Build a simple single-stage FK702 FM Transmitter Kit by Future Kit.
I’ve been experimenting with FM, and the hardest thing to get right tends to be the hand-wound coils. So to get a baseline, I picked up a 1-transistor kit during a recent visit to Sim Lim Tower.
The kit is the FK702 by Future Kit. It takes the hastle out of getting the LC circuit right by printing the inductor coil on the PCB (used in conjuction with a trimmer capacitor).
The PCB includes +9V and GND connectors.
Optional Transmit-enable switch
The PCB includes connections for an optional transmit switch (not included). I put a switch in my build.
tl;dr: Not that great!
With the supplied coil antenna, I don’t get much more than a metre range before the signal is lost to noise.
Adding 30cm rabbit ears gives about 5m.
Frequency is quite selective which is good, but stability is a bit all over the place - it will drift and jump over time.
Here’s a trace of the signal and FFT when tuned at 83.25MHz: