Chapter 9 467
IF Section
A5 IF Assembly
3 kHz and 10 kHz Resolution Bandwidth Problems
Asymmetric Filter Response: Check the crystal symmetry control with
the following steps:
1. Press
PRESET.
2.Set the 8564EC or 8565EC spectrum analyzer controls as
follows:
Resolution bandwidth .................................................. 3kHz
Span .......................................................................... 100kHz
Center frequency ..................................................... 300MHz
3.On the 8564EC or 8565EC spectrum analyzer, connect the
300 MHz CAL OUTPUT to the INPUT 50Ω .
4. A trace similar to Figure 9-20, “Faulty Crystal Symmetry” indicates
a failed crystal-symmetry circuit.
Narrow 10 kHz resolution bandwidth: Check for printed-circuit board
contamination. Clean the board as required.
IF Gain Compression in 10 kHz resolution bandwidth: FET transistors
Q202, Q203, Q501, and Q503 can deteriorate with age. Measuring less
than 0 volts on the FET source indicates a bad FET.
Figure 9-20 Faulty Crystal Symmetry
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