https://www.ellipticcurve.info/Crystal_radio/history?feed=atom 2026-04-28T17:51:32Z Revision history for this page on the wiki MediaWiki 1.42.3 https://www.ellipticcurve.info/index.php?title=Crystal_radio&diff=551&oldid=prev 2026-04-19T17:56:42Z

<p>minor edits</p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 17:56, 19 April 2026</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1">Line 1:</td> <td colspan="2" class="diff-lineno">Line 1:</td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Building a simple crystal radio is, or ought to be, a basic survival skill.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Building a simple <ins style="font-weight: bold; text-decoration: none;">AM </ins>crystal radio is, or ought to be, a basic survival skill.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This circuit &lt;ref&gt;All About Circuits. &#039;&#039;Textbook // Semiconductors // Practical Analog Semiconductor Circuits // Radio Circuits.&#039;&#039; https://www.allaboutcircuits.com/textbook/semiconductors/chpt-9/radio-circuits/&lt;/ref&gt;</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This circuit &lt;ref&gt;All About Circuits. &#039;&#039;Textbook // Semiconductors // Practical Analog Semiconductor Circuits // Radio Circuits.&#039;&#039; https://www.allaboutcircuits.com/textbook/semiconductors/chpt-9/radio-circuits/&lt;/ref&gt;</div></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>shows an antenna tuned with an inductor of 240μH and a variable capacitor of <del style="font-weight: bold; text-decoration: none;">365pF</del>.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>shows an antenna tuned with an inductor of 240μH and a variable capacitor of <ins style="font-weight: bold; text-decoration: none;">365&amp;nbsp;pF</ins>.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Crystal-radio.png|frame|center|Simple crystal radio circuit]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Crystal-radio.png|frame|center|Simple crystal radio circuit]]</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The resonant frequency for this tuning <del style="font-weight: bold; text-decoration: none;">will be </del>about</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The resonant frequency for this tuning <ins style="font-weight: bold; text-decoration: none;">with the variable capacitor set at 365&amp;nbsp;pF starts at </ins>about</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:&#039;&#039;f&#039;&#039; = 1 / 2π√(LC) =~ 537.73472 kilohertz</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:&#039;&#039;f&#039;&#039; = 1 / 2π√(LC) =~ 537.73472 kilohertz</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>If the variable capacitance is reduced to 36.<del style="font-weight: bold; text-decoration: none;">5pF</del>, 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.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>If the variable capacitance is <ins style="font-weight: bold; text-decoration: none;">''</ins>reduced<ins style="font-weight: bold; text-decoration: none;">'' </ins>to 36.<ins style="font-weight: bold; text-decoration: none;">5&amp;nbsp;pF</ins>, 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.</div></td></tr> </table>

Rational Point https://www.ellipticcurve.info/index.php?title=Crystal_radio&diff=550&oldid=prev 2026-04-19T17:53:12Z

<p>Simple crystal radio circuit</p> <p><b>New page</b></p><div>Building a simple crystal radio is, or ought to be, a basic survival skill.<br /> <br /> This circuit &lt;ref&gt;All About Circuits. &#039;&#039;Textbook // Semiconductors // Practical Analog Semiconductor Circuits // Radio Circuits.&#039;&#039; https://www.allaboutcircuits.com/textbook/semiconductors/chpt-9/radio-circuits/&lt;/ref&gt;<br /> shows an antenna tuned with an inductor of 240μH and a variable capacitor of 365pF.<br /> <br /> [[File:Crystal-radio.png|frame|center|Simple crystal radio circuit]]<br /> <br /> The resonant frequency for this tuning will be about<br /> <br /> :&#039;&#039;f&#039;&#039; = 1 / 2π√(LC) =~ 537.73472 kilohertz<br /> <br /> If the variable capacitance is reduced to 36.5pF, 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.</div>

Rational Point