Comtech EF Data CDM-600/600L - Manual (Page 263)

CDM-600/600L Open Network Satellite Modem Revision 3
Appendix G MN/CDM600L.IOM
G–5
Any of these events opens the feedback loop preventing valid level correction. Once the stimulus
causing the loop to freeze is removed, the leveling loop will resume normal operation using the
previously established target tracking level.
A convenient way to verify that the leveling loop does indeed function is to first establish leveling
loop operation, then turn FSK OFF and change the modem transmit output power level, and
finally turn FSK back ON. Observe either the modem output power level in the CONFIG: TX Æ
POWER menu, or the monitored BUC output power level in the MONITOR: BUC menu. The
levels will incrementally change at 10-second intervals to bring the BUC output back to the target
tracking level.
Turning both BUC FSK and output power leveling ON inhibits capability to manually change the
modem transmit output carrier level since the leveling loop has control of the modem output.
When leveling is turned ON,
(ADJ) appears in the front panel display after the transmit power
level in the CONFIG: TX Æ POWER menu. Each time this menu is entered, the displayed
transmit output power level is updated with the current value set by the leveling loop.
BUC FSK related parameters, including leveling ON/OFF state and target tracking level, are
stored in nonvolatile memory like all other modem parameters that determine the set up state. If
FSK is turned ON, the modem M&C will set up FSK in the ON state if modem power is cycled
OFF/ON. Likewise, if leveling is ON and operating, the modem will reestablish the leveling
operation using the same target tracking level after a power cycle or after cycling the FSK state
OFF and then back ON.