Here are some quick notes about the parabolic type dish antennas you might find.  The actual antenna is a normal half wave dipole with an integrated balun and is located inside the sealed plastic cover.  The mesh screen is the reflector which concentrates the RF energy onto the antenna.  That is how dish antennas increase the received or transmitted power level.  Also, wireless cable service providers frown upon giving away their used dishes as they think you're going to steal cable service.