6. Video Processor Adjustments
IF-Display Section
Video Processor
Log Scale Switching Uncertainty Test
The CAL OUTPUT signal is connected to the RF INPUT through a
step attenuator. The instrument is placed in zero frequency span to
produce a dc level output from the log amplifier. The
ZERO
adjustment, which sets the dc offset of the output buffer amplifier of
the log board, is checked and adjusted if necessary. The dc level into
the video processor is is adjusted by’varying the input signal level and
reference level. The offsets and gains on the
Video Processor
are adjusted for proper levels using a DVM.
S T E P A T T E N U A T O R
Figure 3-35. Video Processor Adjustments Setup
Digital Voltmeter (DVM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HP 3456A
10
Step Attenuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .HP 355D
The voltage at
may drift noticeably with temperature
during this adjustment. Allow the
Video Processor to warm up
at least one-half hour prior to adjustment.
2.
3.
4.
5.
Position the spectrum analyzer upright as shown in Figure 3-35.
Remove the IF-Display Section top cover.
Set the spectrum analyzer LINE switch to ON and press
Connect DVM to
and DVM ground to
the
IF casting.
Connect CAL OUTPUT to RF INPUT through 10
step
attenuator.
Key in
[
CENTER FREQUENCY
]
100 MHz and
[
FREQUENCY SPAN
)
0 Hz.
Press the LIN pushbutton.
Adjustments 3-73
