1 INTRODUCTION

　　Transmission line power transformers can be used to perform a variety of functions， among which are phase reversal，

　　balanced to unbalanced coupling， impedance transformation and hybrid functions. Such transformers find many

　　applications in wide-band power amplifiers for both s.s.b. transmitters in the h.f. region and f.m. transmitters in the lower

　　v.h.f. region.

　　The properties of a practical h.f. power transformer are discussed here and their effect on transformer performance is

　　analysed. Since losses must be kept low， in practice the transformer will use a ferrite core. Further， we have limited the

　　discussion to cores without an air-gap since these have a low stray magnetic field， a high permeability， and can cover

　　the power range （up to 80 W） dealt with here. Data （dimensions， permeability values etc.） on all core types can be found

　　in our Data Handbook “Soft Ferrites”， MA01. A glance through the Handbook will show the wide range of materials，

　　dimensions and types from which the designer may choose. It must be remembered， of course， that when cores

　　constructed in two parts （pot-cores and cross-cores， for example） are used， the type without an air-gap must be selected.

　　Throughout we have aimed at giving practical solutions to the problems posed by material and design limitations. In

　　particular， compensating techniques for extending the frequency range of a number of transformer configurations are

　　discussed. To give an idea of some application possibilities， practical examples in several transformer configurations

　　have been worked， using transformer cores from our range of ferrites.