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The assembly contains a reference limiting amplifier. This amplifier provides a known amount
of limiting for the automatic IF adjustment routines. (Limiting occurs only during the
automatic IF adjustment routines.) The
LC34Short
switches are open during sweeps. The
current in the reference limiter is increased during sweeps to prevent limiting.
Caution
For troubleshooting, it is recommended that you use an active probe, such as
an HP 85024A, and another spectrum analyzer. If an HP 1120A active probe
is being used with a spectrum analyzer having dc-coupled inputs, such as the
HP
8566A/B,
HP
8569A/B
and the HP
8562A/B,
either set the active probe
for an ac-coupled output or use a dc-blocking capacitor between the active
probe and the spectrum analyzer input.
Caution
n Do not short control voltages to ground. These voltages are not short-circuit
protected. DACs damaged by shorting these voltages might not fail until
several weeks after the shorting takes place.
w
Do not short power-supply voltages to ground. The HP 85623 spectrum
analyzer power-supply current limiting cannot protect the resistors in series
with the power supply.
Note
Some transistors have collectors connected to the case. Electrical connection
of the case to the collector might not be reliable, making collector voltage
measurements on the transistor case unreliable.
IF
Signature
1. Disconnect W27 (coax 3) from
A5J5.
2. Connect an SMB tee to
A5J5,
using a short coaxial cable with SMB connectors.
3. Connect one output of the tee to cable W27 (coax 3).
4. Connect an HP 85024A active probe, with a
1O:l
divider installed, to the other output of
the tee.
5. Connect the output (type N connector) of the active probe to the input of the
HP
8566A/B
spectrum analyzer.
6. Connect the probe power cable to the HP 85623 spectrum analyzer front-panel PROBE
POWER connector (you may need to use a probe power extension cable, HP 10131B).
7. Set the HP 8566A/B controls as follows:
Reference level
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+lO
dBm
Center frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 MHz
Span
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 Hz
Resolution bandwidth . .
..*.....................................
300
kHz
Videobandwidth
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300kHz
Sweep time
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..5.5s
Trigger
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single
8. On the HP
8566A/B,
p
ress
@K]
(trace A blank) to set detector to SAMPLE mode.
9. On the HP 85623 spectrum analyzer, press
[m)
and set the controls as follows:
9-22 IF Section