R.V.R. Elettronica TEX20-NV, Техническое руководство

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TEX20-NV Technical and Maintenance Manual
R.V.R. Elettronica S.r.l. (Bo) Pag. 16
CHAPTER 2
ELECTRICAL DESCRIPTION
2.1 INTRODUCTION
This section describes, in detail, the operating theory behind the TEX20-
N.V..
To aid understanding, the unit has been subdivided into blocks, each of which
is fully described below.
A Block Diagram is shown in Fig.3.
2.2 POWER SUPPLY
This circuit comprises a board, mounted on a heat sink, which is fixed
to the central part on the bottom of the unit (5 Foto 1-2).
The power supply generates the various stabilized voltages necessary for each
of the various modules that make up the TEX20-N.V..
After having undergone filtering for mains-borne interference, the supply is
transformed into lower voltages, rectified, smoothed and stabilized to the
following values: +12V, +15V and 2 to 24V variable (+20V upstream of the voltage
control stage).
The +15V supplies the EURO Audio Input card and the contraves card. The +12V
supplies the RF power amplifier driver and the 2-24V variable supplies the
final power stage of the same module.
The variable voltage of the final stage is controlled by the PWR ADJ control
which determines the RF power output of the exciter.
The automatic control of output power guarantees the power level set by the
PWR ADJ control right across the frequency range and independently of other
variables such as temperature, load variations etc.
The system works by comparing the value set by the PWR ADJ control with the
actual power output of the unit and compensating accordingly.
A power limiting circuit intervenes in the event of excess SWR on the output,
thus protecting the final stage.
2.3 EURO AUDIO INPUT CARD
This card (2 Foto 1-2) is situated on the front panel of the exciter.
This card, only for EUROPA version, filters all audio signal inputs to the
unit, removing R.F. interference, before supplying them to the main card.
This card works too as measures card allowing the measuring of forward and
reflected power or deviation.
2.4 MAIN CARD
The main card is situated internally, on left of the unit’s bottom (1 Foto
1-2).
The circuit includes a voltage-controlled oscillator (VCO) which generates