I've discovered the way how to check upstream Hlog, upstream QLN and upstream SNR on D-Link DSL-2740B. Usually this modem shows only downstream Hlog and QLN. On typical Hlog graph there are only noises. I supoose the similar way works on other Broadcom-based modems.
1. telnet 192.168.1.1
2. adsl connection --diagmode
3. wait a few minutes
4. adsl info --linediag
First attachment is typical Hlog graph. Second attachment is Hlog graph with upstream attenuation.
Best regards
konrado5