Measuring Distance To Fault - Motorola PTP 800 User Manual

Testing the installation

Measuring distance to fault

The distance to fault (DTF) test is used as a means of characterizing the cable
installation, but can also be used determine the location of a fault in an installation.
Before performing this test, ensure that the test equipment is set up as described in
Test preparation
To measure distance to fault, proceed as follows:
Procedure 5-16 Measure distance to fault
Select the 'DTF-return loss' mode of the cable analyzer
1
5-17).
2 Select 'DTF Aid'.
3 Use the up/down key to select and set the following:
Cable type - select LMR400 (similar to CNT400).
F2 - select the highest frequency possible for the greatest
resolution, 1600 MHz.
D1 and D2 - set as appropriate for the specific installation.
Recalibrate the instrument.
4
5 Before connecting the ODU, obtain a plot of DTF loss. Compare
it to an example of a good installation
Connect the ODU.
6
Observe the effect of the ODU connection on the DTF plot.
7
Compare it to an example of a good installation
8 Keep a copy of the DTF plots so that they can be compared with
subsequent plots to determine if there is any degradation with
time.
NOTE
5-84
on page 5-78.
The absolute readings of DTF should be read with care, as many different
variables affect both distance and amplitude accuracy.
(Figure
(Figure 5-23).
(Figure 5-24).
phn-1478_005v000
Chapter 5 Installation
Apr 2010