Kitz ADSL Broadband Information
adsl spacer  
Support this site
Home Broadband ISPs Tech Routers Wiki Forum
 
     
   Compare ISP   Rate your ISP
   Glossary   Glossary
 
Please login or register.

Login with username, password and session length
Advanced search  

News:

Author Topic: Interpreting DMT Graphs  (Read 3175 times)

orainsear

  • Reg Member
  • ***
  • Posts: 635
Interpreting DMT Graphs
« on: October 04, 2008, 11:47:20 AM »

I have attached a snapshot image of my stats taken using the DMT tool.  I am on a fairly long line (~50 dB attenuation).  What I am particularly interested in are the gaps in my spectrum.  Are these acceptable bearing in mind my long line, or is something not quite right at the higher frequencies? 

I'd also like to know why I have a single tone sitting at 725 kHz.  Do these gaps in the spectrum, and the large gap from 656 kHz to 724 kHz indicate interference problems, or is this type of spectrum indicative of a long line?
Logged

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 32609
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: Interpreting DMT Graphs
« Reply #1 on: October 04, 2008, 12:17:19 PM »

Hi

Gaps appear when there is too much noise at a particular frequency to fill the bin.  If a particular bins SNR (note this is SNR not SNRM)  is below 6dB then the router wont use that channel.  This could be due to interference.. or it could be just too attenuated to receive a signal.

Whilst I understand the very basics of DMT modulation, Im not an expert as it also involves some further complicated modulation techniques that would probably require a degree in the subject to understand fully
- but looking at your graph it looks like the decline is normal due to attenuation (loop loss/line length). 
However why you get the one strong signal further on - sorry I dont know :(


Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker
 

anything