3 Watt FM Transmitter

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Rae XL Tkacik 48,725 12 58
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,R15410K 1/4W Resistor
R2,R3222K 1/4W Resistor
R5,R1323.9K 1/4W Resistor
R6,R112680 Ohm 1/4W Resistor
R71150 Ohm 1/4W Resistor
R8,R122100 Ohm 1/4W Resistor
R9168 Ohm 1/4W Resistor
R1016.8K 1/4W Resistor
C114.7pF Ceramic Disc Capacitor
C2,C3,C4,C5,C7,C11,C127100nF Ceramic Disc Capacitor
C6,C9,C10310nF Ceramic Disc Capacitor
C8,C14260pF Trimmer Capacitor
C13182pF Ceramic Disc Capacitor
C15127pF Ceramic Disc Capacitor
C16122pF Ceramic Disc Capacitor
C17110uF 25V Electrolytic Capacitor
C18133pF Ceramic Disc Capacitor
C19118pF Ceramic Disc Capacitor
C20112pF Ceramic Disc Capacitor
C21,C22,C23,C24440pF Trimmer Capacitor
C2515pF Ceramic Disc Capacitor
L115 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm
L2,L3,L5,L7,L956-hole Ferroxcube Wide band HF Choke (5 WDG)
L4,L6,L831.5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm
L1018 WDG, Dia 5 mm, 1 mm CuAg, Space 1 mm
D11BB405BB102 or equal (most varicaps with C = 2-20 pF [approx.] will do)
Q112N3866
Q2,Q422N2219A
Q31BF115
Q512N3553
U117810 Regulator
MIC1Electret Microphone
MISC1PC Board, Wire For Antenna, Heatsinks

Notes

  1. Email Rae XL Tkacik 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.

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Comments

freab demissie
fm trasmitter that covers 1km square
Monday, March 17, 2008 8:59:12 AM
it helps me to the final project .so that i want schematic diagram and discription of each components and ratings.
Dumidan
3 Watt FM Transmitter
Tuesday, March 11, 2008 4:44:29 AM
U1 7810 = LM 7810 or equivalent voltage regulator, out=10V
Shelton
3 Watt FM Transmitter
Saturday, March 08, 2008 7:11:39 AM
I think you can change the frequency of transmission by adjusting C14. Regards
George
3 Watt FM Transmitter HELP....
Saturday, March 01, 2008 12:55:17 AM
The circuit seems very useful.But it will be very helpful if you clarify my following things 1. What is its working range or how to set the frequency range. 2.Will it depend on the antenna height. 3.What is the use of 7810 Regulator.
JASEEM
3 Watt FM Transmitter
Saturday, March 01, 2008 12:40:40 AM
1.WILL YOU TELL ME ABOUT "U1 7810 REGUTATOR". USE AND OPERATION 2.WHAT WILL BE THE RANGE ? 3.HOW TO SET THE FREQUENCY? THANK YOU
Dipen Sen
3 Watt FM Transmitter
Friday, February 22, 2008 9:17:57 AM
i want to know the range of this transmitter.
v.vinoth
3 Watt FM Transmitter
Thursday, February 21, 2008 5:32:05 AM
it will be allowed are not for project and how long distance it will work?
hellbend
100 Watts FM Transmitter
Tuesday, February 19, 2008 1:48:15 PM
i want to build a 100 watts or greater transmitter, what i'm trying to do is to learn how to build a land mobile radio, mostly like the ones made by Midland or Vertex, is there anyone that can direct me to any informations. thank you
OMAR HAMIDU HASSAN
3 Watt FM Transmitter
Wednesday, February 13, 2008 5:15:01 PM
I wish to build 3 Watt FM Transmitter as my project, please guide me on the schematic diagram and send more detail in respect of the circuit diagram through my email omarhassan2323@yahoo.com
Gan
FM Transmitter
Tuesday, January 29, 2008 7:26:13 AM
can you send to me FM Transmitter schematic and proposal to me as fast as possible.thx.....
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