FM Antenna Amplifier Circuit

  
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With this technique, an extra cable to power the fm antenna amplifier is unnecessary. The RF signal and the DC current supplying the amplifier use the cable simultaneously. Check another FM antenna booster circuit diagram. The RF signal is however prevented by LC filters from flowing into the power supply. The amplifier works with either 50 ohm or 75 ohm
FM Antenna Amplifier Circuit - schematic

antenna. It has a gain of 25 30 dB. MOSFETs are used to avoid the problem of crossmodulation or intermodulation. The circuit is divided into two parts. The first part is the active aplifier circuit which is normally installed very near the antenna. The second part is the power supply circuit which supplies current to the amplifier through the coax cable. After the fm antenna amplifier circuit is constructed, the power supply should be connected to it. You must then test the DC voltage in the cable. This must be between 15. 5 and 36. 6 volts. Then test the voltage between T5 collector and ground while adjusting the supply voltage. It must move from 3 to 24 volts. The emitter of T2 should be approx. 11. 4 volts. If the voltage at R4 is between 0. 7 and 2 volts, then the MOSFET is functioning properly.



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