R&S ZVH
Cable and Antenna Test Mode
Performing Cable and Antenna Measurements
Operating Manual 1309.6946.12 - 09
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2.1.2 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 ZVH,
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 ZVH measures the
reflections of the cable under test in the frequency domain. The R&S ZVH first
determines the magnitude of the reflections for a particular frequency by comparing the
phase of the reflected signal and a reference signal created by the tracking generator.
It then performs inverse fast fourier transformation (IFFT) on the signal that has been
received. In combination with the characteristics of the cable model, the R&S ZVH is
able to determine the distance the reflections have been travelling.
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
accuracy, the R&S ZVH also accounts for any attenuation that occurs over distance in
a cable.
If you are measuring the cable only, make sure to terminate the other end into a load.
► Press the MEAS key.
► Press the "Distance to Fault"
softkey.
The R&S ZVH calculates the
distance to cable faults.
The figure shows the results of a DTF
measurement. 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, for example, shows a defect in the cable. Marker 2 shows a fault at the end
of the cable, probably a bad or loose connection.
