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7-6
Adjustments and Calibration
Sum Loop Adjustment Procedure
Sum Loop Adjustment Procedure
This procedure should be performed whenever Step Loop A Assembly (A26) or Sum
Loop Assembly (A25) is replaced. It is not necessary to perform this adjustment for a
periodic calibration.
A spectrum analyzer is required to measure the instrument’s output during these
procedures. It is recommended to use a synthesized spectrum analyzer if possible.
Procedure:
1. Turn off the HP/Agilent 8922.
2. Remove the instrument top cover and the DAC/Upconverter Module (A27). (It is
necessary to remove the RF Cover plate that holds the module in the instrument.)
3. Power up the instrument, select the RF GENERATOR/RF ANALYZER screen, and set
the RF Gen Amplitude to −20 dBm at the RF IN/OUT connector.
4. Prepare the spectrum analyzer. Set the reference level to −10 dBm. Connect the HP/
Agilent 8922 RF IN/OUT to the spectrum analyzer input.
First Adjustment
5. Again from the RF GENERATOR screen, set the HP/Agilent 8922 frequency to 800
MHz.
6. Set the spectrum analyzer center frequency to 786.6 MHz. (The output from the HP/
Agilent 8922 is 13.4 MHz lower than was entered because the DAC/Upconverter is
gone).
7. Set the spectrum analyzer span to 10 MHz per division. ADJUST R32 “OFFSET” on
top of Sum Loop (A25) until the signal on the spectrum analyzer is between 776.6 and
796.6 MHz.
8. Reduce the spectrum analyzer span to 1 MHz per division and adjust R32 again until
the signal on the spectrum analyzer is centered within 2 divisions (2 MHz).
NOTE Some modules (prefix 3050A and lower) only need to be centered within 10 MHz for all
of these adjustments.