Service manual

12 Agilent 382A Operating and Service Manual
Operation
Moding Test The following test determines that the attenuator is functioning at all
frequencies and not just at the test frequencies. If the attenuator does not
attenuate at certain frequencies (moding) spikes will appear on the
attenuation curve. To obtain this curve proceed as follows:
1. Connect instruments are show in Figure 4.
2. Set 382A under test to 50 dB.
3. Sweep a line for the entire frequency band of the 382A under test. There
should not be any deviations from this curve such as spikes, etc. If such
deviations exist change the center-section and retest.
Figure 4 Moding Test Setup
NOTE *If SWR meter has switch, set MTR damp switch to out.
Backlash Backlash must be checked before the calibration on the attenuator since any
calibration done will be nullified if excessive backlash exists. To check
backlash proceed as follows:
1. Connect instruments as shown in Figure3 on page11.
2. Set the 382A under test to the 50 dB calibration mark.
3. Set variable attenuator for a reference on the SWR meter.
4. Move dial to the right and then back to 50 dB. Read SWR meter.
5. Move dial to left and then back to 50 dB. In both this step and the
preceding step the deviation of the meter from the reference point should
not exceed ±0. 2 dB.