My findings on the hi-speed cable:
Well to start with the initial 18dB declined and after 10 min was about 13dB at its lowest. I recon this is just the line conditions which the router seems particuarly sensitive too, it usual varies alot in the day and has previously fallen to 10dB.
What i've done is use the Voyager 105 modem, with both a standard cable, and hi-speed cable in three places - on my dedicated ADSL extension socket, on the front of the master adapter, and at the master test socket.
I then called up the line stats and watched what they did, and finally connected up and did a ADSLGuide speed test.
So, then, the extension socket:
Best sustained SNRM: 15.5dB with both cables. Qaul cable got a line rate of 479.3Kbps and the standard 476.9Kbps.
At the NTE5 ADSL adaptor best sustained SNRM was only 14.5 - 15dB. This was somewhat strange. Probably changing line conditions here rather than signal loss, as this was about 3/4 hour after the first benchmarking. Line rates were worse still at around the 360Kbps mark.
Finally at the test socket, best down SNRM was 16.5dB with line rates going up to 412Kbps and 393Kbps respectively.
My thoughts:
The hi-speed cable I was using was 2 metres. Whilst the standard cable seemed to match it for the most part, the standard cable is about 1 metre long. I have seen problems with ADSL and ordinary telephone extension leads, so those are the ideal scenarios for these cables - where a longer and quality connection lead is required and a flat cable can causes great signal loss. Also the cable seems to work much better on routers, sustaining a slightly better signal rate than that regular cables.