Because ADSL2 (max 12Mbps) and ADSL2+ (24Mbps) operate at much
higher speeds, they are more prone to interference and noise on the
phone line than ADSL1. Unfortunately debugging ADSL2/2+
synchronisation and drop-out problems is very much an arcane art,
consisting of â€œtry thisâ€ until either the problem is resolved, everyone
runs out of ideas, or the user accepts that its as good as it gets.
The key indicators of ADSL2 performance are SNR Margin and Loop Attenuation, and you can find these in the bottom right corner of the Online Status page.
- Loop Attenuation can be used as a rough gauge of distance
from your telephone exchange (13.81 per kilometre), and so the lower
the better. See What ADSL2/2+ speed am I likely to get ?
(Signal to Noise Ratio) indicates how clearly your modem can hear the
ADSL signal over any background noise, and so the higher the
better. Note however that Telstra has no hard limits for either of
This is our list of Tips:
- Update your modem/routerâ€™s firmware. DrayTek have
supplied several â€œflavoursâ€ of each firmware version (see here) with
different modem code. The different "Modem Code"s indicate different
fine tuning settings of the ADSL2 parameters - so some will be better
and some worse on any individual phone line. ALL the modem codes on our download page
will work in Australia/New Zealand. Test each in turn until you (a) get
an acceptable connection, or (b) determine the â€œbestâ€ firmware for your
combination of ISP, DSLAM and phone line.
filter â€“ a standard ADSL filter is not good enough ! You need an ADSL2
filter which complies with the new Australian Standard AS/ACIFS041:2005. Note that RCIT.0004 is the OLD ADSL1 standard, and some of the cheaper filters actually create interference on the line.
- Often the problem is within your premesis, so perform an Isolation test.
all phones, fax machines, modems, etc. from the phone line used for
your ADSL connection. Now plug in ONLY the ADSL modem and test the
connection. Check the SNR Margin, Loop Attenuation, Up and Down speeds;
as descrived in How can I know if I have a good connection ?.
there is a difference between these values and your normal values, then
connect one other phone device to the phone line, and check the SNR
- Do the same for each phone device you have. This should indicate which (if any) device is causing a problem.
that loose cables and faulty connections can also cause problems, as
can faulty ADSL filters â€“ so you might like to try different
combinations of device / extension socket / cable to determine which of
these is the culprit.
- Try a friendâ€™s
modem on your ADSL line, or try your modem on their ADSL line. This
should help to indicate whether the fault is with the modem or the ADSL
OK, tried all that, but I still have a problem. What next ?
- Document the steps above which you have tried, with the
results. This will save a lot of time for both you and the support
- Email this documentation along with model and firmware version to email@example.com
Finally, after you have determined your speed, we recommend
documenting your current settings and values as a reference point.
Screen dumps of Online Status and other relevant web configurator
pages, pasted into a Word or Wordpad document is easy and worthwhile.
If you want, you can also use the Vigor's telnet interface to document
the various adsl settings, and Mark and Paste this into the document.
Why do this ? Because things can and do change. for example, ADSL performance can errode gradually because of increased crosstalk
or suddenly because your copper pair was swapped. The fact is that
Telstra, ISPs, etc don't tell you about every change which might affect
you (e.g. telephone exchange upgrades, DSLAM firmware upgrades,
swapping copper pairs in your street), and they hope that the change
won't affect you enough to make you complain. From your end, it is a
lot easier to get your problem fixed (or at least reduced) if you can
produce objective evidence (e.g. that your Loop Attenuation was 18.5 on
3rd March, and now it's 65).
Be aware also that your ISP could simply take the attitude that as
long as you get 1.5M/256K speed then you have nothing to complain about
because their ADSL2+ plan is priced the same as 1500/256.