\begin{table}%t2
\caption{\label{table:2}Beam efficiencies for the different receivers.}           
%\centering
\par
\begin{tabular}{c c c}
\hline\hline\noalign{\smallskip}          
Receiver & Forward efficiency &Beam efficiency \\  
\hline                        
   APEX-2A 290 GHz & 0.97 & 0.80 \\
   APEX-2A 350 GHz & 0.97 & 0.73 \\
   FLASH 460 GHz   & 0.95 & 0.60 \\
   FLASH 810 GHz   & 0.95 & 0.43 \\
\hline                                   
\end{tabular}
\end{table}