</p>

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<table class="bordered">
<tr><td>
<img src="pix/jacobi.png" alt="page from Jacobi's works">
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<tr>
<td class="bluishb">
C G J Jacobi, Gesammelte Werke, VI 101
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</td></tr></table>

<img src="pix/bessel.png" alt="bessel functions">

<p>
As the index sweeps 
upward, energy is swept gradually outward into higher order side bands; this is the originally 
exciting, now extremely annoying "FM sweep".
The important thing to get from these Bessel functions is that the highe