Then that's what OP must be referring to in that quote, not the SNRM.

In reply to a post by meditator:

I seem to recall that +6dB is a doubling of LEVEL but +3dB is a doubling of POWER. So, the values you need to enter might depend on whether the router works with voltage levels or instead with power levels.

Yes, there are 2 ways of measuring the ratio of the actual physical quantity before taking logs; the power ratio (double = 3dB) or the amplitude ratio (double = 6dB). I was assuming the former. It may be that we should consider the latter, in which case a square root should be applied to my formulae, thus:

So enter the percentage as SQRT[10^((desired NM -6)/10)] *100.

To have a 12 dB NM when the DLM has set a Target NM of 6 dB enter:
SQRT[10^0.6 ]* 100 = 200%

To have a 15 dB NM when the DLM has set a Target NM of 6 dB enter:
SQRT[10^0.9] * 100 = 282%

In either case, that Australian forum & the usual suspect: http://www.kitz.co.uk/routers/dg834GT_targetsnr.htm do not agree with either and do not involve logs at all, which is strange considering that the dB is a logarithmic unit. They exhibit a purely linear relation:
Percentage = 16.7 * (desired NM -6) + 100

But what if your starting point is 12dB SNR? Using XRay's formula, if I'm starting from 12dB and I'm wanting 15dB, the decimal value you seem to need to enter is 200, ie. 10 to the power of 0.3. Is this correct, XRay?

Yes, I was using the normal Target NM of 6dB in my examples, believing that, as you were tweaking NMs, you would know this fact . I did say " when the DLM has set a Target NM of 6 dB".

However you can't start on this exercise until you have ascertained the Target NM awarded you immediately after the the last re-sync, as we have both suggested.

Hmm, between you, you can't seem to agree. This has left me rather confused.

I came across a printout I'd made about a year ago of the kitz table when I was sorting some papers last night, and kitz's figures are the same as the ones quoted on that australian forum, and the same as I used.

I think you must be right, Roberto, because the resultant dB figures I was getting agreed neither with the starting point of 6dB assumed in the kitz table nor with the starting point being my then snapshot SNR.

Given that, despite all the trouble, I've actually got the SNR I was aiming for, namely 15dB, I think for the present I'll just leave things as they are. The DSLAM seems to be happy with that. But if, over some time, things slip back I'll refresh my memory as to what to do (the Roberto approach) by coming back to this thread.

In reply to a post by meditator:

Hmm, between you, you can't seem to agree.

As it happens, Roberto's figures mainly agree with my 1st formula given here: http://forums.thinkbroadband.com/dslrouter/t/4192227... , but I'm beginning to have doubts about that. Neither of us agree with the Kitz linear table.

In reply to a post by meditator:

I think you must be right, Roberto, because the resultant dB figures I was getting agreed neither with the starting point of 6dB assumed in the kitz table nor with the starting point being my then snapshot SNR.

The starting point is never the instantaneous snapshot NM, as we always keep telling you and it is a waste of time even considering it as such. It is always the Target NM set at the previous re-sync. Kitz does not assume a starting point of 6dB or anything else for the matter; he always works on the change or delta from the Target NM.