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S:\HP892XX\USRGUIDE\manual\encoscrn.fb
Chapter 10, Signaling Encoder (AF Generator 2)
CDCSS Encoder
FM Coupling
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 DC whenever the AFGen2 To field is set to FM; this
provides better modulation response at low data rates.
Polarity
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
Norm, a logical high (1) causes the
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
Invert, a logical high (1) causes
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.
Send
Selecting this field causes the data stream to be output.
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