Nautel XL12, Technical Instructions

Page: 32 / 238

12 000 WATT AM BROADCAST TRANSMITTER
XL12
Page 2-8
01 January 2002
2.1.11 REMOTE ALARM INDICATIONS:
Outputs that indicate stress thresholds for critical
parameters have been exceeded are available on
terminals of the remote interface PWB. A switching
device for each alarm output provides a negative
logic (current-sink-to-ground) output when an alarm
condition exists. There are two options available for
the non-alarm condition. Alarm outputs are
protected against transients and/or over voltage by
39 volt zener diodes.
Option 1:
The switching circuit provides an open
collector during normal operation (non-alarm
condition) and has no influence on the external
monitoring circuit. For this option, resistor arrays
U11 thru U14 are not installed on the remote
interface PWB and each monitoring circuit must
present an impedance, between the switching device
and a positive DC voltage source, that will result in a
current flow of not more than 50 milliamperes. If
desired, +24 VDC is available for use by the remote
monitoring circuits from TB1-26 (
+24V INTLK ) of the
remote interface PWB. If an external DC power
source is used, it must not 24 VDC and its
return must be connected to TB1-27 (
GND
) on the
remote interface PWB.
Option 2:
The switching circuits provide a TTL
compatible output. +5 VDC is applied to the alarm
output terminal as the logic '0' state (non-alarm
condition) and a current sink to ground is applied as
the logic '1' state (alarm condition). For this option,
resistor arrays U11 thru U14 must be installed on the
remote interface PWB and the DC return for the
monitor circuits must be connected to TB1-27 (
GND )
on the remote interface PWB.
2.1.11.1 RF Stress Current Alarm:
An alarm
output that indicates the RF output is being cutback,
because the RF output current is exceeding the
maximum current the RF power modules can
provide, is available on TB2-24 (
RF OVER CURRENT ).
A negative logic output (current-sink-to-ground) will
be present for an alarm condition.
2.1.11.2 Filter Over Temp Alarm:
An alarm
output that indicates the RF output is being inhibited,
because the ambient air temperature in the RF output
filter is in excess of 85
°
C, is available on TB2-22
( FILTER OVER TEMP ). A negative logic output
(current-sink-to-ground) will be present for an alarm
condition.
2.1.11.3 High Reflected Power Alarm:
An
alarm output that indicates the peak reflected power
is exceeding or has exceeded 2000 watts is available
on TB2-26 (
HIGH VSWR ). A negative logic output
(current-sink-to-ground) will be present for an alarm
condition.
2.1.11.4 RF Power Cutback Alarm:
An alarm
output that indicates the RF carrier level has been
automatically reduced (cut back) to a level that will
not exceed the stress current threshold of the RF
power amplifiers. Cutback occurs when the RF
output is momentarily shut back (turned off) more
than three times in any five second period because
an RF related stress threshold was exceeded. This
output is available on TB2-27 (
RF PWR CUTBACK ). A
negative logic output (current-sink-to-ground) will be
present for an alarm condition.
2.1.11.5 RF Inhibit Alarm:
An alarm output that
indicates the RF output is being inhibited, because an
active external RF inhibit command is being applied
to the
PDM INHIBIT terminals (TB2-5 or TB2-6), is
available on TB3-1 ( INHIBIT PDM EXT ). A negative
logic output (current-sink-to-ground) will be present
for an alarm condition.
2.1.11.6 Standby Exciter Alarm:
An alarm
output that indicates an automatic exciter changeover
has occurred and the reserve (standby) exciter is
enabled as the pulse duration modulation (PDM)/RF
drive source, is available on TB3-2 (
STANDBY ). A
negative logic output (current-sink-to-ground) will be
present for an alarm condition.
2.1.11.7 Modulation Protection Alarm:
An
alarm output that indicates the modulating audio's
positive peaks are being limited; because their
amplitude and/or low frequency duration would
require RF currents that exceed the RF amplifier's
stress current threshold, is available on TB3-3
(
MODULATOR PROTECTION
). A negative logic output
(current-sink-to-ground) will be present for an alarm
condition.
2.1.11.8 Power Module Fault Alarm:
An alarm
output that indicates the RF output has been reduced,
because one more RF power modules have been
turned off and are not contributing to the RF output,
is available on TB3-4 (
PM FAULT
). A negative logic
output (current-sink-to-ground) will be present for an
alarm condition.