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HP 85027A/B/C Adjustments
5.
Remove the printed, plastic switch configuration label from the back of the
bridge (additional labels are available as HP P/N 85027-80004).
6.
Disconnect the power sensor from the attenuator. Turn on modulation.
Con¬
nect the bridge input port to the attenuator, leaving the test port open.
7.
On the analyzer, turn on averaging (avg. factor =8), and the cursor. On the HP
8757A, turn on smoothing (5%).
8.
Adjust R5 (see Figure 5-2) for a cursor reading of -6 ±0.1 dBm.
9.
Set the attenuator to 30 dB.
Adjust R29 (Figure 5-2) for a cursor reading of
calibrated -30 dB minus 6 ±0.1 dBm.
10. Set the attenuator to 0 dB and adjust R29 (if required) until the cursor reads -6
±0.1 dBm.
11. Repeat steps 8 through 10 until the change in level is equal to the calibrated 30
dB±0.1 dB and, with 0 dB attenuation, the cursor indicates -6 ±0.1 dBm.
DC Adjustment Procedure
NOTE: You can perform this DC procedure only with an HP 8757A analyzer.
12. On the HP 8757A, set DC mode.
13. Set the reference level to -50 dBm at midscreen, and the scale to 5 dB/div.
14. On the source, turn off the RF power.
15. On the analyzer, press [CAL] [CONFIG SYSTEM],
If your analyzer has firm¬
ware revision 2.0 or above, press [CAL] and select [MORE] [AUTOCAL], to turn
auto calibration OFF.
16. On the bridge, use a short jumper to short pad Y (where yellow wire termi¬
nates) to ground.
17. Adjust R25 (Figure 5-2) for a minimum reading on the analyzer (it should be < -
50 dBm).
18. Remove the short, and turn auto cal back ON.
Feedthru Null Adjustment Procedure
19. On the analyzer, press [CAL] and select [DC DET ZERO] [AUTOZERO].
20. Adjust R10 (Figure 5-2) for as HIGH a trace as possible. Adjust slowly, because
averaging and smoothing mask adjustment effects.
NOTE: Steps 19 and 20 must be repeated until no further change is noted.
5-3
UPDATES APPLY TO ALL SERIALS
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