HP 8924C Reference Manual page 265

FM Deviation
This field displays the measured FM deviation of the carrier being transmitted by
the mobile station. Four dashes (----) indicate that no carrier is present to measure.
See "Measure" in the HP-IB Command Syntax chapter of the HP 8924C
Condensed Programming Reference Guide for programming command syntax.
A numeric value would only be displayed in the connected state (that is, the
annunciator is lit). The
Connected
the field is set to
Display
Refer to the
"Display" field on page 223
measurement results from this field.
When the
CALL CONTROL
configured for optimal performance of the signaling decoder. Two characteristics
of the instrumentation which have a significant affect on the performance of the
signaling decoder are: 1) audio frequency gain and 2) post detection filtering.
While the
CALL CONTROL
fixed (that is, autoranging is tuned off). This is necessary to ensure that no
signaling bursts are missed as a result of the audio gain stages autoranging in
response to a burst of signaling data. Fixing the audio gain stages may result in a
slight accuracy degradation for FM deviation measurements less than 7 kHz.
In addition, the post detection bandwidth is set at <20 Hz and >99 kHz in the
Active, Register and Page states, and 300 Hz to 15 kHz when in the Connected
state. This is done to ensure that no signaling tones are filtered off. This wide post
detection bandwidth allows more noise to be introduced into the measurement
process which affects the measured deviation.
Given these conditions it is recommended that FM deviation measurements
requiring full Test Set FM deviation accuracy be made on the
screen or the
AF ANALYZER
autorange while on these screens and post detection filters can be selected to
optimize deviation measurements.
Screens Where Field is Present
CALL CONTROL
ANALOG MEAS
S:\hp8924c\REFGUIDE\MANUAL\fields.chp
Fields That Begin with the Letter F
FM Deviation
.
Meas
for information on how to read
screen is displayed, the Test Set's instrumentation is
screen is displayed the audio frequency gain stages are
screen. The audio frequency gains stages are set to
Chapter 4, Description of Fields
field is only displayed when
ANALOG MEAS
265