Cable and Antenna Test Mode
R&S
®
Cable Rider ZPH
130
User Manual 1321.0950.02 ─ 07
To draw conclusions about which component is affected and to determine the location
of the fault, you need to perform further analysis using other measurements.
7.1.2
Distance to Fault Measurements
The distance to fault (DTF) measurement determines the exact location of possible
faults in a transmission system. If you connect the end of the cable to the R&S Cable
Rider ZPH, the DTF measurement shows you the exact distance to the fault (in meter
or feet), regardless by what the fault is caused. In addition, the measurement shows
the degree of the fault in dB. From this information, you can determine the component
that has the fault and its seriousness.
In order to determine the distance to a cable fault, the R&S Cable Rider ZPH measures
the reflections of the cable under test in the frequency domain. The R&S Cable Rider
ZPH first determines the magnitude of the reflections for a particular frequency by com-
paring the phase of the reflected signal and a reference signal created by the signal
source. It then performs an inverse fast fourier transformation (IFFT) on the signal that
has been received. In combination with the characteristics of the cable model, the R&S
Cable Rider ZPH is able to determine the distance the reflections have been traveling.
Because of its sensitivity by first measuring in the frequency domain and subsequent
IFFT, the measurement is able to locate faults in a cable accurately. To keep this accu-
racy, the R&S Cable Rider ZPH also accounts for any attenuation that occurs over dis-
tance in a cable.
If you are measuring the cable only, make sure to terminate the other end into a load.
The DTF measurement can be performed in the following measurement formats:
●
Magnitude (return loss in dB)
●
SWR
1. Press the [MEAS] key.
2. Select the "DTF" softkey.
The R&S Cable Rider ZPH displays the submenu to select the measurement for-
mat.
3. Select "Return Loss" or "SWR".
The R&S Cable Rider ZPH calculates the distance to cable faults.
Figure 7-4
shows an example of a DTF measurement in magnitude and SWR mea-
surement format. The peaks that the trace shows at the marker positions are possible
faults. Depending on the distance, you can also get an idea of the component that is
defective.
Marker 1, M1 for example, shows a defect in the cable. Marker 2, M2 shows a fault at
the end of the cable, probably a bad or loose connection.
Performing Cable and Antenna Measurements
