Comtech EF Data KST-2000L - Manual (Page 47)

Satellite Terminal System Revision 2
Operation MN/KST2000L.IOM
4.5.2 Fault and Error Response
Table 4-1 shows how the AGC system reacts to power outages, system faults and opera-
tion outside the specified limits.
Table 4-1. AGC Fault and Error Response
Problem Response/Notes
If the transceiver prime power fails The UCA value is effect prior to the failure is restored on power up.
If the input signal (70 or 140 MHz) is removed
or is set to
≤ –45dBm.
1. The internal Up Converter attenuator is set to its maximum value (mini-
mum gap).
2. The value of UCA is not affected.
3. The output power will slowly increase for several seconds until the gain
error reaches zero, when the input signal is reapplied.
If the user enters a value of UCA that is low for
a set input level. 1. The SSPA will be driven into saturation and the value of UCA will
automatically increase (Gain decreased) in steps of 1 dB until the SSPA
output power is below saturation.
2. The new (increased) value of UCA is displayed at the user’s interface.
Even if the input power is reduced, the new value of UCA will remain
fixed.
If the input power is increased, such that the
SSPA is driven into saturation. 1. The value of UCA is increased (Gain decreased) in steps of 1 dB until
the SSPA is below saturation.
2. The new value of UCA is displayed at the user’s interface. Even if the
input power is reduced, the new value of UCA will remain fixed.
Loop fault occurs when the Gain Error is non-
zero for >5 out 255 iterations of the processor
control loop. 1. A top level AGS_Fault is reported.
2. Excessive cable loss between the converter unit and the SSPA can cause
this condition.
3. If the AGC is enabled and the RF is commanded Off (
this fault is registered.
INSUFFICIENT INPUT POWER fault is gen-
erated when the IF input power transitions from
normal power to low power (< – 45 dBm). Under this condition, a top level AGS_fault is reported and the internal up
converter attenuator is set to its maximum value (minimum RF output). The
value of UCA is not affected. When the input signal increases above –45
dBm, the output power will slowly increase for several seconds until the gain
error reaches zero.
EXCESSIVE INPUT POWER fault is gener-
ated when the IF input power transitions from
normal power to high power (> –25 dBm). Under this condition, a top level AGS_Fault is reported. If the combination of
the input power and the up converter attenuator is such that the SSPA is
driven into saturation, the value of the UCA will automatically increase in
steps of 1 dB until the SSPA output power is below saturation. The new value
of UCA is displayed at the user’s interface. Even if the input power is re-
duced, the new values of UCA will remain fixed.
The LOOP, INSUFFICIENT INPUT POWER, and EXCESSIVE INPUT POWER faults can be displayed
by issuing the AGC current faults command ( . The allowed ranges of IF input power and
UCA settings are limited by the SSPA saturation and detector range to the shaded area defined in Figure 4-
6.
4–9