Up/Down stream Attenuation difference

Is it normal to have a big attenuation difference between the up and down streams?

My stats are:

Downstream attenuation: 51
Noise Margin: 5-10 (goes up and down quite a bit)

Upstream attenuation: 15.5
Noise Margin: 18 (very stable)

As you can see there's a huge difference, but why?

When my router syncs I always get the max upstream sync rate possible for my line, but of course terrible downstream sync rate (varies between 1 and 2mb).

Margin - yes it is quite normal for the downstream to vary especially day to night whilst upstream stays reasonably constant.

Attnuation - downstream is nearly always higher than upstrem but the differenc does appear to be greater than that I would normally see.

Overall there is nothing to say there is a fault on the line - just one with high attenuation and a lot of noise over which you may/maynot have any control.

If I did have control over it, would could I try to find out?

Apply physics. The upstream channels use lower frequencies than the downstream. Higher frequencies are more susceptible to loss. This is more obvious with ADSL Max than fixed rate because the extra bandwidth uses even higher frequencies.

Most of the things which cause attenuation are outside your property, the biggest single one being the length of the line.