My cab is a long way from the exchange and I'm quite a long way from the cab. Power back-out blows a very obvious whole in the lower frequencies and heavily effects my transmit speed. The bit loading reflects the PBO mask, which isn't a straight forward curve.
The power back-out masks are published somewhere, I can find them if need be, but they definitely effect users in the "long long" category as the power is backed out to avoid interference with ADSL on the long d-sides.
IIRC there are 5 different masks that are applied to long d-sides, and which mask is applied is dependant on the electrical length of the cabling from the cab to the exchange, the further it is the more the attenuation applied.
Or something like that
Edited by Lorian (Thu 07-Feb-13 08:43:02)