Broadcast Electronics AM-2.5E, Руководство пользователя

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4-2
4-12. The exciter circuit board generates: 1) a PWM (pulse-width-modulation) signal and 2) an
RF carrier frequency signal. The 122 kHz to 135 kHz PWM signal is routed for
application to the modulator circuit boards in the RF power modules. The RF carrier
frequency signal is applied to the power amplifier circuit boards in the RF power modules.
The exciter carrier frequency is established by a digital frequency synthesizer. The
synthesizer is a phase-locked-loop circuit which provides extremely accurate and reliable
carrier frequency operation.
4-13.
CONTROLLER CIRCUIT BOARD.
All transmitter control operations are directed by the
ECU controller circuit board. The controller circuit board is designed with CMOS control
and monitoring circuitry.
4-14. The controller circuit board is designed with two interlock circuits. A transmitter
external interlock is provided such as for a test load. An antenna interlock circuit is
provided to prevent the transmitter from operating into an incorrect antenna.
4-15. The transmitter power is controlled by a power control circuit. The circuit allows the
transmitter to be operated at five power levels. A power trim circuit allows the
transmitter power to be increased or decreased as required. A high reflected power
detection circuit, a high forward power detection circuit, and a high temperature
detection circuit operate in association with the power control circuit to foldback the
transmitter power during high reflected power, high forward power, and high
temperature conditions. In addition, a lightning detector circuit is provided to mute the
transmitter when lightning is present at the antenna.
4-16. Several monitoring and display circuits provide information on transmitter operating
conditions. An RF power module status circuit displays: 1) if a module is removed for
maintenance or 2) if a power module fault has occurred. A power supply status circuit
displays: 1) if a power supply circuit board is removed for maintenance or 2) if a power
supply fault has occurred. An exciter status circuit indicates if a fault has occurred in the
exciter. An antenna status circuit displays: 1) 1.2 : 1 VSWR conditions, 2) high reflected
power conditions, and 3) emergency reflected power conditions.
4-17. Additional display circuits include: 1) remote, 2) conflict, 3) lightning, 4) interlock,
5) over-temperature, and 6) reset. A remote indicator displays the status of the remote
control system. A conflict indicator illuminates to indicate an incorrect power level is
selected for operation into an antenna. A lightning indicator illuminates to indicate the
presence of lightning at the transmitter output. An interlock indicator displays the status
of the internal and external interlock. An over-temperature indicator illuminates to
indicate a transmitter temperature greater than 70 degrees C. A reset indicator
illuminates to indicate a transmitter fault has occurred. Transmitter faults include:
1) exciter failure, 2) power supply failure, 3) RF power module failure, 4) high reflected
power conditions, 5) reflected power emergency conditions, 6) over-temperature
conditions, 7) lightning conditions, and 8) 1.2:1 VSWR conditions.
4-18.
POWER SUPPLY.
DC operating potentials for the ECU assembly is provided by a modular
switching power supply unit. The unit pr5V, +15V, and -15V dc operating
potentials for the ECU circuit boards. +5V, +15V, and -15V indicators are provided on the
exciter circuit board.
4-19.
RF POWER MODULE.
4-20. An RF power module is a plug-in assembly containing two RF amplifier circuit boards
and a modulator circuit board. Each RF power module is designed to produce 1375 watts
of RF power. Two RF power modules are contained in a power block. The AM-2.5E
transmitter is equipped with 1 power block. The AM-5E transmitter is equipped with 2
power blocks.