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Unsourced material may be challenged and <a href="/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22Superheterodyne+transmitter%22">"Superheterodyne transmitter"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Superheterodyne+transmitter%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Superheterodyne+transmitter%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22Superheterodyne+transmitter%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Superheterodyne+transmitter%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Superheterodyne+transmitter%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">March 2010</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Transmitters using intermediate frequency</div> <p><b>Superheterodyne transmitter</b> is a <a href="/wiki/Radio" title="Radio">radio</a> or <a href="/wiki/TV" class="mw-redirect" title="TV">TV</a> transmitter which uses an intermediate frequency signal in addition to radio frequency signal. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Types_of_transmitters">Types of transmitters</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Superheterodyne_transmitter&action=edit&section=1" title="Edit section: Types of transmitters"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Superheterodyne_transmitter.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Superheterodyne_transmitter.jpg/550px-Superheterodyne_transmitter.jpg" decoding="async" width="550" height="281" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/0/0a/Superheterodyne_transmitter.jpg 1.5x" data-file-width="567" data-file-height="290" /></a><figcaption>Above: Direct modulation, below superheterodyne transmitter</figcaption></figure> <p>There are two types of transmitters. In some transmitters, the information signal (<a href="/wiki/Audio_signal" title="Audio signal">audio (AF)</a>, <a href="/wiki/Video_signal" class="mw-redirect" title="Video signal">video (VF)</a> etc.) modulates the <a href="/wiki/Radio_frequency" title="Radio frequency">radio frequency (RF)</a> signal. These direct modulation transmitters are relatively simple transmitters. </p><p>In more complicated transmitters which are called superheterodyne, the information signal modulates an <a href="/wiki/Intermediate_frequency" title="Intermediate frequency">intermediate frequency (IF)</a> signal. After stages for correction, equalization and sometimes amplification, the IF signal is converted to an RF signal by a stage named <a href="/wiki/Frequency_mixer" title="Frequency mixer">frequency mixer</a> or frequency converter. Superheterodyne transmitters are more complex than direct modulation transmitters.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (October 2011)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading2"><h2 id="Mathematical_approach">Mathematical approach</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Superheterodyne_transmitter&action=edit&section=2" title="Edit section: Mathematical approach"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Let </p> <dl><dd><b><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle f(t)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f(t)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5bf044fe2fbfc4bd8d6d7230f4108430263f9fd6" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:3.927ex; height:2.843ex;" alt="{\displaystyle f(t)}"></span></b> be the information signal</dd> <dd><b><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \omega _{R}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \omega _{R}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5118d7819b13e2e0d69ac00942dfb1836ec70886" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.925ex; height:2.009ex;" alt="{\displaystyle \omega _{R}}"></span> </b>be the angular RF,</dd> <dd><b><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \omega _{I}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>I</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \omega _{I}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/155591cc9682c1b01887df43391234ce7ae03d12" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.507ex; height:2.009ex;" alt="{\displaystyle \omega _{I}}"></span></b> be the angular IF and</dd> <dd><b><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \omega _{s}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \omega _{s}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f9458d02624326fd1e59de34085a48f2167481b9" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.449ex; height:2.009ex;" alt="{\displaystyle \omega _{s}}"></span></b> be the angular subcarrier frequency.</dd></dl> <p>In direct modulation transmitter the information signal modulates the RF carrier. If the type of modulation is conventional <a href="/wiki/Amplitude_modulation" title="Amplitude modulation">amplitude modulation</a> the RF output is, </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{RF}}=(1+f(t))\cdot \sin(\omega _{R}t)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>RF</mtext> </mstyle> </mrow> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>f</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> <mo>⋅</mo> <mi>sin</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{RF}}=(1+f(t))\cdot \sin(\omega _{R}t)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ee456ded98d18d2cd221a40542b2735fb2925e07" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:26.176ex; height:2.843ex;" alt="{\displaystyle {\mbox{RF}}=(1+f(t))\cdot \sin(\omega _{R}t)}"></span></dd></dl> <p>Likewise in superheterodyne transmitter the modulated IF is; </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{IF}}=(1+f(t))\cdot \sin(\omega _{I}t)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>IF</mtext> </mstyle> </mrow> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>f</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> <mo>⋅</mo> <mi>sin</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>I</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{IF}}=(1+f(t))\cdot \sin(\omega _{I}t)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6b677f85fee867c8f1fed6b111323bce1ee40951" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:24.886ex; height:2.843ex;" alt="{\displaystyle {\mbox{IF}}=(1+f(t))\cdot \sin(\omega _{I}t)}"></span></dd></dl> <p>This signal is applied to a frequency mixer. The other input to the mixer is a high frequency subcarrier signal. </p> <dl><dd><b><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{SC}}=\sin(\omega _{s}t)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>SC</mtext> </mstyle> </mrow> <mo>=</mo> <mi>sin</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{SC}}=\sin(\omega _{s}t)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/31c6cb191739c2842ef9bce40b62cfd736d315b2" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:14.023ex; height:2.843ex;" alt="{\displaystyle {\mbox{SC}}=\sin(\omega _{s}t)}"></span></b></dd></dl> <p>The two signals are multiplied to give; </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{IF}}\cdot {\mbox{SC}}=(1+f(t))\cdot \sin(\omega _{I}t)\cdot \sin(\omega _{s}t)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>IF</mtext> </mstyle> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>SC</mtext> </mstyle> </mrow> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>f</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> <mo>⋅</mo> <mi>sin</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>I</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> <mo>⋅</mo> <mi>sin</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{IF}}\cdot {\mbox{SC}}=(1+f(t))\cdot \sin(\omega _{I}t)\cdot \sin(\omega _{s}t)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/22d28b94cc8f04e766b211eedbbeabfcf165ed41" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:39.168ex; height:2.843ex;" alt="{\displaystyle {\mbox{IF}}\cdot {\mbox{SC}}=(1+f(t))\cdot \sin(\omega _{I}t)\cdot \sin(\omega _{s}t)}"></span></dd></dl> <p>Applying well known rules of <a href="/wiki/Trigonometry" title="Trigonometry">trigonometry</a>; </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{IF}}\cdot {\mbox{SC}}={\frac {1}{2}}(1+f(t))\cdot (\cos(\omega _{s}t-\omega _{I}t)-\cos(\omega _{s}t+\omega _{I}t))}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>IF</mtext> </mstyle> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>SC</mtext> </mstyle> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>f</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> <mo>⋅</mo> <mo stretchy="false">(</mo> <mi>cos</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> <mi>t</mi> <mo>−</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>I</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> <mo>−</mo> <mi>cos</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> <mi>t</mi> <mo>+</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>I</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{IF}}\cdot {\mbox{SC}}={\frac {1}{2}}(1+f(t))\cdot (\cos(\omega _{s}t-\omega _{I}t)-\cos(\omega _{s}t+\omega _{I}t))}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/af31468f80aecee9e3eede15f36ae83c657fb807" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:56.964ex; height:5.176ex;" alt="{\displaystyle {\mbox{IF}}\cdot {\mbox{SC}}={\frac {1}{2}}(1+f(t))\cdot (\cos(\omega _{s}t-\omega _{I}t)-\cos(\omega _{s}t+\omega _{I}t))}"></span></dd></dl> <p>A filter at the output of the mixer filters out one of the terms at the right (usually the summation) leaving RF </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{RF}}={\frac {1}{2}}(1+f(t))\cdot \cos(\omega _{s}t-\omega _{I}t)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>RF</mtext> </mstyle> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>f</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> <mo>⋅</mo> <mi>cos</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> <mi>t</mi> <mo>−</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>I</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{RF}}={\frac {1}{2}}(1+f(t))\cdot \cos(\omega _{s}t-\omega _{I}t)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d38cebcc9822636081549115c0f27d7cb3f2800e" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:34.14ex; height:5.176ex;" alt="{\displaystyle {\mbox{RF}}={\frac {1}{2}}(1+f(t))\cdot \cos(\omega _{s}t-\omega _{I}t)}"></span></dd></dl> <p>Here <b><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \omega _{s}-\omega _{I}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> <mo>−</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>I</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \omega _{s}-\omega _{I}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/34d762206039a3d035422ac90ab7f21c50f65a3c" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:7.796ex; height:2.343ex;" alt="{\displaystyle \omega _{s}-\omega _{I}}"></span></b> is the required angular RF; i.e.,<b> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \omega _{R}=\omega _{s}-\omega _{I}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>s</mi> </mrow> </msub> <mo>−</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>I</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \omega _{R}=\omega _{s}-\omega _{I}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/15f4846ccb5d20cc31d861e34369c80ad5d270e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:13.82ex; height:2.343ex;" alt="{\displaystyle \omega _{R}=\omega _{s}-\omega _{I}}"></span></b> </p><p>After phase and amplitude equalization, </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{RF}}=(1+f(t))\cdot \sin(\omega _{R}t)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>RF</mtext> </mstyle> </mrow> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>f</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> <mo>⋅</mo> <mi>sin</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <msub> <mi>ω</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{RF}}=(1+f(t))\cdot \sin(\omega _{R}t)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ee456ded98d18d2cd221a40542b2735fb2925e07" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:26.176ex; height:2.843ex;" alt="{\displaystyle {\mbox{RF}}=(1+f(t))\cdot \sin(\omega _{R}t)}"></span></dd></dl> <div class="mw-heading mw-heading2"><h2 id="Advantages_of_superheterodyne">Advantages of superheterodyne</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Superheterodyne_transmitter&action=edit&section=3" title="Edit section: Advantages of superheterodyne"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>In transmitters several correction and equalization stages are used after modulation. In direct modulation these stages must be developed separately for each output RF (so called channel). On the other hand, in superheterodyne transmitters since a single intermediate frequency signal is used, only one type of stage for IF is developed. Thus the said stages are more reliable in superheterodyne. Also <a href="/wiki/R%26D" class="mw-redirect" title="R&D">R&D</a> is much easier for the designer.</li> <li>Operators may change the RF output of the transmitter. In direct modulation, it is very difficult to change the RF output. Because in this case, practically all stages need to be retuned for the new RF. On the other hand, in superheterodyne only the output stages need to be retuned.</li> <li>With a fast enough <a href="/wiki/Digital-to-analog_converter" title="Digital-to-analog converter">DAC</a>, the modulated IF signal can be generated directly, digitally from a <a href="/wiki/Microprocessor" title="Microprocessor">microprocessor</a> or a <a href="/wiki/Digital_signal_processor" title="Digital signal processor">digital signal processor</a>. This will permit usage of more advanced methods of modulation without the use of complicated modulator hardware, and make <a href="/wiki/Software-defined_radio" title="Software-defined radio">software-defined radio</a> possible.</li></ul> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Superheterodyne_transmitter&action=edit&section=4" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Superheterodyne_receiver" title="Superheterodyne receiver">Superheterodyne receiver</a></li> <li><a href="/wiki/TV_transmitter_topics" class="mw-redirect" title="TV transmitter topics">TV transmitter topics</a></li> <li><a href="/wiki/TV_transmitters" class="mw-redirect" title="TV transmitters">TV transmitters</a></li></ul> <p><br /> </p> <div class="navbox-styles"><style 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title="Analog television">Analog television</a> <a href="/wiki/Outline_of_television_broadcasting" title="Outline of television broadcasting">broadcasting topics</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Broadcast_television_systems" title="Broadcast television systems">Systems</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/180-line_television_system" title="180-line television system">180-line</a></li> <li><a href="/wiki/343-line_television_system" title="343-line television system">343-line</a></li> <li><a href="/wiki/375-line_television_system" title="375-line television system">375-line</a></li> <li><a href="/wiki/405-line_television_system" title="405-line television system">405-line</a> (<a href="/wiki/CCIR_System_A" title="CCIR System A">System A</a>)</li> <li><a href="/wiki/441-line_television_system" title="441-line television system">441-line</a></li> <li><a href="/wiki/455-line_television_system" title="455-line television system">455-line</a></li> <li><a href="/wiki/525-line_television_system" class="mw-redirect" title="525-line television system">525-line</a> (<a href="/wiki/CCIR_System_M" title="CCIR System M">System M</a>)</li> <li><a href="/wiki/625-line_television_system" class="mw-redirect" title="625-line television system">625-line</a> (<a href="/wiki/CCIR_System_B" title="CCIR System B">System B</a>, <a href="/wiki/CCIR_System_C" title="CCIR System C">System C</a>, <a href="/wiki/CCIR_System_D" title="CCIR System D">System D</a>, <a href="/wiki/CCIR_System_G" title="CCIR System G">System G</a>, <a href="/wiki/CCIR_System_H" title="CCIR System H">System H</a>, <a href="/wiki/CCIR_System_I" title="CCIR System I">System I</a>, <a href="/wiki/CCIR_System_K" title="CCIR System K">System K</a>, <a href="/wiki/CCIR_System_L" title="CCIR System L">System L</a>, <a href="/wiki/CCIR_System_N" title="CCIR System N">System N</a>)</li> <li><a href="/wiki/819_line" title="819 line">819-line</a> (<a href="/wiki/CCIR_System_E" title="CCIR System E">System E</a>, <a href="/wiki/CCIR_System_E#System_F" title="CCIR System E">System F</a>)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Color systems</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/NTSC" title="NTSC">NTSC</a></li> <li><a href="/wiki/NTSC-J" title="NTSC-J">NTSC-J</a></li> <li><a href="/wiki/Clear-Vision" title="Clear-Vision">Clear-Vision</a></li> <li><a href="/wiki/PAL" title="PAL">PAL</a></li> <li><a href="/wiki/PAL-M" title="PAL-M">PAL-M</a></li> <li><a href="/wiki/PAL-S" title="PAL-S">PAL-S</a></li> <li><a href="/wiki/PALplus" title="PALplus">PALplus</a></li> <li><a href="/wiki/SECAM" title="SECAM">SECAM</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Video</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Analog_television#Structure_of_a_video_signal" title="Analog television">Back porch</a> and <a href="/wiki/Analog_television#Structure_of_a_video_signal" title="Analog television">front porch</a></li> <li><a href="/wiki/Black_level" title="Black level">Black level</a></li> <li><a href="/wiki/Blanking_level" title="Blanking level">Blanking level</a></li> <li><a href="/wiki/Chrominance" title="Chrominance">Chrominance</a></li> <li><a href="/wiki/Chrominance_subcarrier" title="Chrominance subcarrier">Chrominance subcarrier</a></li> <li><a href="/wiki/Colorburst" title="Colorburst">Colorburst</a></li> <li><a href="/wiki/Color_killer" title="Color killer">Color killer</a></li> <li><a href="/wiki/Color_television" title="Color television">Color TV</a></li> <li><a href="/wiki/Composite_video" title="Composite video">Composite video</a></li> <li><a href="/wiki/Frame_(video)" class="mw-redirect" title="Frame (video)">Frame (video)</a></li> <li><a href="/wiki/Horizontal_scan_rate" title="Horizontal scan rate">Horizontal scan rate</a></li> <li><a href="/wiki/Horizontal_blanking_interval" title="Horizontal blanking interval">Horizontal blanking interval</a></li> <li><a href="/wiki/Luma_(video)" title="Luma (video)">Luma</a></li> <li><a href="/wiki/Nominal_analogue_blanking" title="Nominal analogue blanking">Nominal analogue blanking</a></li> <li><a href="/wiki/Overscan" title="Overscan">Overscan</a></li> <li><a href="/wiki/Raster_scan" title="Raster scan">Raster scan</a></li> <li><a href="/wiki/Safe_area_(television)" title="Safe area (television)">Safe area</a></li> <li><a href="/wiki/Television_lines" title="Television lines">Television lines</a></li> <li><a href="/wiki/Vertical_blanking_interval" title="Vertical blanking interval">Vertical blanking interval</a></li> <li><a href="/wiki/White_clipper" title="White clipper">White clipper</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Sound</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Multichannel_television_sound" class="mw-redirect" title="Multichannel television sound">Multichannel television sound</a></li> <li><a href="/wiki/NICAM" title="NICAM">NICAM</a></li> <li><a href="/wiki/Sound-in-Syncs" title="Sound-in-Syncs">Sound-in-Syncs</a></li> <li><a href="/wiki/Zweikanalton" title="Zweikanalton">Zweikanalton</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Modulation</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Frequency_modulation" title="Frequency modulation">Frequency modulation</a></li> <li><a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">Quadrature amplitude modulation</a></li> <li><a href="/wiki/Single-sideband_modulation#Vestigial_sideband_(VSB)" title="Single-sideband modulation">Vestigial sideband