1:1 ATU Current Balun 1-54 MHz 5kW 1171t

This balun is NOT wound with the normal 50 ohm pair, instead the design criteria is maximizing inter-conductor breakdown voltage.  Consequently, this design is intended primarily for use with multiband wire antennas such as doublets and loops where there will be a wide range of impedance values generated across the different bands and a tuner is required for the final match.  Use with resonant monoband wire antennas is not recommended.

With wire antennas being used primarily on the lower HF bands, choking impedance for this balun has been shifted to provide maximum performance on the 160m through 40m bands. However, this ferrite mix also provides excellent common mode control on the upper HF bands where high choking impedance levels are not as critical. It is best installed outdoors to minimize the chance of RF entering the operating position from the balanced feedline.

Typically this balun is utilized with a tuner that can easily match a wide set of impedance values. 

 Design Criteria

– T match antenna tuners perform quite poorly if the resistive component of load impedance is very low, even worse if there is also a high capacitive reactive component. This is a common load found in shortened dipoles fed with open wire line.

– The traditional approach is to use a 4:1 balun on such antennas, but antenna tuner loss is worse with low resistive loads.

– The need to tolerate high voltages occurs when the balun happens to be located near a differential voltage maximum.

– Generation of high choking impedance for effective reduction of common mode current.

– Balun is intended for use with an antenna tuner which will manage SWR and transformation mismatches.

– Differential insertion loss is not significant in this application, the dissipation in a current balun is primarily from the common mode current which is installation dependent and not easily predicted.

Specifications