my %packet_fields = (
   $Idents{ Format_7 }	=> qw(	ident
			flags
			x
			y
			mode3
			callsign
			route
			spare1
			spare2
			flight_level
			terminator
			chksum
			),
   $Idents{ Format_7 } => qw(ident
				RDP_Ident
				Radar_Site_Ident
				site_x
				site_y
				Useful_Vol_Upper
				Useful_Vol_Lower
				Useful_Vol_North
				Useful_Vol_South
				Useful_Vol_East
				Useful_Vol_West
				Rotation
				Rotation_x
				Rotation_y
				Reserved
				QNH_Datum
				terminator
				chksum
				),
);