DIY Variable Capacitor for Homemade AM Radio Receiver

AI Thread Summary
For constructing a homemade AM radio receiver, a variable capacitor around 100 picofarads (pF) is recommended to effectively receive two AM stations. Suggestions include creating a parallel plate capacitor with an adjustable plate moved by a screw, although achieving higher capacitance may be challenging. An alternative design is a coaxial capacitor, featuring a rod inside a tube, which allows for easy adjustment of the inner rod's position via a screw mechanism. Resources, such as articles on building air variable capacitors, can provide additional guidance for the construction process.
DawsonH
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I have to make a homemade AM radio receiver for a physics course I'm doing, and I'm looking for any suggestions on the best way to make a homemade variable capacitor. I'm not expecting anyone to do my work for me of course, but any suggestions that anyone could offer would be appreciated.
 
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Do you know values required?
 
I need to be able to receive two AM radio stations. I haven't figured out what values I need yet. I'm just looking for different suggestions about how to construct one.

Edit: Maybe something around the 100 pf range.
 
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You can make a reasonable parallel plate cap with one adjustable plate that is moved by a screw. But to get more than a couple of tens of pFs, may be tricky (unless you just make a big box).

Easier still may be a (cylindrical or) coaxial cap (a rod inside a tube), with the position of the inside rod adjusted by means of a simple screw.
 
Here is an article on building air variable capacitors.

Mark
 

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