By the mid 1960's movable dishes had become as large as engineering and materials would allow Huge dishes the size of a football fields had been contructed in Greenbank, West Virgina and at Jordell Bank, England. The largest dish in the world was formed by carpeting a natural crater in Puerto Rico with metal mesh. The spherical dish used a movable hyperbolic secondard suspended on cables from three towers. A computer controlled controlling the length of the supporting cables steered the antenna's beam.