# Lesson 16 — EP for Communications

<p class="block-synopsis">The same spread-spectrum instinct that protects a radar protects a data link. We smear a narrowband signal into noise with DSSS and FHSS, quantify the processing gain that lets a link survive a louder jammer, and ride a signal below the noise floor.</p>

<div class="block-toc">
  <a class="bt-card bt-reading" href="L16_EPForCommunications_Reading.html">
    <span class="bt-kind">Reading</span>
    <h4>EP for Communications</h4>
    <p>Why narrowband is easy to jam, DSSS vs FHSS, processing gain $=10\log_{10}N_\text{chips}$, J/S relief, and LPD.</p>
  </a>
  <a class="bt-card bt-flashcards" href="L16_Flashcards.html">
    <span class="bt-kind">Flashcards</span>
    <h4>Review deck</h4>
    <p>Key terms and relations from the lesson, in a self-test deck.</p>
  </a>
  <a class="bt-card bt-demo" href="L16_SpreadSpectrumPlayground_Demo.html">
    <span class="bt-kind">Demo</span>
    <h4>Spread-Spectrum Playground</h4>
    <p>Despread a signal to concentrate it and spread the jammer, and watch the BER collapse as $G_p$ clears the deficit.</p>
  </a>
  <a class="bt-card" href="L16_Preflight.html">
    <span class="bt-kind">Pre-flight</span>
    <h4>Pre-flight quiz</h4>
    <p>Pre-class check, due before the lesson. Counts toward your IP grade.</p>
  </a>
</div>