A Very-Wide-Band Balun Transformer for VHF and UHF

A transformer is described which may be used as a phase inverter, a differential transformer, or as a balun transformer. Practical models have been built which operate over more than two decades of frequency range with bandwidths approaching 1 kmc. Insertion loss in a typical transformer fluctuates between 1 and 2 db over the range of frequencies from 5 to 1000 mc. For successful operation the transformer depends upon the magnetic properties of a suitable ferrite core material and not upon the usual resonant lines or cavities commonly utilized with such devices [1]-[3]. The ferrites used are not of the low loss, UHF variety but rather are selected on the (approximate) criterion of yielding a high absolute value of permeability over the entire frequency range, and are typically of a class intended for use at much lower frequencies.