Your faithful editor tried several times back in the early nineties. First effort was building an AM unit from this schematic and it sort of worked - using a 1.0 MHz XTAL it managed to get a block down the road at 790 KHz. It was a weak effort but it got me hooked.
After several spectacular failures, the next successful effort was a small FM kit from the quixotic Free Radio Berkeley. That worked a little too well and earned a NOUO - oops!
Whether it's for serious consideration or simple study, there are vast sources of FM transmitter circuits available on line, here are a few for your consideration
- From Educypedia, the educational encyclopedia, the a massive electronic project library offers a recent curated agglomeration page for FM transmitters
- The former Wonderful World of Electronics, now living on the Internet Archive, offers this low parts count FM transmitter, complete with foil patterns to make your own PCB
- Another project that has moved to the Internet Archive is the fascinating Stable Radio Microphone With Loop Antenna, which also features a YouTube video titled Stable FM Loop Antenna Transmitter
- Looking for a little more range for your low power FM transmitter? Another project that is now on the Internet Archive is the One Watt Class-C Amplifier schematic and 1W FM Amplifier Circuit (Boost Low Power Transmitters) YouTube video - uh, be careful with that one :-)
- Dave Johnson's informative DiscoverCircuits.com "has 30,000+ electronic circuits, cross-referenced into 500+ categories," amongst their circuitry are such diverse elements as a well curated and nicely annotated collection of FM (Frequency Modulation) Transmitter Circuits
- Aaron Cake's long lived site offers a complete set of plans for his low powered FM transmitter and 3 Watt FM Transmitter
- The wide ranging electroschematics.com offers 29 FM Transmitters Circuits and Projects
- Circuitdiagram.org provides a list of free electronic circuit schematics including FM Transmitter Circuits
- Circuit-Zone.com electronic projects offers a page of FM Transmitters
Or, if you prefer to try a Part 15 compliant kit, there are some fun finds on Amazon - FM Transmitter Kits complete with components and PC board - possibly hackable...
You can also try FM transmitter kits from around the world from ebay, some not Part 15 relevant - you have been warned...
Use circuits published by authors who have identified themselves, who have built the project, who are available for questions and who can refer you to others who have had success with the circuit in question.
Because this is the internet, anyone from a well-intended screw-up to a hateful prankster can put an FM schematic online. Your project won't be very satisfying if it's based on a flawed design.