sync rate better on extension

Why would my sync rate at my master socket test socket be lower than on my extension in the bedroom?
With my router connected to my BT installed extension in my bedroom i get a data rate of 1664 Kbps and when i connect it to the test socket I get a data rate of 1330 Kbps.
I am in the middle of logging sync rates and through put tests for my ISP to diagnose why my broadband is unstable and found this to be a weird result.

Any Ideas?

Dodgy wiring?

Does the extension stop working when the router is connected to the test socket? ("Yes" would be good).

Yes it does stop working the extension is connected to the face plate

In reply to a post by spearedrino:

Yes it does stop working the extension is connected to the face plate

What's the sync rate when you connect to the faceplate?

Thats a very good question, why didnt i think of that!

I will try that......

Sync rate at faceplate is the same as connecting to the test socket 1312 Kbps

Edited by spearedrino (Mon 01-Nov-10 20:06:54)

Where does the BT line enter the property? Is it directly into the master socket or elsewhere?

Any other extensions other than the one mentioned?

Edited by deleted (Mon 01-Nov-10 20:35:48)

Line enters via window frame into a junction then down to the master socket. There is a BT installed extension to the bedroom upstairs and a plug in estension to the sky box with one phone also connected to the master socket (double connecter with the sky extension). I have just reconnected the router to the extension upstairs and it is showing 1728 Kbps now

Odd innit. Are you using a filter in the extension socket, and the same filter when connecting to the test socket?

Maybe a source of RF noise close to the master socket, that is being picked up by the modem lead

Sky box?