Operating instructions

OPERATING MANUAL 2945A
46882-311D A-15
The bar charts can be set for auto-ranging or manual range selection. Repeated presses of the
[Bchart Select] key selects each bar chart in turn. The selected bar chart is indicated by an A or H
being shown in inverse video at the left end.
Pressing the [Autorange] key will switch the selected bar chart to auto-ranging, indicated by an
inverse video A.
To change a bar chart from auto-ranging to a specific range, first select the bar chart using the
[Bchart Select] key, then press the [] key or [] key, until the required range is selected. If the
bar chart was in auto-range mode, the first press of a range change key will place the bar chart in
’Hold’ mode without changing the range.
The bar chart indications of the power measurement range is covered in 10 ranges. The lowest
range has a maximum indication of 30 mW, with 10 mW and 20 mW divisions. The highest range
has a maximum indication of 1 kW, with 0.2, 0.4, 0.6 and 0.8 kW divisions. Between these, the
ranges continue in a 1, 3, 10 sequence.
The directional power head is able to measure RF powers over a large dynamic range, from 5 mW
to 400 W. The measuring circuits integrate readings over a finite period and therefore the accuracy
of the readings obtained from amplitude modulated signals would depend on the content of the
signal being measured.
For making measurements on CW, FM and phase modulated signals the CW measuring system is
selected.
When it is required to make power measurements on amplitude modulated or single side band
signals the PEP (Peak Envelope Power) system is selected. The range of measurement covered by
the PEP system is from 1 W to 400 W.
The selection of CW or PEP measurements is made using the [CW/PEP] key. The selection is
indicated by the legend Measuring CW or Measuring PEP displayed above the forward power
measurement.
VSWR is shown digitally and also on a bar chart at the bottom of the display. The VSWR range is
covered in two steps as shown below:-
1.0 (:1) to 2.0 (:1) ...................................................................... with 1.2, 1.4, 1.6, 1.8 (:1) divisions.
1.0 (:1) to 4.0 (:1) .......................................................................................... with 2, 3 (:1) divisions.