This Friday 3 pm is open to students (primarily Air Force Institute of Technology, but all invited) presenting a 15 min (or so) talk on what interests them. Open to any & all students, so pass the word. This is a good place for young folks to teach something new to old folks who still like to learn, & / or forgot what it was like to be young. Co-sponsored by: Wright-Patt Multi-Intelligence Development Consortium (WPMDC), The DOD & DOE Communities Speaker(s): Ray Wasky, Agenda: TITLE: Off-azimuth refraction of propagating high frequency (HF) radio waves produced by ‘tilts’ in the ionosphere and the implication for HF over-the-horizon radar (OTHR) operation. ABSTRACT: A state-of-the-art 3-dimensional high frequency (HF) propagation model is used to model the effects of ionospheric tilt, to determine the degree to which off-azimuth propagation exits in the HF band (3-30 MHz). Off-azimuth propagation, where an HF signal travels out of the great circle plane between an OTHR and its intended target region, can create errors in determining the azimuthal position of airborne and surface ship targets, especially if these errors are greater than the azimuth beamwidth of the radar. These errors can vary as a function of transmission frequency, time of day, solar cycle sunspot number, elevation angle, and range to target. Virtual: https://events.vtools.ieee.org/m/321518