DB
ELETTRONICA TELECOMUNICAZIONI S.p.A.
PM 1000 – 1 kW FM Broadcasting Transmitter - U
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ANUAL
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4.
AMPLIFIER SECTION
4.1
GENERAL DESCRIPTION
The PM1000 amplifier stage is realised with a preamplifier/driver module (Fig. 4.2) and four 300 W
RF MOSFET amplifier modules (see
Fig. 12.1
). The input signal from the Sintel ‘96 is amplified to
about 24 W (through the AMP30 module) and then splitted (through a splitter board) in four equal
parts for driving the four AMP300 FM MOSFET amplifier modules. The output power of the four
AMP300 (about 250W) is then coupled (through a coupler board) and filtered by means of an
appropriate low pass filter.
At the output of the low pass filter there is a directional coupler for forward and reflected power
monitoring.
4.2
30 W PREAMPLIFIER/DRIVER STAGE
The amplifier stage is realized by the new 30W MOSFET amplifier board (DB 0110_010A). This
board is basically composed of four amplification WIDE BAND stages.
The first stage uses a BFQ19 transistor to amplify the input level. The second and the third
transistors are 2N4427. The last amplification stage uses a BLF245 MOSFET to obtain an output
RF power 30 W maximum.
The P3 trimmer (see Fig. 4.2) in the AMP30 board allows to adjust the mosfet bias current.
.An external panel trimmer and the P2 trimmer in the AMP30 board allows to adjust the
output power.
The AMP30 board is equipped with an initial 5-6 seconds delay to avoid accidental out of
band emissions in the initial PLL locking period.
Summary of Contents for PM 1000
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