J.L. (BS Physics, University of Houston; MS Engineering, Southern Methodist University) Smith 
Basic NEC with Broadcast Applications [PDF ebook] 

Basic NEC with Broadcast Applications addresses computer modeling of MF directional broadcast antennas and illustrates the assets and liabilities of the Numerical Electromagnetic Code (NEC). The book”s ‘how to’ approach reveals the fundamentals of NEC operation, teaches broadcast applications and shows the reader how to use NEC-2 to: model non-radiating networks, verify calculations, detune unused towers, design top-loaded and skirted antennas, minimize coding by moving and duplicating structures, and much more! Complete with downloadable resources, the book is an invaluable toolkit with software necessary for the design and analysis of broadcast antenna arrays.