I tried to remake some antique crystal radios like pen point pen crystal radio using modern components.
You can fast tune by pulling the ferrite rod stuck to the ink refill inside the pen, or turn it to fine tune through a screw hidden inside the pen.
Here are the high level steps. Refer details to this youtube video.
How to make it: 如何制作：
1. The circuit 建立电路
2. The coil 绕线圈
3. Tuning Rod 调台旋纽杆
4. Earbud/antenna 耳塞/天线插孔
5. Hook up and test 连接并测试
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