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User Manual
Rev. 2.0 - 02/09/18
TEX30LCD/S
ELETTRONICA
7. Working Principles
7.1 Panel board
The panel board contains the microcontroller (PIC18F452) that implements the
equipment control software, the display and the other components needed to
interface with the user.
The board is connected with the other machine modules, both for power supply
distribution and for the control and measures.
7.2 Main board
The main board carries out the following functions:
•
Audio and SCA input treatment
•
Generation of carrier frequency
•
Modulation
•
R.F. amplification (Driver)
The board also features a stereophonic coder.
7.2.1 Audio input section
The audio input section contains the circuits that perform the following functions:
•
Input impedance selection
•
15 kHz filtering of the left and right channel
•
Stereophonic Coding
•
Mono channel preemphasis
•
Mono, MPX and SCA channel mixing
•
Clipper (limits the modulating signal level so that the frequency deviation does
not exceed 75 kHz)
•
Modulating signal measurement
7.2.2 PLL/VCO section
This board section generates the modulated radiofrequency signal. It is based on
a PLL scheme that uses an integrated MB15E06 type.
7.2.3 Driver section
Before passing to the final power amplifier, the RF signal is preamplified in this
section by an ERA3 transistor. When the exciter is placed on stand-by, the driver
is by-passed.
