% Author: Dr. Matthias Jung, DL9MJ
% Year: 2022
\begin{tikzpicture}
    \pgfplotsset{samples=200}
    \begin{axis}[
        height=3cm,
        scale only axis,
        width=\linewidth*\getDarcImageFactor,
        axis lines=none,
        ticks=none,
        xmin =  0,
        ymin = -2.2,
        xmax =  8.8,
        ymax =  2.2,
        domain = 0:8.8,
        thick,
        no markers]
        \addplot+[name path=A,ultra thick, black] { 0.5*sign(sin(deg(x*3.25)))+1.4};
        \addplot+[name path=B,ultra thick, black] {-0.5*sign(sin(deg(x*3.25)))-1.4};
        \addplot[gray, opacity=0.5] fill between[of=A and B];
    \end{axis}
\end{tikzpicture}