TABLE OF CONTENTS This chapter provides a summary of loss and efficiency-related performance of transmission line transformers, collecting, presenting and discussing data that appeared in various places within earlier editions of this book.
Chapter 1 stated that Guanella conceived the idea of coiling a transmission line in such a manner that only transmission line currents were permitted to flow. The common mode and shorting currents were suppressed. Guanella did not have the great host of ferrites and powdered irons that are available today. In fact, ferrites were first mentioned in the literature in 1944, the year of his classic paper (Ref 1) [1]. Therefore Guanella's 16:1 balun must have been air-wound and of limited use, since it was never mentioned in the literature after his paper was published.
The earliest experiment on the efficiency of transmission line transformers, included in earlier editions of this book, compares 4:1 ununs with and without cores to a 4:1 autotransformer with the same number of turns. The results are shown in Fig 16-1 (which is the same as Fig 3-12). As can be seen in the figure, the 4:1 transmission line transformer with a core had a much higher efficiency and wider bandwidth than the other two. It also shows that the core plays an important role over practically all of the passband. It should also be mentioned that the transmission line transformers did not have transmission lines with optimized characteristic impedances; otherwise, the differences between the auto-transformer and a transmission line transformer...
