How do I connect a variable capacitor to an inductor in a crystal radio circuit?

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Discussion Overview

The discussion revolves around the connection of a variable capacitor to an inductor within a crystal radio circuit. Participants explore the wiring configurations and the relationship between the components, focusing on practical assembly rather than theoretical principles.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant seeks clarification on how to connect a variable capacitor to an inductor, expressing confusion over the wiring process.
  • Another participant suggests that the inductor should be connected across the capacitor, indicating that the connection points are largely a matter of convenience.
  • A different participant questions the validity of various proposed connection methods, seeking a definitive answer on the correct wiring configuration.
  • One participant explains that the capacitor has two sets of plates and clarifies that one end of the inductor can connect to either the movable or stationary plates of the capacitor.
  • Concerns are raised about the safety of a linked website, prompting a request for direct image attachment.
  • Another participant notes the physical construction of the capacitor, indicating how the stationary plates are connected to the feet and the chassis.
  • A participant shares a link that may provide additional guidance on the topic.
  • In a later post, a participant summarizes that any of the feet can serve as a positive terminal while the chassis can act as the negative terminal.

Areas of Agreement / Disagreement

Participants express differing views on the correct method of connecting the inductor to the variable capacitor, with no consensus reached on a single correct approach. Multiple configurations are proposed, and some participants challenge the validity of these suggestions.

Contextual Notes

Participants highlight the importance of understanding the physical connections and the roles of various components, but there is uncertainty regarding the implications of different wiring methods and their effects on circuit functionality.

mearvk
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Typical VC: http://goo.gl/Z4Dbg

I have that guy there or one very similar. My question is how does one hook this up to the inductor? Forget, for now, the rest of the circuit. How do these two piece fit together?

The bottom feet (there are two on each side) I assume take the positive terminal of the inductor and the ground gets soldered to the chassis of the variable capacitor? Then would I connect any power source the same way? Positive to a free foot and negative to the chassis? Or would I hook up the positive to one side of the inductor and negative to the other side? And then to get output from the circuit what would I do?

I've watched a ton of videos and they all neglect how to wire these two guys together.

Thanks.

Crystal radio diagram: http://goo.gl/bZlpM
 
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There are a number of connection points on each side of the capacitor.

To make a parallel tuned circuit, the inductor has to go across the capacitor. The actual point of connection is mostly related to convenience.

You could have one side of the inductor and one side of the capacitor grounded because then the two would be joined together.

You would not normally put a power source directly across a variable capacitor.
 
I'm not sure if this world is intentionally obtuse or what.

Very clearly the inductor goes across the VC. This is clear. What I don't know is how. You say it's a matter of convenience. So I can connect any old way?

I can connect the inductor across the feet, neglecting the VC chassis completely.

I can connect the inductor solely to the chassis of the VC, ignoring the feet connections.

I can connect the inductor from the feet to the chassis.

Now that I've gone out of my way to enumerate the possibilities which is correct? Likely that they're all not correct. And again, once this part is correct what does the output look like? Where is it connected?
 
None of those is correct.

The capacitor has two sets of plates. One set is stationary and the other set is movable,

The movable set is connected to the body of the the capacitor and also to the feet. So, one end of the inductor can connect to any of these.

The other end of the inductor has to connect to the stationary plates of the capacitor which are the top ones in the picture in the first post.
 
Your first link is begin flagged as a known malicious website by my Norton antivirus.
Can you attach the image directly?
 
DQa1C.jpg


The stationary plates appear connected to the feet via soldering. The wood serves to isolate the stationary metal from the chassis which appears to connect to the moving piece via the bronze looking rod. So we're clear.
 
Last edited:
Looks good. So for future reference it looks like any of the feet will do for your positive terminal and the chassis will do as your negative (ground) terminal.
 

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