HP 8568B, Performance Tests And Adjustments Manual, Page: 179 / 313

5. Log Amplifier Adjustments
5. Log Amplifier
Adjustments
Reference
Related Performance
Tests
Note
IF-Display Section
Log Amplifier-Filter
Log Amplifier-Detector
Scale Fidelity Test
The Log Amplifier-Filter and Log Amplifier Detector
are temperature compensated as a matched set at the factory. In
the event of a circuit failure, a new matched set must be ordered.
Contact your nearest HP Service Center.
Description
First, the Log Amplifier-Detector ZERO adjustment is checked
and adjusted if necessary, then the Log Amplifier-Filter is set
for center frequency by injecting a signal and adjusting the
filter center adjustment for maximum DVM indication. The
filter amplitude is adjusted by monitoring the output of the filter
control line shorted and not shorted to the +
supply. Next, log
fidelity (gain and offset of the log curve) is adjusted by adjusting the
-12 VTV and the PIN diode attenuator. Last, the linear gain step
adjustments are performed to set the proper amount of step gain in
the linear mode of operation.
Equipment
Procedure
S P E C T R U M A N A L Y Z E R
I
D I G I T A L V O L T M E T E R
S Y N T H E S I Z E R L E V E L
Figure 3-33. Log Amplifier Adjustments Setup
Digital Voltmeter (DVM) . . . . . . . . . . . . . . . . . . . . . . . . HP
Frequency Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . HP
1. Position instrument upright as shown in Figure 3-33, with top
cover removed.
2. Set LINE switch to ON and press
(
INSTR PRESET
].
3. Key in
[
FREQUENCY SPAN
)
0 Hz,
FREQUENCY
]
7.6 MHz,
+ 10 10 and press LIN
pushbutton.
Adjustments 3-65