Wednesday, August 31, 2011

RF Amplifier VHF FM 87.5- 108 MHz based MOSFET BLF245

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
Q1 = BLF245
R1,R3 = 5,6 Ohms
R2,R7 = 1,8Kohms
R4 = 6,8Kohms
R5,R6 = 10Kohms
R8,R9 = 12 Ohms
R10 = 220 Ohms
T2 = TRANSFO 2x500nH

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

Wednesday, August 24, 2011

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

Thursday, August 18, 2011

100W FM Amplifier Circuit using MRF317

electronic circuit diagram

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:

Sunday, August 14, 2011

2W VHF Linear Amplifier Circuit

electronic circuit diagram

These circuits may be utilised to amplify RF power signals, from 50MHz to 170MHz, just a couple of component modifications are necessary. The circuit diagram shown are "normalised" for 100MHz and will tune about 80MHz via to 120MHz. Simply scale the components up or down if you want to go down or up in frequency bands. The circuits as shown will give a acquire of about 14dB with an output power of about two Watts (input = 100mW). With an output power of 20 watts the acquire falls off to just 12dB at 100MHz or just 10dB at 170MHz.

L3 can be a massive RF choke, produced utilizing generally 20 turns of 22SWG wire in a ferrite ring. The wire have to be thick enough to carry the PA existing. For low powers a smaller ferrite is extra than sufficient. Do not scale this inductor for other frequencies.

L4 is created working with typically 3 or four turns of 22SWG enamelled wire inside a two ferrite beads side-by-side, as a pair of biniculars. For greater powers you should ideally use a bigger two-hole binocular ferrite core.

L2 is typically 4 turns of "thin" wire on a single ferrite bead for all frequency bands.

L1 and L5 are each close-wound 22SWG enamelled wire on an air-cored 5mm Dia. former. L1 and L5 need to physically be mounted as far away from one another as feasible and in a diverse plane (if one is vertical the other ought to be horizontal).

The 50pf and 75pf preset caps might be any old caps for low power work, but above about 1 watt you ought to choose high-power rated components.

The optional resistor within the emitter will restrict the maximum output power by reducing the gain of the complete amplifier. This resistor should be commonly 12 ohms for low power devices, which include the 2N3866 or 2N4427 devices. For BLW90 or other high-power devices the emitter resistor need to be a total short-circuit. In this event the power supply must also be protected having a fuse. In high-power circuits do not use relay switching or you might burn out relays. The circuit must not draw any important present with no signal. The 18 ohm resistor really should also be reduced for power devices, generally 5R6 for a 20W amplifier.

We have added TR2 to present the 0.7vDC bias inside the form of a basic series regulator. For driving modest transistors like the 2N3866 and 2N4427, TR2 can be a very simple BC547 or a 2N2222. For driving greater power amplifiers you must use a bigger transistor fitted having a heatsink. A 2N3053 or BCY51 device must be fine. Just before switching on the major DC power to the amplifier, set the bias potentiometer to minimum voltage, apply the power and adjust the pot until TR1 draws a bit present. For 500mW to 5 watt devices it is best to set TR1 current to about 5mA to 50mA. With five watt to 25W amplifiers you ought to set the TR1 existing to about 50mA to 200mA. Do not be to mean using the standing DC present as it truly is this that's keeping the FCC of your back by giving you a clean transmission (assuming you have got a license). Now you are able to align the complete Linear PA.

2W VHF linear amplifier circuit source:

Wednesday, August 3, 2011

5W RF Power Amplifier based 2SC2092 / MRF475

5W RF Power Amplifier based 2SC2092 / MRF475

Powered by special transistor designed for RF amplifier: 2SC2092 / MRF475, this RF power amplifier capable to deliver up to 5W signal output. 5W is a high power output for RF power amplifier circuit.

C5 and C8 are disc ceramic. C6 and C7 are tantalum or electrolytic. R1, R2 and R3 are 1/2W carbon composition resistors. Silver-mica capacitors may be substituted for polystyrene (P) types. Impedance transformation ratios are shown above T1 and T2.