Rohde & Schwarz ZVB 14, Service Manual

Page: 143 / 198

R&S ZVB Instrument Construction and Function Description
1145.1078.82 3.75 E-4
Frequency Output level Displayed level
ax or bx
300 kHz -20 dBm 0 dBm
50 MHz -20 dBm 0 dBm
1 GHz -20 dBm 0 dBm
3 GHz -20 dBm 0 dBm
6 GHz -20 dBm 0 dBm
8 GHz -20 dBm 0 dBm
With the stated levels, the cable loss must still be taken into account. For the specified cable, it is
0.25 dB/GHz (0.5 m) or. 0.5 dB/GHz (1 m).
If the measured values are more than 2 dB below the levels and ratios list in the table, the board must
be replaced.
Bridge unit levels
The following is assumed:
•
One reflectometer in the instrument is OK.
Method 1:
The generator section of the associated reflectometer is OK (output level at the port meets
specifications).
Loosen cable W515 (Bridge unit -> MEAS) and cable W518 (Bridge unit -> REF) at both ends and
disconnect at the bridge unit.
N.B.: When loosening, support the cable with a 7 mm spanner
Connect the bridge unit output (MEAS = connector W515 or REF = connector W518) to a
functioning port using the SMA cable and adapter SMA-N to a functioning port. Terminate the
bridge unit output that is not used with an SMA termination.
Screw a SHORT from the N calibration kit to the port connector.
Set the frequencies and levels listed in the table for the reflectometer associated with the bridge
unit (port) and measure the level (wave quantity bx) at the port used for the measurement.