HP 8414A Operating And Service Manual page 19

Model 8414A
Section III
Operation
REFLECTION COEFFICIENT MEASUREMENT
CALIBRATION
1. Connect equipment as shown in setup.
2. Connect a coaxial short such as the HP
11565A to the reflectometer unknown
port.
3. Phase lock the Network Analyzer over the
desired frequency band.
4. Push and hold the 8414A BEAM CTR push¬
button and adjust HORIZ POS and VERT
POS controls to place the dot in the center
of the graticule. To bring the dot onto the
display rotate each positioning control
about five turns counterclockwise or until a
slight increase in resistance to movement is
encountered. Then turn each control about
two and one-half turns clockwise.
NOTE
If an input signal does nit deflect the
CRT beam, SI, the TEST-NORMAL
switch, may be in the TEST position.
Refer to Figure 8-24 (last foldout) for
location of SI and set SI to
NORMAL.
5. Obtain equal reference and test channel
electrical lengths by adjusting the Line
Stretcher to collapse the trace to a dot or
smallest cluster.
6. Adjust the Network Analyzer phase vernier,
test channel gain1 and amplitude vernier
controls to place the dot or cluster for a
reference indication of F = 1 /_180° (see
Figure 3-11, Display B).
MEASUREMENT
1. Remove the coaxial short and connect the
device under test to the reflectometer un¬
known port.
2. Read the reflection coefficient, magnitude
and phase (or impedance using a Smith
Chart overlay) from the display.
NOTE
For small reflection coefficients the
8414A resolution can be improved by
increasing the Network Analyzer test
channel gain1. For example, increas¬
ing the test channel gain1 by 20 dB
changes the full scale calibration from
1.0 to 0.1 at the outer circle (see para¬
graph 3-10). For increased accuracy
by minimizing directivity errors, see
paragraph 3-33.
^Display reference for 8407A.
Figure 3-9. Reflection Coefficient Measurement (Sheet 2 of 2)
3-9