Sudden slow speed on stable BT Line

My line was running very stably at around 4 Mbits. In fact up till about 2 weeks ago the downstream speed was 4128 and there had been no router resync for nearly 3 months. Then it became unstable, speed slowed and I called BT. When the engineer arrived the problem had gone away.

Last weekend more issues but now the line is super stable, but the sync speed is consistently between 640 kbps and 704. I've got BT coming again on Friday but is this a line problem or a broadband issue?

These are my stats

ADSL Link Downstream Upstream
Connection Speed 640 kbps 448 kbps
Line Attenuation 51.0 db 29.0 db
Noise Margin 12.8 db 22.0 db

The DMT tool shows that only the low end of the spectrum is being used.

http://i859.photobucket.com/albums/ab152/rfsmith7/Ca...

Any ideas?

Post deleted by Deadbeat

Have you tried a different router?

The way everything suddenly drops off is a little odd. If I look at my router I get a gradual drop of in bit loading and then at the higher end occasional little blocks of tones that could carry data.

Could also be your main filter - a failed component has changed it the characteristics from a pure low pass. Or even the very front end of the modem part of the router - there is normally an inbuilt hi pass filter there too, maybe that has problems.

Try it without a filter in the socket and see. Also turn the router off for a couple of hours and then try it again.

I have an ADSL filtered faceplate. I've tried both connecting directly to the BT master socket behind that, and using my BT Home Hub 2 instead of the Netgear DG834GT router that I normally use. Same result every time - 640 kbps download speed.

That has ruled out everything at your end ...

Can you also get a Bit Loading graph from the BT Home Hub? Having two similar reports will be an easy demonstration that the fault is outside the property.

The bit-loading graph is coming from the DMT tool which doesn't connect to the BT Home hub. I'm pretty certain the problem is outside the house, but whether it's a physical line problem or a broadband configuration issue at the exchange is what I'm trying to establish.

Does the HH not give one? The BT Business Hub does provide me with a graph - not as pretty but enough to see what is happening.

Not as far as I am aware, though if you can tell me how I'll give it a try.

Sorry, don't know the HH, but can you access the diagnostics and work through?

There's no command-line interface on the HH so I don't believe you can get any diagnostics. Even the report on the bitmap for the Netgear has come from DMT rather than Netgear.

I'm satisfied the problem is outside my property so I'll see what BT have to say on Friday. I was just wanting to know if the symptoms of the problem were indicating a BT equipment/line fault or whether it was a broadband issue at the exchange.