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
10uF 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:
1. Email Rae XL Tkacik (vocko@atlas.cz) with questions, comments, etc.
2. 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.
3. Q1 and Q5 should be cooled with a heat sink. The case-pin of Q4 should be grounded.
4. C24 is for the frequency adjustment. The other trimmers must be adjusted to maximum output power with minimum SWR and input current.
5. Local laws in some states, provinces or countries may prohibit the operation of this transmitter. Check with the local authorities.
Source: Electronics Lab
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