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Portable 1 Watt PLL FM Transmitter (88-108 MHz) Circuit

A neat little FM transmitter with PLL (Phase Locked Loop) control. Includes schematics, component lists and Printed-Circuit-Board (PCB) designs.

Screenshot: Portable 1 Watt PLL FM Transmitter (88-108 MHz) Circuit

The circuit diagram is divided into 3 separate sections: the RF part, the PLL (Phase Locked Loop) control circuit and the Audio and Power Supply circuit. Each circuit diagram includes a full parts/component list.

The page also includes a PCB design, so you won't need to worry about making the circuit on a verobroard (strip-board), which would obviously be a negative on circuit performance anyway! Instructions on how to tune the RF circuit are included, and the circuit does seem to be OK, so it should be easy enough to get this transmitter on-air.

Quoted Technical Specifications:
  • Supply voltage: 12 V from accumulator or regulated power supply
  • Supply current (HI/LO): 270/170 mA
  • RF power HI: 1 W
  • RF power LO: 0,2 W
  • Impedance: 50-75 ohm
  • Frequency range: 87,5-108 MHz
  • Modulation type: wide-band FM
  • Modulation inputs: line, mic, RDS/MPX
  • PCB dimensions: 11,3 x 8,8 cm

Please don't forget to report back if you choose to build this circuit.

Alternate References:
mrflash says: (January 6 2008, 12:04am)

Has any body built this transmitter? I'm going to buy the parts and make it... but could anyone give me tips for boosting the output power to maybe 5 watts? A different output transistor or another amp stage?

deki21 says: (January 20 2008, 9:50pm)

Can you give me some manual instruction because i see some switch in RF part 1 between R2 an R3 and on PLL digital Tuning TI31 for what is that switch and on RF part 1 i see RDS/MPX input an some usual input from aduio and power suply please its help me if i have some manual help and can i make some amplifier for the same transmiter about 15WATT thanks

ElectroKits says: (January 20 2008, 10:11pm)


From what I can tell... the switch between R2 and R3 controls the RF output power of the transmitter. It controls the current through T3, which is turn controls the base signal applied to the main RF output transistor T4.

TI31 is a switch related to programming the PIC16F84-04 (IC32). Perhaps someone more familiar with PIC programming can help with the specifics?!

For a 15 Watt RF amplifier - that's definitely possible, but there aren't any amps on here yet. I'll take that suggestion and add some FM RF Amplifiers. Keep an eye open over the coming week or so.

deki21 says: (January 22 2008, 11:11pm)

Ok Thanks when i,m finish everything and when comes programming if i need some help i will ask you thanks again

issa says: (February 27 2008, 10:26am)

thank you verry much fot transmiter circuit i call from iran

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