Adjustments Model 8901B
Adjustment
5
LO
DOUBLER OUTPUT POWER AND BALANCE
0
Service
Sheet
17
Description
The power from the LO
is
monitored with a power meter while the
LO
is
stepped through
its
doubler
band. The bias and coupling components are changed
as
necessary
to
obtain the required power output.
The
LO
is
then monitored on
a
spectrum analyzer
as
the
LO
is
swept slowly over
its
doubler band.
The doubler balance
is
adjusted for minimum
112
and
312
harmonics of the doubled frequency.
NOTE
Excessive subharmonics can cause the
Lo
to tune to a wrong frequency
when automatically tuning.
Equipment
Sensor Module
..................................................................
HP 11722A
RF
Spectrum Analyzer
......................................................
HP 8559A1182T
Procedure
NOTE
In the following procedure, a power meter and power sensor combination
can be substituted for the sensor module. The Modulation Analyzer can
then be left in the frequency measurement mode.
1.
Connect the sensor module
to
the Modulation Analyzer’s SENSOR and INPUT connectors.
2. On the Modulation Analyzer, press the blue key then press INSTR PRESET (the AUTOMATIC
OPERATION key)
to
preset the instrument.
3.
Zero
and
calibrate the sensor module using the
RF
power calibrator in the Modulation Analyzer.
Set LOG/LIN
to
read in am.
4.
Connect the sensor module’s input directly
to
A19J3
(LO
OUT), or for Option 003, the rear-panel
LO OUTPUT connector.
5.
On the Modulation Analyzer, press FREQ. Key in
650
MHz
to
set the
LO
to the bottom of
its
doubler band.
6.
Step the
LO
frequency up in
50
000
kHz steps. (Key in
50
000
d
kHz for the
first
step, then
fi
kHz thereafter.) For each step, press FREQ
to
tune the
LO,
then press RF POWER and note the
power reading.
Do
this until Error
20
or Error 15
is
displayed. (The
LO
has
reached the top of
its
range or the frequency
is
beyond the range of the calibration factors of the sensor module.)
The power readings should be between +1.4 and t-3.0 dBm.
If
the power readings are within
range, continue with step
7.
If
the power readings are out of range, change the components on
A19 according
to
the following guidelines.
a. To increase the power throughout the entire doubler band, decrease the value of A19R63.
(Use values within the range 38.1
to
1lOn.)
b.
To
eliminate low-frequency roll-off, increase the value
of
A10C43.
Do
not use a value of
C43 that
is
larger than necessary or the effectiveness of the high-pass filter
is
reduced. (Use
values within the range 4.7
to
15 pF.)
5-10
Adjustment
5
To Next Page
Loading...
Need help?
General
