Crystal radio: Difference between revisions
From Elliptic Curve Crypto
Simple crystal radio circuit |
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Building a simple crystal radio is, or ought to be, a basic survival skill. | Building a simple AM crystal radio is, or ought to be, a basic survival skill. | ||
This circuit <ref>All About Circuits. ''Textbook // Semiconductors // Practical Analog Semiconductor Circuits // Radio Circuits.'' https://www.allaboutcircuits.com/textbook/semiconductors/chpt-9/radio-circuits/</ref> | This circuit <ref>All About Circuits. ''Textbook // Semiconductors // Practical Analog Semiconductor Circuits // Radio Circuits.'' https://www.allaboutcircuits.com/textbook/semiconductors/chpt-9/radio-circuits/</ref> | ||
shows an antenna tuned with an inductor of 240μH and a variable capacitor of | shows an antenna tuned with an inductor of 240μH and a variable capacitor of 365 pF. | ||
[[File:Crystal-radio.png|frame|center|Simple crystal radio circuit]] | [[File:Crystal-radio.png|frame|center|Simple crystal radio circuit]] | ||
The resonant frequency for this tuning | The resonant frequency for this tuning with the variable capacitor set at 365 pF starts at about | ||
:''f'' = 1 / 2π√(LC) =~ 537.73472 kilohertz | :''f'' = 1 / 2π√(LC) =~ 537.73472 kilohertz | ||
If the variable capacitance is reduced to 36. | If the variable capacitance is ''reduced'' to 36.5 pF, then the resonant frequency will be increased to 1700.46649 kilohertz, the other end of the popular AM broadcast radio band, which is about exactly half a decade wide, spanning a ratio of √10 on the radio spectrum. | ||
Latest revision as of 17:56, 19 April 2026
Building a simple AM crystal radio is, or ought to be, a basic survival skill.
This circuit [1] shows an antenna tuned with an inductor of 240μH and a variable capacitor of 365 pF.
The resonant frequency for this tuning with the variable capacitor set at 365 pF starts at about
- f = 1 / 2π√(LC) =~ 537.73472 kilohertz
If the variable capacitance is reduced to 36.5 pF, then the resonant frequency will be increased to 1700.46649 kilohertz, the other end of the popular AM broadcast radio band, which is about exactly half a decade wide, spanning a ratio of √10 on the radio spectrum.
- ↑ All About Circuits. Textbook // Semiconductors // Practical Analog Semiconductor Circuits // Radio Circuits. https://www.allaboutcircuits.com/textbook/semiconductors/chpt-9/radio-circuits/
