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14. External Mixer Bias Adjustment (Non-Option 327)
Assembly
Adjusted
Al5 RF assembly
Related
Performance
Test
There is no related performance test for this adjustment.
Description
A voltmeter is connected to the spectrum analyzer IF INPUT with the external mixer bias set
to off. The bias is adjusted for a 0 Vdc output.
Equipment
DVM . . . . .
DIGITAL VOLTMETER
Al5 RF
Al4
SPECTRUM
ANALYZER
Figure 2-23. External Mixer Bias Adjustment Setup
SK116
,.....................................................
HP 3456A
Adapters
Type BNC (f) to SMA (m)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1250-1200
Type BNC (f) to dual banana plug
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1251-2816
Cables
BNC,122cm
(48in)............................................
HP 10503A
Procedure
1. Press luNE) to turn the spectrum analyzer off, and disconnect the ac power cord. Remove
the spectrum analyzer cover and connect the equipment as illustrated in Figure 2-23. Fold
down the Al5 RF assembly. Reconnect the power cord and set the luNE) switch to on.
2. Set the HP 3456A controls as follows:
Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DC VOLTS
Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..O.lV
Resolution
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lOOmV
3. On the spectrum analyzer press
(AUXCTRL),
EXTERNAL
MIXER,
BIAS, then
BIAS
OFF.
4. Adjust A15R926 EXT BIAS ZERO for a DVM reading of 0.000 Vdc f12.5 mV.
2-56 Adjustment Procedures