BT speed estimates

Hi,

I'm just wondering if anyone can tell me how reliable the estimates for fibre speed from BT are?

I put in my telephone number and get "up to 37.5 down and 6 up", which I thought seemed a bit low as I'm less than 200m from cabinet.

I then put in the number of a business which is 2 doors down from me, result is "up to 71.9 down and 20 up"

Why would there be such a difference - from what I can tell both properties are fed from the same pole in a neighbour's garden, and the availibility checker shows we are both on the same cabinet?

what are you putting the number into ?

Hi Yarwell,

it was this one :-

https://www.btwholesale.com/pages/static/Community/B...

When you put your numbers in to that checker, what does it say for the the cabinet number of each one? it should say at the top of the listing something like this:

Telephone Number 1234567890 on Exchange SANDWICH is served by Cabinet 5

Chances are you are on a different cabinet, and it's not as close as you think.

Edit: As to how accurate it is, it's believed to take into account cross talk, which is interference from other lines, so should be pretty accurate. Most people find they exceed the estimate, but as the cab fills up, and interference increases speeds drop back closer to the estimate.

Some people, like myself never get anywhere near the estimate, mine is 57, but I'm currently getting 47, but was only 42 until recently. It very much depends on the quality of your line.

Edited by R0NSKI (Thu 16-May-13 20:24:20)

both tests give same cabinet number :-

Telephone Number **** on Exchange ***** is served by Cabinet 47

would crosstalk affect properties 10 metres from each other so differently?

Also, is it possible that my line (residential), and my neighbours (business), could account for the difference?

Hmm, strange, are you on overhead lines, if so do the phone lines go to the same telegraph pole?

I doubt very much it would make any difference being a business line, it's one of two things

1) Your line for some strange reason takes a long route back to the cabinet (not that unusual)
2) It's a database error, and you'll actually enjoy near full speeds.

Edited by R0NSKI (Thu 16-May-13 20:39:28)

Hi Ronski,

thanks for taking the time to answer -

as far as I can see there are no overhead lines anywhere in the area, and all the lines fed by the cabinet seem to be within a tightly constricted area (busy road on one side, canal on another)

I was just wondering how common these database errors were, -

currently I'm considering updating to fttc but there's a chance I'll be moving house before the end of the year, I would risk getting into an 18-month contract for 20mbps upload speeds but 6mbps upload would probably not be so worthwhile

(first world problems, I know )

When I started mapping our local cabinets, I found lots of what would appear to be errors, for example a cabinet one side of town supplying a very small percentage of properties in a postcode several miles away. In an area like ours with many cabinet close by I really can't see this being anything other than a database error. I've seen this many a time when searching for cabinets in other areas for people on the forums.

I've also seen many examples where somebody can't get FTTC, but other houses on the same cabinet can, after said person has contacted BT they magically become able to order FTTC.

When you consider just how vast the BT database must be, I have 1,318687 records in my database, each record is a different postcode (this data is from a leaked spreadsheet from 2011). It does not contain all postcodes though, as not all the country was included in it. Then imagine how many telephone lines are in each postcode, the total number must be vast, and all this data is added from old records over god knows how many years, that leaves a lot of room for errors, so it's not surprising they crop up from time to time.

I would suggest trying your neighbours telephone numbers if you know them, or their addresses in this checker, you only need house number and postcode (check on the Royal Mail website for the correct postcode) and see what their estimates are. If you enter just the postcode (in the one I linked to) you can select one address, see the results, click the browser back button, select the next and so on.

I think it's just an error.

In reply to a post by ampad:

I'm just wondering if anyone can tell me how reliable the estimates for fibre speed from BT are?

R0nski's given you the right answers. Here's my personal experience:

My current line is 400 metres, with an estimate of 55/18. It initially achieved 80/20, with maximum attainable speeds of 88/26 (reported by the modem). Over 18 months, the crosstalk has increased, and the modem now reports attainable speeds of 72/25.

I'm still actually sync'ed at 80/20 (the last resync was 6 months ago, when I could still get an 80Mbps downstream) but with a noise margin of only 3dB. I guess it'll drop one day.

In reply to a post by ampad:

would crosstalk affect properties 10 metres from each other so differently?

Crosstalk is a funny beast, and depends more on how close the copper pairs are within the cable - which ultimately depends on the manufacturing process - and which households actually take the service.

It means that there *could* be a dramatic difference on any two properties no matter the distance between them.

However, the effect is random and unpredictable - so BT's checker cannot take crosstalk into account to that extent for every individual line. Instead they know what is statistically the worst case effect for each distance, and apply that to every prediction/estimation.

So, if both your lines are the same length and made of the same material, the prediction ought to be the same too.

In reply to a post by ampad:

Also, is it possible that my line (residential), and my neighbours (business), could account for the difference?

Business/Residential wouldn't account for the difference, but some other aspect of the line certainly could. Perhaps one line uses an aluminium cable in the return to the cabinet. Or perhaps it returns a different route - both would affect the prediction.

As both lines go to the same pole, you'd think this was less likely, but it isn't impossible. The possibility of a database error is there, as mentioned by R0nski, but isn't a certainty either. You might just have to pay your money to find out.

In reply to a post by ampad:

currently I'm considering updating to fttc but there's a chance I'll be moving house before the end of the year, I would risk getting into an 18-month contract for 20mbps upload speeds but 6mbps upload would probably not be so worthwhile

We went with Plusnet's fibre-extra package on our old house, and later moved within contract. The fact we moved wasn't a problem - we just connected to fibre at the new property and stayed on the same contract. If we'd moved to a non-fibre area, we'd have been forced to drop to an ADSL package with them, but wouldn't have been penalised - though I have no idea if they work the same way now.

Plusnet also have a nice touch if you need to break out of the contract early - they don't charge you the full monthly price for the remaining period. Instead it is around £5-6 per month remaining (you can find the actual amount on their legal T+C page, I think.

In reply to a post by R0NSKI:

If you enter just the postcode (in the one I linked to) you can select one address, see the results, click the browser back button, select the next and so on.

Yup - this process works well, having acquired the postcodes from Royal Mail's postcode finder (using just street name and town).

I`m pretty close to the green cab but if your line goes round the houses or is just rubbish then you get what you can get. BT estimate 55Mb up and 18 Mb down, I sync at 44Mb and 12Mb. To be honest its plenty fast enough, for a fully connected household!