Hello home builders, this is the FCC part 15 version of the Altoids Tin FM Transmitter. A fixed antenna of 36 inches of 18awg wire and a lower operating voltage of 9 volts, keeps this unit's emissions below the FCC maximum allowable for part 15.

Circuit Description: The transmitter uses 2 MPSH10 (equiv BF494 or NTE229) transistors in a double-ended free-running voltage controlled oscillator (VCO) operating at half the output frequency on each side and combined at L2, which is tuned to the 2nd harmonic of the VCO and covers the 88-108 MHz range. A standard 9 volt battery is used for power and fits inside the tin. The mono audio input circuit is totally passive with 70us pre-emphasis provided and the audio quality is great.

The unit is constructed with copper clad board, a large piece is used as the construction surface and is soldered into the tin. Three small boards are made using scissors and a dremel tool or file (see the pcb diagrams). On them, the largest is for the L1 coil assembly, another for the oscillator transistors and the smallest is for the varicap diodes and trim capacitor. Other board material is cut into small pads, then glued to the construction surface for the remaining part connections.

- DJ Pirate Joe