Description

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).

Circuit diagram

Parts:

Notes:

    Email Rae XL Tkacik with questions, comments, etc.
    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.
    Q1 and Q5 should be cooled with a heat sink. The case-pin of Q4 should be grounded.
    C24 is for the frequency adjustment. The other trimmers must be adjusted to maximum output power with minimum SWR and input current.
    Local laws in some states, provinces or countries may prohibit the operation of this transmitter. Check with the local authorities.

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