Nautel VS300, Operation And Maintenance Manual

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VS300 Operations and Maintenance Manual Description
Page 1-4 Issue 8.0 2016-03-01
• provides local and remote interfacing for the transmitter. Local interfacing is performed via
the front panel display (U5) - a 4 x 20 character LCD display - and its adjacent keypad. The
UI contains a menu-based series of pages that serve specific functions. Similar interfacing, as
well as more advanced functionality, is available on a remotely accessed AUI.
Except for the RF drive signal, all signals going between the exciter, RF drive and RF power stages are
passed through the interface PWB (A3).
RF drive stage
See also electrical schematics Figure
SD-2
and
SD-4
.
The RF drive stage is comprised of exciter circuitry within the exciter/control PWB (A1) and the pre-
amp PWB (A4).
The pre-amp PWB accepts the low level RF Drive output from the exciter/control PWB (A1). Its RF
output is controlled by the Pre-Amp V input (set at +48 V) and Pre-Amp Bias output from the exciter/
control PWB (A1). The output of the pre-amp PWB (nominal 10 W) is applied to the RF power
stage’s PA PWB. Cooling air for the pre-amp PWB is provided by fan B1.
RF power stage
See also electrical schematics Figure
SD-2
and
SD-5
.
The RF power stage accepts the intermediate RF drive signal from the RF drive stage and generates
the final RF output. It consists of a PA (power amplifier) PWB (A5), a low pass filter PWB (A6), and
an output power probe (A7).
PA PWB
See Figure
SD-5
. The PA PWB (A5) is a push-pull RF power amplifier. It is capable of providing
100 W of RF power in the FM broadcast band (88 to 108 MHz). The RF output is controlled by the
PA V level generated by the power supply module, and the PA Bias output from the exciter/control
PWB (A1). Cooling air for the PA PWB is provided by fan B1.
Low pass filter PWB
See Figure
SD-2
. The low pass filter PWB (A6) accepts the output of the PA PWB and attenuates
harmonics before applying a filtered RF signal to the output power probe (A7).