and paste the contents of both the down boxes of results . We don't need the fancy graphics.

Edited by RobertoS (Sat 26-Sep-15 23:54:24)

Roberto, thanks very much for the advice. Here's my detail:

From the "Availability Checker"

Telephone Number 0118xxxxxx on Exchange CAVERSHAM is served by Cabinet 6
Featured Products

Downstream Line Rate(Mbps)
Upstream Line Rate(Mbps)
Downstream Range(Mbps)
Availability Date

High Low High Low
FTTC Range A (Clean) 35 26.8 7.5 5.5 -- Available
FTTC Range B (Impacted) 28.1 15 7.2 3.3 -- Available
WBC ADSL 2+ Up to 12 -- 7 to 17 Available
WBC ADSL 2+ Annex M Up to 12 Up to 1 7 to 17 Available
ADSL Max Up to 6.5 -- 5.5 to 8 Available
WBC Fixed Rate 2 -- -- Available
Fixed Rate 2 -- -- Available
Other Offerings
FTTP on Demand 330 30 -- Available
Fibre Multicast -- -- -- Available
Copper Multicast -- -- -- Available

From the BT Wholesale Broadband Performance Test:

Download Speed (Mbps): 33.09
Upload Speed (Mbps): 5.68
Ping Latency (ms): 25.88

From my router:

DSL Connected : Down Stream : 34998Kbps / Up Stream : 6220Kbps
Running Mode: 17A
Actual Rate: 34998/6220, Attainable: 37229/6250
Path Mode: Fast
Interleave Depth: 1
Actual PSD: 6.9 dB (Downstream) / 11.2 dB (Upstream)
SNR Margin: 7 dB (Downstream) / 6 dB (Upstream)
Attenuation: 25 dB (Downstream) / 29 dB (Upstream)
CRC: 181 (Downstream) / 14627 (Upstream)
FECS: 0 (Downstream) / 257709 (Upstream)
ES: 52 (Downstream) / 12573 (Upstream)
UAS: 25 (Downstream) / 317 (Upstream)
...

So your line is running right at the top of the BT estimations and BT would never consider sending an engineer unless your sync was to drop below 26000Kb/s or 26Mb/s.

Fibre (FTTC) is based on the distance from the cabinet and not the exchange and uses significantly higher frequencies that ADSL meaning that they decline in quality much quicker the further they have to travel from the cabinet.

The SNR of 6db is standard for fibre connections and will only ever be higher if a person is so close to the cab that they are able to achieve higher speeds than the package they purchase can allow.

Cabinet 6 is at https://www.google.co.uk/maps/@51.4713133,-0.9781026...

So the next question is how far is the original poster from that location.

Does that matter... BT Wholesale and Openreach have final say and that will be that the estimates are XY&Z

Yes it does matter, because if they are at about the right distance for the attenuation, then safe to say nothing more to be got from the line.

The title of this post is "How to convince BT to check" and based on the BT's own estimates, they certainly wouldn't consider checking anything... you know that as well as I do!

The only thing that can come from bringing up distances and attenuation figures is frustrations as and example they may be much closer to the cab but there line may route via another dimension (exaggeration)

So explaining the reality of being say 700m from a cabinet to an end user who otherwise may think that much higher speeds are possible at that distance is not worth doing?

not really as it could open up a whole can of worms!

Say you said that too me with 55meg but then you tell me I'm 200-250 metres from the cab so should get close to full 76Mbps, but then turns out you measured my line going an alternative route 350 metres, thats still then leave's me looking up speeds vs distance and finding I should still get 70-80meg...

then it opens up the reasons to why my line is under performing?

I know the above might be a bit long winded but it has a point.