500 WATT RADIOBEACON TRANSMITTER
ND2000A-02x-xx0
Page 2-2
15 January 2005
2.3.4
ALARM LAMPS:
The following
paragraphs explain each alarm lamp function:
2.3.4.1 Battery-Alarm
Lamp:
The
BATTERY-
ALARM
lamp is normally turned off. When the B-
operating voltage for the transmitter is produced by an
external dc power source (battery, etc.), a battery
control (+15 V dc) signal will be applied through
connector A1P4-1 and passed to the anode of
BATTERY-ALARM
lamp. The alarm-lamp will turn on.
2.3.4.2 RF Current-Alarm Lamp:
The
RF
CURRENT ALARM
lamp is normally turned off. When
the modulation level is too high, as sensed by the RF
current probe at the harmonic filter's input, +15 V dc
shall be applied through connector A1P5-12 to the
anode of the
RF CURRENT
lamp. The lamp will turn
on. The
RF CURRENT ALARM
lamp shall also turn on
if the antenna impedance is less than 50 ohms at the
sideband frequency and the antenna current is
exceeding the level expected under normal (50 ohm)
conditions.
2.3.4.3 SWR-Alarm
Lamp:
The
SWR-ALARM
lamp is normally turned off. When a reflected power
ratio in excess of 2:1 has been sensed at the output of
the harmonic filter, +15 V dc shall be applied through
connector A1P4-9 and passed to the anode of the
SWR-ALARM
lamp. The alarm-lamp will turn on.
2.3.4.4 Standby-Alarm
Lamp:
The
STANDBY
ALARM
lamp is normally off. When the selected main
side turns off (caused by a fault on the selected main-
side or a standby test control signal from a remote
location), a B- control signal will be applied through
connector A1P3-5 and passed to the
STANDBY-ALARM
lamp. The alarm-lamp will turn on.
2.3.4.5 Shutdown-Alarm
Lamp:
The
SHUTDOWN ALARM
lamp is normally turned off.
When the subject transmitter's main and standby sides
have turned off, a B- control signal will be applied
through connector A1P4-12 and passed to the cathode
of the
SHUTDOWN-ALARM
lamp. The alarm-lamp will
turn on. The
STANDBY-ALARM
lamp shall normally
be turned on prior to the
SHUTDOWN-ALARM
lamp
turning on.
2.3.5
SELECT MAIN TX SWITCHING:
The
SELECT MAIN TX
switch selects which side of the
subject transmitter will be the main operating side
A
or
B
. When set to
A
, the
A
side will be the selected
main-side and the
B
side will be the standby. Either
side may be selected for the main-side. The B-
operating voltage, from side
A
and side
B
of the
transmitter are interfaced through the selected contacts
of the switch and passed to their respective
destinations.
2.3.6
SWITCHED METERING:
The switched
metering circuit contains
a
TEST-Power/Mod
meter
with an associated switch and a
TEST-Volts/Current
meter with its associated switch. The following is a
description of the metering circuits:
2.3.6.1 Test-Power/Mod Meter/Switch:
The
TEST-Power/Mod
meter provides an indication of the
parameter (forward power, reflected power or
modulation) selected by the
TEST-Power/Mod
switch.
When it is set to
OFF
, the meter movement is shorted
out.
SET 100% MOD
potentiometer (located on the
monitor PWB) is adjusted for 100% modulation
indication on the meter when the switch is set to
MOD
SET
.
2.3.6.2 Test Volts/Current Meter/Test Switch:
The
TEST-Volts/Current
meter provides an indication
(for both sides of the transmitter) of the parameter (B-
Vdc, +24 V dc, +15 V dc, -15 V dc and dc current), as
selected by the
TEST-Volts/ Current
TEST
switch.
When it is set to
OFF
, the meter movement is shorted
out. Potentiometer A1A1R2 is adjusted for a precise
voltage indication on the meter when the switch is set
to
B-V
(Side
A
or Side
B
).
MODULATOR/POWER AMPLIFIER MODULE
2.4
There are two identical modulator/power
amplifier modules (A2 and A3) in the transmitter.
Only one of them will be in use during operation.
Modulator/power amplifier A2 will be selected when
the
SELECT MAIN TX
switch is set to
A
, modulator/
power amplifier A3 will be selected when it is set to
B
. See figure SD-4 for the electrical schematic and
figure MD-4 through MD-9 for assembly detail.
