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).
Parts
R1,R4,R14,R15 -10K 1/4W Resistor
R2,R3 -22K 1/4W Resistor
R5,R13 -3.9K 1/4W Resistor
R6,R11 -680 Ohm 1/4W Resistor
R7 -150 Ohm 1/4W Resistor
R8,R12 -100 Ohm 1/4W Resistor
R9 -68 Ohm 1/4W Resistor
R10 -6.8K 1/4W Resistor
C1 -4.7pF Ceramic Disc Capacitor
C2,C3,C4,C5,C7,C11,C12 -100nF Ceramic Disc Capacitor
C6,C9,C10 -10nF Ceramic Disc Capacitor
C8,C14 -60pF Trimmer Capacitor
C13 -82pF Ceramic Disc Capacitor
C15 -27pF Ceramic Disc Capacitor
C16 -22pF Ceramic Disc Capacitor
C17 -110uF 25V Electrolytic Capacitor
C18 - 33pF Ceramic Disc Capacitor
C19 -18pF Ceramic Disc Capacitor
C20 -12pF Ceramic Disc Capacitor
C21,C22,C23,C24 -40pF Trimmer Capacitor
C25 -5pF Ceramic Disc Capacitor
L1 -5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm
L2,L3,L5,L7,L9 -6-hole Ferroxcube Wide band HF Choke (5 WDG)
L4,L6,L8 -1.5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm
L10 -8 WDG, Dia 5 mm, 1 mm CuAg, Space 1 mm
D1 -BB405 BB102 or equal (most varicaps with C = 2-20 pF [approx.] will do)
Q1 -2N3866
Q2,Q4 -2N2219A
Q3 -BF115
Q5 -2N3553
U1 -7810 Regulator
MIC -Electret Microphone
MISC -PC Board, Wire For Antenna, Heatsinks
Notes:
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).
Parts
R1,R4,R14,R15 -10K 1/4W Resistor
R2,R3 -22K 1/4W Resistor
R5,R13 -3.9K 1/4W Resistor
R6,R11 -680 Ohm 1/4W Resistor
R7 -150 Ohm 1/4W Resistor
R8,R12 -100 Ohm 1/4W Resistor
R9 -68 Ohm 1/4W Resistor
R10 -6.8K 1/4W Resistor
C1 -4.7pF Ceramic Disc Capacitor
C2,C3,C4,C5,C7,C11,C12 -100nF Ceramic Disc Capacitor
C6,C9,C10 -10nF Ceramic Disc Capacitor
C8,C14 -60pF Trimmer Capacitor
C13 -82pF Ceramic Disc Capacitor
C15 -27pF Ceramic Disc Capacitor
C16 -22pF Ceramic Disc Capacitor
C17 -110uF 25V Electrolytic Capacitor
C18 - 33pF Ceramic Disc Capacitor
C19 -18pF Ceramic Disc Capacitor
C20 -12pF Ceramic Disc Capacitor
C21,C22,C23,C24 -40pF Trimmer Capacitor
C25 -5pF Ceramic Disc Capacitor
L1 -5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm
L2,L3,L5,L7,L9 -6-hole Ferroxcube Wide band HF Choke (5 WDG)
L4,L6,L8 -1.5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm
L10 -8 WDG, Dia 5 mm, 1 mm CuAg, Space 1 mm
D1 -BB405 BB102 or equal (most varicaps with C = 2-20 pF [approx.] will do)
Q1 -2N3866
Q2,Q4 -2N2219A
Q3 -BF115
Q5 -2N3553
U1 -7810 Regulator
MIC -Electret Microphone
MISC -PC Board, Wire For Antenna, Heatsinks
Notes:
- Email Rae XL Tkacik with questions, comments, etc.
- The circuit has been tested on a normal RF-testing breadboard (with one side copper). Make some connections between the two sides. Build the transmitter in a RF-proof casing, use good connectors and cable, make a shielding between the different stages, and be aware of all the other RF rules of building.
- Q1 and Q5 should be cooled with a heat sink. The case-pin of Q4 should be grounded.
- C24 is for the frequency adjustment. The other trimmers must be adjusted to maximum output power with minimum SWR and input current.
- Local laws in some states, provinces or countries may prohibit the operation of this transmitter. Check with the local authorities.
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