HP 8360 - Manual (Page 214)

Coupling
Programming Codes SCPI: FM:FILTer:HPASs
<num> sets the AC bandwidth to 100 for any value 1
and sets the AC bandwidth to 20 Hz for any value 1
Analyzer: NONE
[MOD], also see “FM” and “Modulation”.
FM Coupling DC
Function Group
Menu Map
Description This (Option 002 only) lets you set the FM input to be
DC-coupled. Use DC coupling for modulation rates below 100
In this mode, the phase-locked loop is de-activated. This means that
the synthesizer is operating as an open loop sweeper. The synthesizer
will not be phase locked, and therefore, be aware that the phase noise
and CW frequency accuracy specifications do not apply.
An asterisk next to the key label indicates that DC FM coupling is
selected. The factory preset default is AC coupling.
For synthesizers Option 002, see FM On/Off DC.
Programming Codes SCPI: FM:FILTer:HPASs <num>[freq
Analyzer: NONE
also see “FM” and “Modulation”.
Operating and Programming Reference HP 8360
User’s Handbook