\begin{tikzpicture}
	\foreach \a in {1,2,...,18}{
			\draw (\a*360/18: 1cm) node{\color{blue}{$+$}};
		}
	\foreach \a in {1,2,...,36}{
			\draw (\a*360/36: 1.5cm) node{\color{red}{$o$}};
		}

	\draw[thick,->] (-1.6,-1.6) -- (2.5,-1.6);
	\draw[thick,->] (-1.6,-1.6) -- (-1.6,2.5);

\end{tikzpicture}