The Design of Doublet Antenna Systems

An antenna system has been designed for all-wave radio reception at 0.54 to eighteen megacycles with reduction of noise from causes near the receiver. The system includes doublet antenna, transmission line and coupling filters. The fifteen-meter double V doublet is designed on the basis of impedance curves, for satisfactory balanced operation at six to eighteen megacycles. Unbalanced operation is employed at the lower frequencies. Each of the antenna-to-line and line-to-receiver filters includes low band and high band transformers together passing the entire frequency range with little attenuation. The antenna transformers are included in contiguous band filters for switching the antenna between unbalanced and balanced operation. The receiver transformers are included in a continuous band filter. Balanced operation of the line is carefully preserved. The over-all loss is measured with the aid of a special dummy antenna. The over-all loss, minus the line attenuation, is between one and five decibels relative to the maximum power theoretically obtainable by tuning the antenna to each signal. The receiver is designed to operate uniformly as a 400-ohm load at any frequency to which it is tuned.