3-3.5 Watt FM Transmitter


This is the schematic for an FM transmitter with 3 to 3.5 W output
power that can be used between 90 and 110 MHz. Although the stability
isn’t so bad, a PLL can be used on this circuit.

This is a circuit that I’ve build a few years ago for a friend, who
used it in combination with the BLY88 amplifier to obtain 20 W output
power. From the notes that I made at the original schematic, it worked
fine with a SWR of 1 : 1.05 (quite normal at my place with my antenna).

 

Schematic

This is the schematic of the 3W FM Transmitter

 

Parts:


Part

Total Qty.

Description

Substitutions
R1,R4,R14,R15 4 10K 1/4W Resistor  
R2,R3 2 22K 1/4W Resistor  
R5,R13 2 3.9K 1/4W Resistor  
R6,R11 2 680 Ohm 1/4W Resistor  
R7 1 150 Ohm 1/4W Resistor  
R8,R12 2 100 Ohm 1/4W Resistor  
R9 1 68 Ohm 1/4W Resistor  
R10 1 6.8K 1/4W Resistor  
C1 1 4.7pF Ceramic Disc Capacitor  
C2,C3,C4,C5,C7,C11,C12 7 100nF Ceramic Disc Capacitor  
C6,C9,C10 3 10nF Ceramic Disc Capacitor  
C8,C14 2 60pF Trimmer Capacitor  
C13 1 82pF Ceramic Disc Capacitor  
C15 1 27pF Ceramic Disc Capacitor  
C16 1 22pF Ceramic Disc Capacitor  
C17 1 10uF 25V Electrolytic Capacitor  
C18 1 33pF Ceramic Disc Capacitor  
C19 1 18pF Ceramic Disc Capacitor  
C20 1 12pF Ceramic Disc Capacitor  
C21,C22,C23,C24 4 40pF Trimmer Capacitor  
C25 1 5pF Ceramic Disc Capacitor  
L1 1 5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm  
L2,L3,L5,L7,L9 5 6-hole Ferroxcube Wide band HF Choke (5 WDG)  
L4,L6,L8 3 1.5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm  
L10 1 8 WDG, Dia 5 mm, 1 mm CuAg, Space 1 mm  
D1 1 BB405 BB102 or equal (most varicaps with C = 2-20 pF [approx.] will do)
Q1 1 2N3866  
Q2,Q4 2 2N2219A  
Q3 1 BF115  
Q5 1 2N3553  
U1 1 7810 Regulator  
MIC 1 Electret Microphone  
MISC 1 PC Board, Wire For Antenna, Heatsinks  

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