Quick Installation Guide
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WERA4-Quick-US-200917
Page 38 of 73
5.11.3 Cable Calibration
This calibration is essential for the operation of the WERA system. Normally this
calibration was already carried out at the factory.
In that case the calibration is already activated and should not be run again!
If the cable calibration needs to be carried out in the field there are several options.
5.11.3.1 Calibration with Calibration Box (1:16 Splitter)
All cable ends should be labelled with the correct receive channel number.
In any case the “Receiver Input” of all channels needs to be connected to the lightning
arrestor plate or for WERA IV to the Receiver Input filters.
All Rx coax cables need to be connected to the input of the lightning arrestor plate.
The cables can be calibrated before they are rolled out. In that case all Rx cables spools
need to be placed next to the lightning arrestor plate to be connected.
All other ends of the Rx cables should be connected to the Calibration Box.
One extra coax cable need to be connected from the Tx driver output (chapter 4 page 2).
(
Attention
, never use the output from the Power Amplifier for the calibration). This cable
need to be connected to the centre connection of the “Calibration Box”.
Start a
Calibration
under the WERA Control Centre. Use settings for a short run:
256 samples, 0.260 sec sweep time, 80 Hz offset
Check the results using “Plott_WERA_Cal_lsq
”
according to the description in pos. 11.7.
In the resulting table all RMS-Voltage
should be almost identical and the “
Cal values”
should be between 1.0 and 1.1.
If this is not the case the according cable or connector has a problem.
In the second part of the table are the phase values listed. At the
“Peak”
the phase should
be b30 to -30 degrees.
If this is not the case one of the cables has a different length (outside of normal tolerance).
Phase differences of up to 180° can be compensated by the WERA software.
Nevertheless such a cable is suspicious and should be double checked.
If the results are ok, the calibration file (.amphase) should be copied into the directory
/home/wera/etc/ and renamed to
calibration.wera.
Additionally this should be noted in
the log book.
Now this calibration is activated
and will be used for all measurements.
Note that some programs may need to be restarted to use the modified calibration
constants.
This calibration procedure can also be carried out
with the cables already laid out
. In
that case the cable ends need to be collected in the field and connected to the Calibration
Box. The input of the Calibration Box needs to be connected with a long cable to the “TX-
Out” output of the Frequency Control Rack (FCR).
Normally no power amplifier should be used for this type of calibration to avoid damaging
the 1:16 calibration splitter box or the receiver input filters.
5.11.3.2 Calibration with special Spectrum analyser
