HP 8560A, Service Manual

Page: 291 / 450

Table 8-3. Sweep Width Settings
Sweep Width Sweep Time RES BW RANGE MA1 MAO
Adjusted
20 5 ms 10
V 0V 0V
10
10 ms 3
V 0 V
4 30 ms 1
+5 V +5 V 0 V
2 60 ms 300 Hz +5 V
V V
Automatic IF Adjustment
The spectrum analyzer performs an automatic adjustment of the IF Section whenever needed.
The Cal Oscillator on the A4 assembly provides a stimulus signal which is routed through the
IF during the retrace period.
The A3 Interface assembly measures the response using its analog-to-digital converter
(ADC).
The spectrum analyzer turns the Cal Oscillator off during a sweep.
When IF ADJ is on, the analyzer readjusts part of the IF circuitry during each retrace period
to readjust the IF completely every 5 minutes.
Automatic IF adjustment is performed upon the following conditions:
Power on:
(unless
STOP ALIGN
is pressed). The IF parameter variables are initialized to
values loaded in program ROM and all possible IF adjustments are made. If
STOP ALIGN is
pressed, the adjustment is halted.
n
If
REALIGN LO IF
is selected: All possible IF adjustments (and LO adjustments) are
made with the most recent IF parameter variables used as the starting point.
If
FULL IF ADJ
is selected: All possible IF adjustments are made with the most recent IF
parameter variables used as the starting point.
(FULL IF ADJ
is located in the menu.)
If
ADJ CURR IF STATE
is selected: All amplitude data and some resolution bandwidths
are adjusted. The bandwidths adjusted are a function of the currently selected resolution
bandwidth setting.
n
Between
sweeps:
IF ADJ must be set to on. When IF ADJ is off, an
A
is displayed along
the left side of the graticule.
If a FULL IF ADJ sequence cannot proceed beyond the amplitude portion, check the output
of the A4 Cal Oscillator as follows:
1. Disconnect cable W52 (coax 9) from Connect cable W52 to the input of a second
spectrum analyzer.
2. Set the second spectrum analyzer center frequency to 10.7 MHz and the reference level to
- 3 0
3. On the spectrum analyzer under test, press
FULL IF ADJ
and observe the display of the
second spectrum analyzer
4. If a -35 signal does not appear, the A4 Cal Oscillator is probably at fault.
IF Section 8-9