Agilent Technologies 8590 Series Service Manual page 568

Softkey Descriptions
Softkey Descriptions
• While CAL: SPAN is displayed:
• FM DAC Error Check:
• Instruments equipped with Option 102, AM/FM
Speaker and TV Sync Trigger, display the message
CAL: FM GAIN + OFFSET. While CAL: FM GAIN +
OFFSET is displayed:
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The main-coil sweep sensitivity and span
attenuator are adjusted for LO spans greater
than 10 MHz.
The adjustment routine checks for three
displayed signals: 0 Hz, 300 MHz, and 600 MHz.
The test passes if all three signals are found
within a 750 MHz span.
The analyzer changes the center frequency
setting to move the displayed signal four
divisions.
If the signal moves within ±1.25 divisions of the
expected display position, the FM coil drive is
within tolerance.
The FM offset DAC is adjusted to position the
signal at center-screen. This calibrates the center
screen-position so that it represents an
unmodulated signal.
The top to bottom screen deviation of a
demodulated FM signal, referenced to center
screen, is calibrated for a specific frequency
deviation.
• A demodulated signal with a 100 kHz
frequency deviation is simulated using the
CAL OUT signal and a center frequency step
of 100 kHz.
• The center frequency is stepped up and the
FM gain is adjusted to position the signal at
top screen.
• The center frequency is stepped down and the
FM gain is adjusted to position the signal at
bottom-screen.
Chapter 13