34 • BX-245
© Box 73 Amateurfunkservice GmbH 2019
n
FA-VA5 as USB measuring
Front-end
USB measuring Front-end means that the
PC software VNWA takes over the entire
control and evaluation of a measurement.
In simple terms, the FA-VA5 in this case
only supplies the requested measurement
voltage for a frequency specified by VN-
WA. Thus, for example, parameters of a
multi-frequency measurement, such as the
number of measuring points (instead of the
locally fixed 100 points) can be specified
within given limits. In the following sec-
tions, a simplified measurement explains
the procedure as an example, with values
to be determined for SWR and impedance.
Step 1: Definition of the measuring
parameters
First the start and stop frequencies have to
be entered. In the main window of VNWA
(Fig. 56), this can easily be done by dou-
ble-clicking on one of the frequencies dis-
played below the bottom of the Grid: left=
Start, middle=centre or right=Stop fre-
quency. The frequency window (
Input
)
will open and allows you to enter the start
and stop frequency of a multi-frequency
pass. Note the decimal point as a division
between pre- and post-decimal places. For
the example, 6MHz to 10MHz was select-
ed in Fig. 64. Further parameters are de-
vice-specific and can be set for the FA-
VA5 via the familiar window according to
Fig. 58 (
Settings
→
Sweep
). In addition to
the
Number of Datapoints
, one of the three
FA-VA5 (
sweep mode
) accuracy levels
can be selected:
fast
,
standard
, or
precise
.
In addition, another delay per measured
value can be set (
additional delay
). This
can be useful when measuring low-fre-
quency filters, which have a long settling
time. VNWA calculates the resulting time
for the multi-frequency measurement. The
Fig. 63: Context menu when adding a frequency marker; the data of marker 1 (Arrow) can be
seen in the upper left corner of the diagram (framed in red).
