Single-Mast Transmit-Receive Antenna for Long-Range 4- 5.5 MHz Coastal HF Radars

TECHNICAL ABSTRACT: The U.S. High Frequency Radar (HFR) network contains more than 140 coastal stations that provide hourly two-dimensional coastal surface currents. Approximately one-third of these are Long Range (LR) systems that transmit in the 4–5.5 MHz frequency band with offshore ranges and resolutions of 160-220 km and 6 km, respectively. Currents provided by this network have numerous applications, most critically Coast Guard search & rescue and oil spill response. LR HFR stations presently require separate transmit and receive antennas, spaced approximately 60 m, which precludes mounting on most buildings or platforms and limits most to ground mounts in areas prone to storm surge. Hurricanes Irene (2011) and Sandy (2012) proved HFR to be a key observation tool, combined with others, to better predict hurricane intensity ahead of landfall. Sandy’s storm surge destroyed part or all of many HFR stations in the Mid-Atlantic, costing tens of millions of dollars to replace and leaving operators to choose between losing hardware or making critical measurements during the next storm. CODAR proposes to build a LR HFR transmit/receive antenna for a single-mast installation on more resilient coastal structures. CODAR will demonstrate this antenna on a weather-hardened Sentinel water level monitoring station in Freeport, TX.SUMMARY OF ANTICIPATED RESULTS: Based on the results obtained in Phase I, CODAR will build a prototype combined transmit/receive antenna for operating in the 4-5.5 MHz band. Texas A&M University will build an autonomous power system and install it on the Freeport, TX Sentinel platform along with a Low Power SeaSonde connected to the new antenna. Performance of the new antenna on the Sentinel will be tested againstperformance on a ground mount as well as against the nearby Long Range SeaSonde installed at Surfside Beach, TX.