Fluke DTX-1800, Technical Reference Handbook

Page: 116 / 398

DTX Series CableAnalyzer
Technical Reference Handbook
3-30
NEXT and ACR-F performance tends to be similar in cable,
but may differ greatly in connecting hardware. Some
connectors achieve good NEXT performance by balancing
the inductive and capacitive currents that cause crosstalk.
Since these currents are 180
°
out of phase at the near-end
of the cabling, they cancel out, which eliminates crosstalk at
the near end. However, currents that cancel at the near end
add up at the far end, causing far-end crosstalk and poor
ACR-F performance.
Figure 3-23 describes the ACR-F plot.
PS ACR-F Test
Note
PS ACR-F is also known as PSELFEXT (power sum
attenuation to crosstalk ratio, far-end).
PS ACR-F results show how much the far end of each cable
pair is affected by the combined far-end crosstalk from the
other pairs. PS ACR-F is the difference (in dB) between the
test signal and the crosstalk from the other pairs received at
the far end of the cabling. The tester uses the ACR-F values
to calculate PS ACR-F. Higher PS ACR-F values correspond to
better cabling performance.
PS ACR-F results are typically a few dB lower than worst-
case ACR-F results.
Note
The 67 dB rule may apply to your PS ACR-F results.
See page 3-13.