HP 8901B Operation And Calibration Manual page 401

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 a m .
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