\begin{table}%t2
\caption{Characteristics and performances of the receivers of the 100-m Effelsberg telescope.}\label{tab2}
%\centering
\small
\begin{tabular}{ l l l } 
\hline \hline
$\lambda$ (cm)& 3.6& 6.2  \\
\hline 
Center frequency (GHz)   & 8.350 & 4.850 \\
Band width (MHz)    & 1100  & 500 \\
{\it HPBW} ($\arcsec$)   & 83.6 & 146\\
$T_{\rm sys}$ (K)    & 23--25 & 25--28 \\
$T_{\rm b}/S_{\nu}$ (K/Jy)  & 2.62 & 2.4 \\
\hline
\end{tabular}
\end{table}