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To check the gains for the IF assemblies
The overall gain of individual assemblies in the IF section are listed
below. The gain level provided for the A12 assembly is correct only
when the analyzer is set as provided in step three, above.
• The A11 bandwidth filter assembly produces 10 dB of gain.
• The A12 amplitude control assembly produces 5 dB of gain.
• The A13 bandwidth filter assembly produces 10 dB of gain.
• A +10 dBm signal at the input of the A14 log amplifier assembly
produces a 2 volt signal (VIDEO_IF) that is equivalent to a
top-screen display.
Refer to "IF Section Information" in
Analyzer"
for the changes in gain output when the instrument settings
are changed from the settings used in this section.
To measure the IF signal from the A9 third
converter
Measure the 21.4 MHz IF output from the A9 assembly with the
following procedure. Refer to the IF/Control Overall Block Diagram,
while performing this procedure.
1. Remove the A11 bandwidth filter assembly.
2. Insert the IF test board in the A11 assembly slot.
3. Measure the 21.4 MHz IF output at J1 on the IF test board using an
active probe, with an analyzer attached. (Use of a 50 Ω analyzer will
cause erroneous power-level measurements.)
4. The test limit for the 21.4 MHz IF signal is −45 dBm ±2 dB. The test
board receives the signal at measurement point A on the block
diagram.
Note that the variable IF amplifier at the output of the A9 assembly has
a gain range of −15 to +2 dB. This level is dependent on the output from
the reference level DAC, located on the A7 analog interface assembly,
that is adjusted during the
Chapter 5
Chapter 4, "Troubleshooting the
self-calibration routine.
CAL AMPTD
Troubleshooting the IF Section
IF Power-Level Measurement
257
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Table of Contents
Troubleshooting
