24 • BX-245
© Box 73 Amateurfunkservice GmbH 2019
Delta Frequency
This allows for optional Frequency Cor-
rection of the internal oscillator. All inter-
nal frequency values are derived from a
high quality 26MHz temperature-con-
trolled crystal oscillator (TCXO), which
inherently has very little frequency devia-
tion or drift. Any remaining residual devi-
ation can be compensated by software. For
this purpose, first set a frequency of
26.000000 MHz in the
frequency genera-
tor
mode. Then connect a calibrated fre-
quency counter to the BNC output connec-
tor of the Analyzer and determine the
difference between the measured and the
displayed frequency. After selecting the
Correction Frequency
menu item, first
press the left
button. Then the value
for df is set to the determined difference
using the middle and right buttons (mea-
sured frequency minus 26.000000MHz).
The
button is again used to select the
decimal place. Repeatedly pressing this
button leads to the display of the abbrevi-
ation ENT (Fig. 48). When the
or
button is pressed, the FA-VA5 accepts the
value set as the frequency correction.
Thereafter, the frequency of the Analyzer
output signal should be exactly equal to the
set frequency. It should be noted, however,
that this frequency correction is usually not
required for antenna measurements.
SOL = Calibration On / Off
If required, the stored calibration can be
switched on / off via menu item
SOL
. This
can be useful if there are doubts about the
validity of the stored data, for example.
ZO Base = Reference impedance
SWR measurement values refer to a system
impedance
Z
0
. This reference impedance
can be selected via the menu item
Z0 Base
(Fig. 49) which is displayed at the right
edge of the display during measurement
(see section Measurements with the FA-
VA5).
Available settings are: ZO =25 Ohm, ZO
= 50 Ohm (default setting) and ZO = 75
Ohm)
Impedance Model
The FA-VA5 can display the impedance in
either of the corresponding measurement
modes as either a Serial (default setting)
or Parallel model. At the same time, the
calculation of the equivalent capacitance /
inductance of the imaginary part for a se-
rial or parallel equivalent element is per-
formed. The selection is made in the menu
item
Impedance Model
.
Fig. 47: Setup mode, fourth section
Fig. 48: Input option for the correction of the
frequency offset
Fig. 49: Selection options for the Reference
impedance basis
