% Author: Dr. Matthias Jung, DL9MJ
% Year: 2022
\begin{tikzpicture}
    \pgfplotsset{samples=200}
    \begin{axis}[
        ticks=none,
        xmin =  0,
        ymin = -3,
        xmax =  7,
        ymax =  3,
        domain = 0:7,
        grid=both,
        grid style={line width=.1pt, draw=black},
        major grid style={line width=.2pt,draw=black},
        xtick = {0,1,2,3,4,5,6,7},
        ytick = {-3,-2,-1,0,1,2,3},
        thick,
        smooth,
        no markers]
    \def\foo{1.345}
    \addplot+[name path=A,ultra thick, black] { 
        2.7*(sin(deg(x*\foo))+1/3*sin(deg(3*x*\foo))+0.2*sin(deg(5*x*\foo))+1/7*sin(deg(7*x*\foo)))
    };
    \end{axis}
\end{tikzpicture}