High power VLF/LF transmitting antennas - Wheeler´s circuit approximations applied to power limitations

This paper discusses Harold Wheeler´s circuit approximations for electrically small antennas and how they can be applied to transmitting antenna design, particularly to determine the power limitations. The paper includes a discussion of Wheeler´s contributions to the design of the Very Low Frequency (VLF) transmitting system constructed at Cutler Maine, that was the first to achieve 1 MW radiated power in 1961. Wheeler suggested using a cell approach that could be repeated to expand the antenna size as required. The cells chosen for Cutler are diamond shaped flattop panels, a variation of the Triatic antenna. The a single cell of the type used at Cutler was adopted for use as two individual antennas at Fort Collins, Colorado for the National Institute of Standards and Technology (NIST) 60 kHz time signal, WWVB. NIST is considering an upgrade to these antennas. The paper presents a brief description of the VLF antenna at Cutler and the application of updated versions of Wheeler´s methods to the analysis of the WWVB antennas to determine their present and upgraded power radiating capability.