"End effect", which is inherent with the Yagi, is absent in a quad because its elements have no ends. Moore's design eliminated interference from coronal discharge. Our prayers must have been answered, for gradually as we worked the vision of a quad-shaped antenna gradually grew with the new concept of a loop antenna having no ends to the elements, and combining relatively high transmitting impedance and high gain. There on the floor of our bamboo cottage we spread open all the reference books we had brought with us and worked for hours on basic antenna design.
We took about one hundred pounds of engineering reference books with us on our short vacation to Posoraja, Ecuador during the summer of 1942, determined that with the help of God we could solve our problem. It is a further object of the present invention to provide a loop antenna having an even number of turns of a length of one or more wave lengths around each turn in which substantially no voltage components are present and the only voltage existing is that due to the impedance between the adjacent loops. While the main point of Moore's patent was the two turn single loop design which is not the antenna termed "quad" today, the patent does include a mention and illustration of a two element unidirectional "quad", and describes the time when the full wave loop concept was developed: Moore describes his antenna as "a pulled-open folded dipole". He developed this antenna to resolve issues caused by large coronal discharges while using a beam antenna in the thin air of higher altitudes.
Moore, W9LZX, a Christian Missionary and engineer at HCJB (a shortwave missionary radio station high in the Andean Mountains) developed and patented a two-turn loop antenna that he called a "quad".
patented a loop antenna with rhombic shape and quarterwave sides. In 1924, Moses Jacobson patented a loop antennas with rhombic shape.The quad antenna is a development of several inventions. 3 Disadvantages compared to other antennas.