DIY Variable Capacitor for Homemade AM Radio Receiver

  • Context: High School 
  • Thread starter Thread starter DawsonH
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Discussion Overview

The discussion revolves around constructing a homemade variable capacitor for an AM radio receiver project in a physics course. Participants share suggestions and ideas for achieving the necessary capacitance values to receive two AM radio stations.

Discussion Character

  • Exploratory, Technical explanation, Homework-related

Main Points Raised

  • One participant seeks suggestions for building a variable capacitor without expecting others to do the work for them.
  • Another participant inquires about the required capacitance values for the project.
  • A participant mentions needing to receive two AM radio stations and suggests a capacitance value around 100 pF.
  • One suggestion involves constructing a parallel plate capacitor with an adjustable plate moved by a screw, noting challenges in achieving higher capacitance values.
  • Another participant proposes a coaxial capacitor design, where a rod inside a tube can be adjusted to change capacitance, suggesting it may be easier to construct.
  • A participant shares a resource article on building air variable capacitors.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method for constructing the variable capacitor, and multiple approaches are discussed without resolution.

Contextual Notes

The discussion lacks specific details on the required capacitance values and the assumptions regarding the design constraints for the variable capacitor.

Who May Find This Useful

Individuals interested in DIY electronics, particularly those working on radio receiver projects or studying variable capacitors in a practical context.

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.
 
Last edited:
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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