Bird Technologies ACMI - Manual (Page 16)

4

No alarm is activated if the VSWR is less than the maximum, or if the
VSWR alarm is disabled.

If the VSWR is equal to or slightly greater than the maximum, additional
measurements are accumulated to determine a trend. If reverse power is
increasing, an alarm is triggered. If the reverse power is stable, measure-
ments continue until a trend is established. An alarm will be triggered if the
VSWR exceeds the maximum for more than thirty seconds.

If the VSWR is much greater than the maximum then an alarm condi-
tion is triggered immediately.
Alarm on Zero Power
When the forward power is very small (< 2.5% of full scale), the measured VSWR
becomes large due to the noise floor of the sensor. Under these conditions, the
VSWR level is meaningless. When the zero power alarm is disabled, the VSWR will
not be monitored at these low powers.
High Power Alarm
When the high power alarm is enabled, the forward power is continuously moni-
tored. The alarm trigger is a percentage of the Monitor’s full scale power, from 0 –
125%. If the forward power is greater than the trigger level, an alarm is triggered.
Low Power Alarm
When the low power alarm is enabled, the forward power is continuously moni-
tored. The alarm trigger is a percentage of the Monitor’s full scale power, from
0 – 125%. If the forward power is less than the trigger level, an alarm is trig-
gered.
Push-to-Talk
The low power alarm and the VSWR alarm can falsely trigger when the transmit-
ter is not keyed. The Push-to-Talk feature disables alarm checking for a predeter-
mined period after the Push-to-Talk logic line is asserted. In order to prevent false
alarms while monitoring for low power and high VSWR, the Push-to-Talk feature
must be enabled.