Nautel FM10, Технические инструкции

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10 000 WATT FM BROADCAST TRANSMITTER
FM10
Page 6-10
15 November 1999
time the
POWER LOWER
switch (A13A1S9) is
momentarily pressed, a ground is applied to the Pwr
Decrease input (J2-41) and is detected by the counter
circuit. The counter circuit's total count will decrease
by one (until a minimum of '0' is reached
corresponding to no output power) and the
transmitter's output power will decrease by the
corresponding increment. If the
POWER LOWER
switch is pressed and held, after a brief pause the
transmitter's output power will decrease until the
POWER LOWER
switch is released or until no output
power has been reached.
6.5.2.7 Automatic Level Control (ALC): See
figure SD-9. The automatic level control circuit
operates internal to the control/monitor PWB and is
designed to prevent the transmitter output power
from being affected by changes in the load
impedance. A sample of the transmitter output
power is applied to
Fwd Pwr input (J9-1/2) of the
control/monitor PWB and is used as a reference for
the ALC circuit. Should the detected output power
sample differ from the forward power reference
signal, the ALC circuit will automatically adjust the
power level (
PA Volts Control ; J6-1/3) of the
transmitter. The activation of some protection
circuits will disable the ALC circuit.
6.5.2.8 Alarm Reset: See figure SD-9 and SD-
10. Alarm LEDs are latching and will remain turned
on even if the alarm condition is removed and the
transmitter's RF output has been restored. To reset
the alarm indications, the
ALARM RESET
switch must
be momentarily pressed. Alarm indications are
backed up by battery against AC power loss. When
AC power is restored, the last alarm indications on
the transmitter will still be activated. The
Alarm
Reset signal is active during turn on of the transmitter
to prevent false alarm indications.
6.5.2.9 Protection Reset: See figures SD-9 and
SD-10. Certain fault conditions in the transmitter
[
PA VDC/COMBINER MATCHING
alarm or
REFLECTED POWER
alarm (reflected power greater
than 300 watts and forward power very low)] will
cause the transmitter to shut down permanently. This
is accomplished by inhibiting (grounding) the
PA
Volts Control (J6-1/3) and the IPA Volts Control
(J8-12/11) outputs in response to a fault. Once the
fault has been removed/repaired, the shutdown
protection circuit must be reset manually by either
momentarily pressing the
PROTECTION RESET
switch (A13A1S7) or by applying a remote
PROTECTION RESET
command (TB1-5/6).
6.5.2.10 Module Inhibit Reset: See figures SD-9
and SD-10. A high temperature in an RF power
module or low RF drive level at its input will cause
15 VDC to be applied to one of the
PDM Inhibit ( A
thru F ) outputs and inhibit the output of the
corresponding switching power supply (A thru F).
Once the fault condition has been removed, the
associated module inhibit control signals must be
reset manually by momentarily pressing the
MODULE
RESET
switch (A13A1S3).
6.5.2.11 High RF Power Module Temperature:
See figures SD-9 and SD-10. The Temp (A) (J5-1)
thru Temp (F) (J5-6) inputs are DC voltages that are
inversely proportional to the temperature sensed by
thermistors in the RF power modules (A thru F).
These voltages are considered acceptable provided
they are greater than 5 VDC - corresponding to a
temperature of 85
°
C. If the temperature within an
RF power module exceeds 85
°
C, the associated Temp
input will drop below the 5 VDC threshold and cause
the associated
PDM Inhibit ( A thru F ) output to go
high, disabling the associated switching power
supply. At the same time, the ALC circuit is
disabled, the local
MODULE TEMP
indicator LED
turns on and the remote
HIGH TEMP
and
PA/MODULE
FAIL
alarms activate (current sink). A module inhibit
reset is required after the fault condition has been
removed/required.
6.5.2.12 High IPA Temperature: See figures SD-
9 and SD-10. The Temp (IPA) input (J1-2) is a DC
voltage inversely proportional to the temperature
sensed by a thermistor in the IPA module. This
voltage is acceptable if it is greater than 5 VDC -
corresponding to a temperature of 73
°
C. When the
temperature in the IPA module exceeds 73
°
C, the
IPA temperature sample voltage will drop below the
5 VDC threshold and cause the local
IPA TEMP
indicator LED to turn on and the remote
HIGH TEMP
and
IPA FAULT
alarms to activate (current sink).
6.5.2.13 Low RF Power Module RF Drive: See
figures SD-9 and SD-10. The Intermediate RF Level
( A thru F ) inputs (J5-7 thru J5-12) are DC voltages
that are proportional to the RF drive level applied to
the RF power modules (A thru F). These voltages
are considered to be acceptable provided they are