Technical data

Chapter 10 281
Distance to Fault
Measuring Distance to Fault
Distance to Fault
In most cases, the default resolution using 256 data points will be adequate to
locate the faults, but if more resolution is needed you can increase the span
between the start and stop frequencies (which will decrease the measured
distance) or use the other approach, automatic frequency range. If the
measurement distance is not long enough for the cable you are testing, reduce
the span between the start and stop frequencies (which will increase the
measurement distance) or use automatic frequency range.
NOTE When testing cables attached to antennas, test signals are radiated from the test
antenna. Verify that the signal used for the test, and therefore being radiated from
the test antenna, cannot interfere with other radiated signals from other antennas.
Calibration - Minimizing your Workload
The Distance to Fault calibration (when it is performed with Frequency Range set
to manual) is the same calibration as performed for the
Return Loss and One-Port
Insertion Loss
measurements. If you have already calibrated for any of these three
measurements, the calibration will apply to the other two measurements and
“Calibrated” (together with the frequency range over which the calibration was
performed) will be displayed on top left of the screen for all three if the Start and
Stop frequencies are set within the calibrated frequency range.
The
Distance to Fault calibration (when it is performed with Frequency Range set
to Auto) is only valid for other Distance to Fault measurements that are also
performed with Frequency Range set to Auto, and then only if the Start and Stop
frequencies fall within the previously calibrated frequency range.
If you have not previously performed a calibration, the word “Uncalibrated” appears
at the top left of the measurement screen.
It is important that you keep the calibration frequency range as close as possible to
the actual sweep frequencies you intend using for the measurement or
measurements. Calibrating over a large frequency range (for example, 1 GHz) when
you only intend measuring over a much smaller range (a few kHz, for example) will
reduce your measurement accuracy.
If you plan to perform a combination of
One-Port Insertion Loss measurement,
Return Loss measurement, and Distance to Fault measurements using a frequency
range that you will set manually, you can perform one calibration for all three
measurements as long as you calibrate over a frequency range that incorporates all
three of your measurements, and as long as your cables do not change. For this
reason, if you are doing Distance to Fault measurements (using a frequency range
that you have set manually) as well as any type of Insertion Loss measurement,