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Chapter 8, Programming the Call Processing Subsystem
Programming the CALL CONTROL Screen
FM Deviation
This field displays the measured FM deviation of the RF carrier being transmitted
by the mobile station on the reverse voice channel. Four dashes (----) indicate that
no carrier is present to measure.
A numeric value would only be displayed in the connected state (that is, the
Connected annunciator is lit). The FM Deviation field is only displayed when
the
Display field is set to Meas.
Refer to the
Display field description, on page 444, for information on how to
read measurement results from this field.
NOTE: When the CALL CONTROL screen is displayed, the Test Set’s instrumentation is
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 screen is displayed the audio frequency gain stages
are 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 ANALOG MEAS
screen or the AF ANALYZER screen. The audio frequency gains stages are set to
autorange while on these screens and post detection filters can be selected to
optimize deviation measurements.