R&S FSH
Cable Measurements
1145.5973.12 4.103
E-11
Cable Measurements
(Only for R&S FSH with tracking generator (R&S FSH3 order No. 1145.5850.13 or 1145.5850.23,
R&S FSH6 order No. 1145.5850.26) and with option R&S FSH-B1 (Distance-To-Fault Measurements)
installed).
Measurements to determine the characteristics of cables to the antenna are key tasks when
transmission equipment is being installed or maintained. Cable damage or bad connections have an
adverse effect on the efficiency of the transmitter system. In conjunction with a tracking generator and
the option "Distance-To-Fault Measurement" (DTF, R&S FSH-B1), the R&S FSH can locate cable faults
and determine their distance from the measurement plane.
The only inputs required are the cable type and the approximate length. Using these parameters, the
R&S FSH measures the distance to any faults and the degree of mismatch. It is easy to define the
cable characteristics with the supplied "FSH View" software package and to transfer them to the
R&S FSH. Up to 100 cable types can be stored by the R&S FSH.
The R&S FSH measures the sum of the tracking generator signal and the signal reflected by the cable
under test in the frequency domain. Depending on the phase of the signal reflected at a fault relative to
the generator signal there is either reinforcement or cancellation. Because of this effect there is ripple
on the received sum signal in the frequency domain. The R&S FSH fast Fourier transforms the received
signal to the time domain. Using the characteristic data of the cable under test, the R&S FSH directly
calculates how far the reflections have travelled from the fault. The magnitude of the fault is given by
the height of the reflection at a certain distance.
Test setup:
Connect the cable of the VSWR Bridge R&S FSH-Z2 or R&S FSH-Z3 to the power sensor input on
the R&S FSH.
Note:
Supplying DC voltage to active DUTS: If the cable to be evaluated contains additional
amplifiers, you can supply them with DC voltage via the RF cable by using the bias tee
integrated in the R&S FSH-Z3. The DC voltage is fed in from a suitable power
supply (max. 300 mA/max. 50 V). For example, a tower-mounted amplifier (TMA) can
be supplied with DC voltage in a mobile radio base station in this manner. This is done
by applying a suitable voltage at the BIAS 1 BNC input of the VSWR bridge.
Connect the bridge to the generator output and the RF input on the R&S FSH.
Connect the cable supplied with option R&S FSH-B1 to the bridge input.
Note:
For distance-to-fault measurements, a cable of one meter length must be connected to to
the test port of the R&S FSH-Z2 or R&S FSH-Z3 . Results are invalid without this cable.
