Nautel NX15, Руководство по эксплуатации и обслуживанию

Страница: 20 / 178

NX15/NX25 Operations and Maintenance Manual Description
Page 1-12 Issue 6.0 2019-01-31
Cutback:
A cutback occurs after multiple shutback events. When three shutback events occur within a
15 s period, the shutback accumulator exceeds its threshold. The transmitter responds by
limiting the output power to 85% of the previous power set point or the power at which the
shutback event occurred, whichever is lower. When multiple cutback events occur, the output
power is reduced by 85% of the current level after each event. The minimum cutback power
level is 25% of full carrier power. Further cutbacks will not decrease the power beyond this
point. When the transmitter is recovering from a cutback event, the accumulator must first
reach 0, which takes 60 s. After that, transmitter power is gradually restored to full power
according to the curve shown in Figure 1.4 .
Every SWR event that occurs is stressful to the RF amplifier; the more events that occur, the
more chances there are for a power module to fail due to an SWR event. The purpose of the
cutback routine is to decrease the voltage being applied to the RF amplifier when multiple
SWR events are occurring. Doing so decreases the stress on the RF amplifier during each event,
decreasing the probability of a power module failure.
Figure 1.4: Cutback Recovery Time