modulation (VSB)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Transmission</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Amplifier#Electronic_amplifiers" title="Amplifier">Amplifiers</a></li> <li><a href="/wiki/Antenna_(radio)" title="Antenna (radio)">Antenna (radio)</a></li> <li><a href="/wiki/Broadcast_transmitter" title="Broadcast transmitter">Broadcast transmitter</a>/<a href="/wiki/Transmitter_station" title="Transmitter station">Transmitter station</a></li> <li><a href="/wiki/Resonator#Electromagnetic" title="Resonator">Cavity amplifier</a></li> <li><a href="/wiki/Differential_gain" title="Differential gain">Differential gain</a></li> <li><a href="/wiki/Differential_phase" title="Differential phase">Differential phase</a></li> <li><a href="/wiki/Diplexer" title="Diplexer">Diplexer</a></li> <li><a href="/wiki/Dipole_antenna" title="Dipole antenna">Dipole antenna</a></li> <li><a href="/wiki/Dummy_load" title="Dummy load">Dummy load</a></li> <li><a href="/wiki/Frequency_mixer" title="Frequency mixer">Frequency mixer</a></li> <li><a href="/wiki/Intercarrier_method" title="Intercarrier method">Intercarrier method</a></li> <li><a href="/wiki/Intermediate_frequency" title="Intermediate frequency">Intermediate frequency</a></li> <li><a href="/wiki/Output_power_of_an_analog_TV_transmitter" title="Output power of an analog TV transmitter">Output power of an analog TV transmitter</a></li> <li><a href="/wiki/Pre-emphasis" class="mw-redirect" title="Pre-emphasis">Pre-emphasis</a></li> <li><a href="/wiki/Residual_carrier" title="Residual carrier">Residual carrier</a></li> <li><a href="/wiki/Split_sound_system" title="Split sound system">Split sound system</a></li> <li><a class="mw-selflink selflink">Superheterodyne transmitter</a></li> <li><a href="/wiki/Television_receive-only" title="Television receive-only">Television receive-only</a></li> <li><a href="/wiki/Direct-broadcast_satellite_television" class="mw-redirect" title="Direct-broadcast satellite television">Direct-broadcast satellite television</a></li> <li><a href="/wiki/Television_transmitter" title="Television transmitter">Television transmitter</a></li> <li><a href="/wiki/Terrestrial_television" title="Terrestrial television">Terrestrial television</a></li> <li><a href="/wiki/Transposer" title="Transposer">Transposer</a></li> <li><a href="/wiki/Digital_television_transition" title="Digital television transition">Digital television transition</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Radio_frequency" title="Radio frequency">Frequencies</a> & bands</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Frequency_offset" title="Frequency offset">Frequency offset</a></li> <li><a href="/wiki/Microwave_transmission" title="Microwave transmission">Microwave transmission</a></li> <li><a href="/wiki/Television_channel_frequencies" title="Television channel frequencies">Television channel frequencies</a></li> <li><a href="/wiki/Ultra_high_frequency" title="Ultra high frequency">UHF</a></li> <li><a href="/wiki/Very_high_frequency" title="Very high frequency">VHF</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Radio_propagation" title="Radio propagation">Propagation</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Beam_tilt" title="Beam tilt">Beam tilt</a></li> <li><a href="/wiki/Distortion" title="Distortion">Distortion</a></li> <li><a href="/wiki/Earth_bulge" class="mw-redirect" title="Earth bulge">Earth bulge</a></li> <li><a href="/wiki/Field_strength_in_free_space" class="mw-redirect" title="Field strength in free space">Field strength in free space</a></li> <li><a href="/wiki/Noise_(electronics)" title="Noise (electronics)">Noise (electronics)</a></li> <li><a href="/wiki/Null_fill" title="Null fill">Null fill</a></li> <li><a href="/wiki/Path_loss" title="Path loss">Path loss</a></li> <li><a href="/wiki/Radiation_pattern" title="Radiation pattern">Radiation pattern</a></li> <li><a href="/wiki/Skew_(antenna)" title="Skew (antenna)">Skew</a></li> <li><a href="/wiki/Television_interference" title="Television interference">Television interference</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Testing</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Distortionmeter" title="Distortionmeter">Distortionmeter</a></li> <li><a href="/wiki/Field_strength_meter" title="Field strength meter">Field strength meter</a></li> <li><a href="/wiki/Vectorscope" title="Vectorscope">Vectorscope</a></li> <li><a href="/wiki/VIT_signals" title="VIT signals">VIT signals</a></li> <li><a href="/wiki/Zero_reference_pulse" title="Zero reference pulse">Zero reference pulse</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Artifacts</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Dot_crawl" title="Dot crawl">Dot crawl</a></li> <li><a href="/wiki/Ghosting_(television)" title="Ghosting (television)">Ghosting</a></li> <li><a href="/wiki/Hanover_bars" title="Hanover bars">Hanover bars</a></li> <li><a href="/wiki/Sparklies" 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