dB PM 1000 User Manual
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Contents
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DB ELETTRONICA TELECOMUNICAZIONI S.p.A.PM 1000 – 1 kW FM Broadcasting Transmitter - U SER ’ S M ANUAL 21 /1014. AMPLIFIER SECTION4.1 GENERAL DESCRIPTIONThe PM1000 amplifier stage is realised with a preamplifier/driver module (Fig. 4.2) and four 300 WRF MOSFET amplifier modules (see Fig. 12.1). The input signal from the Sintel ‘96 is amplified toabout 24 W (through the AMP30 module) and then splitted (through a splitter board) in four equalparts for driving the four AMP300 FM MOSFET amplifier modules. The output power of the fourAMP300 (about 250W) is then coupled (through a coupler board) and filtered by means of anappropriate low pass filter.At the output of the low pass filter there is a directional coupler for forward and reflected powermonitoring.4.2 30 W PREAMPLIFIER/DRIVER STAGEThe amplifier stage is realized by the new 30W MOSFET amplifier board (DB 0110_010A). Thisboard 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 thirdtransistors are 2N4427. The last amplification stage uses a BLF245 MOSFET to obtain an outputRF 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 theoutput power.The AMP30 board is equipped with an initial 5-6 seconds delay to avoid accidental out ofband emissions in the initial PLL locking period. |
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