HP 85106D, Manual

Page: 198 / 244

HP 85106D mm-Wave System 6-33
HP 85105A mm-Wave Controller
LO ALC Adjustment
1. Run the system software and select {
HIGHBAND
} to make the mm-wave
controller active.
2. Check the user parameter (al or a2) for the LO port in question. The
trace should be -15
±
2 dBm across the band as displayed on the
HP 8510 CRT. If this is the case the LO ALC is adjusted properly.
If the message
NO IF FOUND
is displayed and/or a trace is not observed
at the level mentioned, the LO ALC adjustment needs to be made,
continue with step 3.
NOTE
Step 3 should only be performed when an amplifier, coupler, or detector has
been replaced.
3. Connect the oscilloscope and negative detector as shown in Figure 6-16
on page 6-32. Turn the gain adjustment fully clockwise. Oscillations
should be visible on the oscilloscope. Turn the gain adjustment counter
clockwise until the oscillations just disappear. Recheck the user
parameters in step 2 and then continue with step 4.
4. Choose a power meter that covers the 4 to 6 GHz frequency range
(HP 436A meter and HP 8485A sensor). Calibrate the power meter
and attach a 3.5 mm 10 dB fixed attenuator (HP 8493C) and an adapter
(female to female) to the sensor. Connect the sensor/attenuator to the LO
output of the port in question. Turn the LO level adjustment so that
+12 dBm is displayed on the power meter. The LO output is now set at
+22 dBm. Select {
SINGLE POINT MODE
} from the [
STIMULUS
] menu, then
using the RPG knob, slowly scan over the frequency band.
5. Adjust the LEVEL pot over the full adjustment range to make sure there
are no oscillations at any power level. Then turn the GAIN pot three
additional turns.