Quick Installation Guide

Document

WERA4-Quick-US-200918

Page 39 of 73

Some portable spectrum analyzers like the Rohde & Schwarz FSH3 with build-in tracking

generator got the option to measure phases relative to a calibrated reference cable after

performing an open/short/load calibration at the end of the reference cable.

There is a separate document describing in detail how to perform such a calibration

measurement with this analyzer model. See the document “WERA-Cable-calibration_using

FSH3-150907.pdf” for details.

Other analyzers might be used in a similar way.

The resulting phase values are not as stable as when using the 1:16 calibration splitter

box. Additionally it must be kept in mind that the displayed phase values are results from a

reflection measurement and thus the values need to be divided by 2 to retrieve the correct

values for the calibration table.

5.11.3.3 Calibration with precise TDR

If all receive cables are from the same manufacturing batch and thus got exactly the

same velocity factor, then an alternative method is to use a very precise Time-Domain-

Analyser TDR and measure the differences in cable length. With these values known, and

the correct velocity factor for the cables, the according phase difference to cable 1 can be

calculated. That means a cable that is longer than cable #1 will have a positive phase

value. These calculated phase values need to be subtracted from the phases values of

the internal calibration. For this the file calibration.wera_internal need to be edited and

the modified file should be stored as calibration.wera in the .etc folder.

But beware ! - If it is not known, if all cables are from the same batch, the velocity factors

may be different and then the calculated phase differences would be wrong.

So the other mentioned calibration methods are preferred.

5.13 Connect all RX antennas

Now all Rx antennas can be connected, but do not seal them now. The coax cables should

be placed in their final position.

5.14 Connect Tx array

Now connect the one already tuned Tx antenna direct to the Tx cable (a female-female N

connector is required).

The Tx cable can be connected to power amplifier (PA) output, but ensure to switch the

PA to lowest gain (turn knob to left most position or use “PA” setup section of

“WERA Remote control” software if remote controlled PA).

Start a Calibration under the WERA Control Center. 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 no RMS-Voltage should be higher than 7 Volts. No voltage should be

>7 Volts but it should be >1 Volt.