BEI Electronics LLC 7EPTX-AM5E ユーザーズマニュアル

4-7

4-21.

The modular design of the RF power modules allow the modules to be removed from the

transmitter for maintenance.  The remaining power modules will provide power to

maintain on-air operation.

4-22.

The PWM signal from the exciter circuit board is applied to the modulator circuit board.

The modulator circuit board is designed to amplify and convert the PWM signal to a dc

voltage which varies at an audio rate.  The output of the modulator circuit board is 

applied to the RF amplifier circuit boards.  Four indicator circuits monitor and display the

status of the:  1) PWM drive signal, 2) B+ dc supply, 3) modulator fault conditions, and 

4) blown fuse conditions.

4-23.

The RF amplifier circuit boards are designed with Class E amplifier technology and

MOSFET power transistors.  The circuit board operates from:  1) the varying dc voltage

from the modulator circuit board and 2) the RF drive signal from the exciter circuit board.

The RF drive signal from the exciter circuit board and the varying dc voltage from the

modulator are applied to a push-pull power MOSFET transistor amplifier circuit.  The

amplifier circuit is designed to output approximately 687.5 watts of RF power.  A fault

detection circuit monitors amplifier operation for fault conditions.

4-24.

RF COMBINER.

4-25.

Power from each RF amplifier circuit board is applied to a star combiner network.  The

combiner components are located on the rear panel of each power block.  The star 

combiner network consists of individual transformer and inductor networks for each

amplifier circuit board.  The combiner accepts RF power from each RF power module to

produce the rated RF output power.

4-26.

In addition to combining the RF power from the RF power modules, the combiner design

allows one or more RF power modules to be removed from the transmitter for 

maintenance.  The remaining RF power modules will continue to operate to maintain

on-air operation.  This is accomplished without the use of dummy modules or bypass

switches.

4-27.

OUTPUT NETWORK.

4-28.

The output network is a modular assembly designed to match the transmitter impedance

to the antenna.  The assembly consists of a:  1) bandpass filter, 2) directional coupler

circuit board, 3) T-matching network, 4) lightning protection circuit board, and 5) a

lightning detection circuit board.

4-29.

The bandpass filter is an eight element LC filter designed to attenuate all harmonic

frequencies to FCC, DOC, and CCIR levels.  The directional coupler circuit board consists

of a circuit designed to sample the transmitter RF output.  The circuit board generates

both forward and reflected power samples for application to the controller circuit board.

The T" matching network consists of an LC network.  The network is designed to match

the transmitter impedance to the antenna.

4-30.

A lightning protection circuit board is provided to protect the transmitter circuitry from

direct lightning potentials.  The circuit protects the transmitter by shunting lightning

potentials to ground.  The lightning detector circuit board is designed to mute the

transmitter RF output during the presence of a lightning potential.  The lightning 

detector circuit board is controlled by a spark gap.  The circuit will respond to potentials 

of 1500 volts in AM-2.5E models and 2100 volts in AM-5E models.  This prevents the

transmitter from muting during near-by lightning activity.