OBID i-
scan
®
Installation
ID ISC.MAT-A
FEIG ELECTRONIC GmbH
Page 25 of 28
M21200-0de-ID-B.doc
E N
G
L I S H
This is set in the following steps:
6. Change the capacitances C
2,1
and C
2,2
with the jumper strips X2, X3 and trim capacitors C2, C3
to the value most closely approximating R=50
Ω
. Approximately the same values should
always be set on jumper strips X2 and X3.
7. Set capacitance C
1
on jumper strip X4 and the trim capacitors C1, C40 to the value closest to
X=0
Ω
(and R=50
Ω
).
8. Change the capacitances C
2,1
and C
2,2
on jumper strips X2, X3 and trim capacitors C2, C3 to
the value closest to R=50
Ω
and X=0
Ω
. Approximately the same values should always be set
on jumper strips X2 and X3.
9. Set capacitance C
1
on jumper strip X4 and trim capacitors C1, C40 to the value closest to X=0
Ω
and R=50
Ω
.
10. If necessary repeat steps 3+4 until the working point 50
Ω
reaches the specified tolerance (+-
3
Ω
) and no further improvement is possible.
Fig. 12: Two trim capacitors at the same capacitance
After tuning the respective associated trim capacitors should always to set to the same
capacitance.
Note the following when tuning the antenna:
•
The curve for resistance R has two points where the 50
Ω
line is intersected.
•
For very small measured values of R (R < 10
Ω
), the capacitances C
2,1
and C
2,2
must be
increased or decreased in large intervals.
•
The curve for reactance X also has two points where the 0
Ω
line is intersected.
•
Each time the capacitances are changed you must check whether the working point is moving
in the proper direction.
•
By increasing capacitances C
2,1
and C
2,2
you are shifting the curve (Fig. 5) for resistance R to
the left and the two intersection points with the 50
Ω
drift in the direction of a smaller frequency.
•
By increasing C
1
the curve shifts (Bild 5) for the reactance down to smaller values.
•
Changes in the distance to metals, magnetic materials or to the floor will subsequently detune
the antenna, which must then be recalibrated following installation.
Caution: Voltages of up to 1000V may be present on the antenna conductor or on various
components of the tuning boards.
It is also possible to tune the antenna using an SWR meter according to the same procedure, but
this is significantly more difficult since only one measured value at a time (SWR instead of R & X)
is available.
