40 Watt Amplifier For FM Broadcast

Pada Rangkaian ini menggunakan TR Mosfet tipe MRF171A,tegangan yang dikgunakan sebesar 28 Volt / 5 Amp power supply, untuk keamanan rangakaian ini disertakan pula SWR protection circuit yang berfungsi sebagai pelindung rangkaian RF jika terjadi ke-tidak cocokan (mismatch) antena yang langsung mematikan power suplly secara otomatis.

Penguat RF ini dapat di 'genjot' atau di Tune up sampai 57 Watts,untuk meng-drive-nya bisa menggunakan daya input sebesar 1 watts! . PERHATIAN gunakan ferrite beads dan capasitor feedthru rangkaian RF detector, kipas kontrol dan SWR protection circuits.

Lihat Skema Rangkaian  

Capacitor

Schematic Reference Value Description Package Supplier Supplier Part Number
C16 47 µF Electrolytic, 20%, 35V SMT or leaded Any Any
C9, C10, C13, C15 0.1 µF Ceramic, X5R, 50V 0805 SMT Digi-Key PCC1864CT-ND
C1, C3, C8, C12, C14 1000 pF Ceramic, 5%, NP0, 50V 0805 SMT Digi-Key PCC102CGCT-ND
C11 1000 pF Mica, 100V 2220 SMT Digi-Key 338-1008-ND
C17 1000 pF Ceramic Feed Thru Any Any
C20 300 pF Mica, 100V 1812 SMT Digi-Key 338-1026-ND
C6 100 pF Ceramic, 5%, NP0, 50V 0805 SMT Digi-Key PCC101CGCT-ND
C2 1.5 pF Ceramic, +/- 0.25 pF, NP0, 50V 0805 SMT Digi-Key PCC1R5CNCT-ND
C4, C5, C7 4.5 - 65 pF Plasitc dielectric trimmer Leaded Digi-Key SG3009-ND
C18 16 - 100 pF Mica compression trimmer Leaded Circuit Specialists 423
C19 25 - 150 pF Mica compression trimmer Leaded Circuit Specialists 424

Inductor

Schematic Reference Value Description Package Supplier Supplier Part Number
L1, L6, L7 700 Ohm @ 180 MHz Wide-band ferrite choke Leaded Digi-Key M2204-ND
L5 210 nH Air core Leaded Handwound Note 1
L2 64 nH, 5% Air core Leaded Coilcraft 132-05
L8 41 nH, 5% Air core Leaded Coilcraft 132-03
L3 25 nH, 5% Air core Leaded Coilcraft 132-01
L4 21 nH Air core Leaded Handwound Note 2

Resistor

Schematic Reference Value Description Package Supplier Supplier Part Number
R2 10,000 Ohms Cermet potentiometer, 1/2 Watt Leaded Digi-Key CT6P103-ND
R3 1800 Ohms Film, 1%, 1/2 Watt Leaded Digi-Key BC1.82KZCT-ND
R1 33 Ohms Film, 1%, 1/2 Watt Leaded Digi-Key BC33.2ZCT-ND
R4 10 Ohms Film, 5%, 2 Watt Leaded Digi-Key BC10W-2CT-ND

Dioda

Schematic Reference Value Description Package Supplier Supplier Part Number
D1, D2 1N4148 Silicon diode SMT or leaded Any Any
D3, D4 1N5232 5.6 Volt Zener diode, 500 mW Leaded Digi-Key 1N5232BDICT-ND
D5 1N5401 Silicon diode Leaded Digi-Key 1N5401GICT-ND

Transistor

Schematic Reference Value Description Package Supplier Supplier Part Number
Q1 MRF171A Motorola N-channel enhancement mode MOSFET Case style 211-07 Richardson Electronics MRF171A

Catatan

[1]  8 lilitan kawat 18 SWG enamelled copper wire pada diameter former 6.5 mm r, panjang lilitan12 mm
[2]  3 lilitan kawat 18 SWG tinned copper wire pada diameter former 4 mm, panjang lilitan 10 mm

 

Gambar

Select a picture for larger image.

[40watt-1]

Original Motorola Mostar 800 MHz RF power amplifier.

[40watt-5]

My version.

[40watt-2]

RF input match, bias tee and RF input detector.

[40watt-6]

The FET.  Drain to the right, sources grounded.

[40watt-4]

RF output match.  Here is starts getting cramped for space.  The RF output goes to the old 800 MHz low pass filter under the PC board.  The filter was isolated from the RF connector.

[40watt-9]

Alternate view of the RF input.

[40watt-10]

Alternate view of the RF output.

[40watt-7]

I cut the back of the radio off to use as a cover.

[40watt-8]

The heatsink is not adequate for this FET so it will require forced air cooling.