RF Amplifier VHF FM 87.5- 108 MHz based MOSFET BLF245

This is the RF amplifier for VHF/FM range frequency of 87.5- 108 MHz. The circuit built using power transistor MOSFET BLF245.

The achievement of this 30W RF amplifier was designed to take place on a heatsink microprocessor PC. Equipped with its fans, the advantage of this method of cooling was chosen for the fact it is common and not very expensive. The size of the circuit will adapt quite easily to the type of sink that you have available, nine if possible, because often, those of recovery, the fans have already lived and the price of a new model remains very affordable.

Parts List:

C1,C4 = 47nF50v
C2,C8 = 4,7uF63v
C3,C5 = 22nF50v
C6,C7 = 1nF50v
C9 = 100nF50v
C10,C15 = 2,2nF
C11 = 27pF
C12,C18 = 82pF
C13 = 120pF
C14 = 8,2pF
C16 = 22pF
C17 = 47pF
D1,D2 = ZENER 3,9v
L1 = 2,4uH
L2 = 360nH
L3,L4,L5 = STRIP-LINE
Q1 = BLF245
R1,R3 = 5,6 Ohms
R2,R7 = 1,8Kohms
R4 = 6,8Kohms
R5,R6 = 10Kohms
R8,R9 = 12 Ohms
R10 = 220 Ohms
T1 = TRANSFO COAXIAL
T2 = TRANSFO 2x500nH

Visis this page for detailed explanation and tutorial of the RF amplifier circuit.

40Mhz RF Amplifier Circuit

This is the 40Mhz RF amplifier circuit. The sensitivity of a receiver may be significantly increased if this circuit is inserted between the receiver and the antenna. The amplifier circuit does not use resonant circuits and is suitable for both medium and for the short waves, up to 40 MHz.

The gain of this RF amplifier is 20db and it consumes 7mA electric current, when it is supplied with 12 until 15V dc. The input and the output should be connected with coaxial cable, resistance 75ohm.

Parts List:

R1 = 75ohm R2 = 10Kohm R3-7 = 5.6Kohm R4-5 = 4.7Kohm R6 = 820ohm R8 = 470ohm R9 = 2.2Kohm R10 = 68ohm

C1-3 = 47nF/100V C2-4 = 10nF/100V C5-6 = 47nF/100V Q1-2-3 = AF125 J1-2 = Jack BNC

100W FM Amplifier Circuit using MRF317

This FM power amplifier is build using a bipolar transistor MRF317. Similar to a lots of FM amplifier application, the power transistor is in a C class bias.

All the impedance networks (Input & Output) have been determined by using the Mimp software. A 9 elements low pass filter ensures that we meet at least a 60 dB rejection from the carrier (RF Simulation with RFSIM99). The FM RF amplifier has a 10 dB gain with a 60 to 65% efficiency. The Input VSWR is around 1.4 and there's no problem to reach the maximum power in all the FM band.

100W FM Amplifier Circuit source: radioinitiation.chez-alice.fr