Limit is reported as 0 dB (zero dB) | Fluke Networks

Knowledge Base

KB Home   >  Copper Testing   >  LinkWare™ PC 6.2

Limit is reported as 0 dB (zero dB)

This is caused by the 3 dB rule for return loss and 4 dB rule found in ISO/IEC 11801:2002 and EN50173:2002.
 
These rules require the tester to ignore the measurement when the attenuation is less than 3 dB or 4 dB dependant up on the parameter being measured.
 
On a short link, the attenuation will not exceed 3 dB or 4 dB. In this case the entire frequency range falls within the 3 dB and 4 dB rule. The result of this is that the entire measurement is ignored. So how do we report it? We make the limit 0 dB, and then report the worst case value. That is why you occasionally see large headroom figures such as 48.9 dB.
 
Still not clear? support@flukenetworks.com
 

 

Author: Adrian Young

Creation Date: 2014-02-24

Last Modified: 2014-02-24