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5. Log Amplifier
Adjustments
Reference
Related Performance
Tests
Note
Description
Equipment
Procedure
IF-Display Section
Scale Fidelity Test
The A4A3 Log Amplifier-Filter and A4A2 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.
First, the A4A2 Log Amplifier-Detector ZERO adjustment is checked
and adjusted if necessary, then the A4A3 Log Amplifier-Filter is set
for center frequency by injecting a signal and adjusting the bandpass
filter center adjustment for maximum DVM indication. The bandpass
filter amplitude is adjusted by monitoring the output of the filter
control line shorted and not shorted to the + 15V 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.
S P E C T R U M A N A L Y Z E R '$,,,
I
Figure 3-33. Log Amplifier Adjustments Setup
Digital Voltmeter (DVM) . . . . . . . . . . . . . . . . . . . . . . . . HP 3456A
Frequency Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . HP 3335A
1. Position instrument upright as shown in Figure 3-33, with top
cover removed.
2. Set LINE switch to ON and press
3. Key in
[
FREQUENCY SPAN
+ 10 dBm, [RESBW) 10 kHz, and press LIN
pushbutton.
5. Log Amplifier Adjustments
D I G I T A L V O L T M E T E R
(
INSTR PRESET
0 Hz,
)
FREQUENCY
S Y N T H E S I Z E R L E V E L
].
7.6 MHz,
]
Adjustments 3-65
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