I love building crystal radios, especially FM crystal radios. However, you can only receive decent signal for testing FM crystal radio if you are within 10KM of the transmission station. So, many times, I have to travel with my FM crystal radio to somewhere close enough to test it.
How about building this low power FM Transmitter, solely for the educational purpose to test your FM crystal radios at home?
Warning! Using or Owning a radio transmitter without license is illegal in some countries. Please check and decide whether to use one at your own risk.
Follow this video for the demonstration
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Step 1: Components 元件表
5pf x 2
3V CR2032 and socket
0.8mm wire 铜线
1M Telescopic antenna 拉杆天线
4mm Screw - 4mm 缧钉
Build the kit using perf boardsConnect headphone output of phone to the input of the transmitter.
Turn volume to 70% of Max.
Place your FM crystal radio next to the transmitter.
Tune to the frequency of the transmitter.
Move your FM crystal radio further away to test the range. Do not let it transmit outside your room to avoid disrupting your neighbours.
Install the perf board into this tiny plastic box for ease of use.
Adjust the length of the Antenna to resonant with the transmitter frequency.
Power consumption 3mA