HP 8921A User Manual page 316

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Chapter 10, Signaling Encoder (AF Generator 2)
CDCSS Encoder
FM Coupling
Polarity
Send
316
This field alters the FM modulator to allow DCFM from internal and external
modulation sources. This field also selects ac or dc coupling between the RF
Generator's frequency modulator and the rear-panel MODULATION INPUT
connector.
Operating Considerations
This field should be set to
provides better modulation response at low data rates.
This setting determines the relationship between the data stream's logic levels and
the effect on the modulated signal.
This function is helpful to restore the proper data polarity when the transmitter,
repeater, or receiver used in your communications system has an odd number of
inversions; causing the received data to be inverted when decoded. (This is
common when a signal is translated to a lower frequency using an LO whose
frequency is higher than the signal's frequency; or when inverting amplifiers are
used.)
Normal Operation. When this field is set to
output level of the AF Generator to be more positive. A logical low (0) causes the
level to become negative by the same amount.
Inverted Operation. When this field is set to
the output level of the AF Generator to be more negative. A logical low (0) causes
the level to become positive by the same amount.
Selecting this field causes the data stream to be output.
whenever the
DC
AFGen2 To
Norm
Invert
field is set to
FM
, a logical high (1) causes the
, a logical high (1) causes
; this

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