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3.
On the Model 416A, set the RANGE switch
at
0 DB
100%.
There is a short across the line
,
and therefore there now exists a
condition of 100% reflection.
Essentially,
the following signals are
entering the Model 416A
:
at
the REFLECTED/PROBE input, a volt-
age proportional to the 100% reflection; at the INCIDENT
/REFERENCE
input: ( 1) a
voltage
proportional to the incident power, and (2) an
error signal proportional to the reflection from the load.
4.
Adjustment of the Model X920A adjusts the phase of the reflection
from the short and therefore the phase of the
error
signal.
Adjust the Model X920A to obtain ( 1) a maximum indication on the
Model 416A meter,
and
(2) a minimum indication.
Referred to the reflected detector
,
the change in phase of the error
signal may be
considered to
be adding to or subtracting from the re-
flected
voltage
to give
a
maximum and a minimum reflection coef
-
ficient reading.
5.
Note the maximum and minim.um readings, and determine the differ-
ence between the two
.
For example, if the maximum
indication is
99% and the minimum is
95%, there
is
a 4% difference.
6
.
To calibrate the system for 100% reflection
,
so adjust
the
SET TO
FULL SCALE control on the Model 416A that the midpoint of the max-
mm difference would be a 100% meter indication.
For example, for the readings
given
above
,
the minimum indication
should be 98% and the maximum
,
102%.
Though
the
adjustment
may be made at either the max or min end, since 102%
is
off the scale
and
would have to be approximated
,
it
is
suggested that the adjustment
of the SET TO FULL SCALE
control
be made when the short is in the
position where the minimum
reading
occurs.
a.
Adjust the Model X920A to obtain the minimum indication, 95%.
b
.
On the Model 416A, adjust SET TO FULL SCALE to bring this
minimum indication up to 98%
.
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