The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is a proposed mission designed to observe ultra-high-energy cosmic rays and cosmic neutrinos using space-based measurements of extensive air showers. A precursor to this mission is POEMMA Balloon with Radio (PBR). Scheduled for launch in 2028 from Wanaka, New Zealand, PBR will operate at a suborbital altitude of approximately 33 km. Through the combined use of multiple instruments, PBR will enable a multi-wavelength study of air showers. Its payload features a fluorescence camera, an air-Cherenkov camera and a radio instrument triggered by the latter. The radio instrument consists of two dual-polarized receiver channels equipped with broadband sinuous antennas sensitive in the $60-500\,$MHz band. This radio instrument is essential to achieving one of PBR’s science goals: the detection and characterization of the radio emission of High-Altitude Horizontal Air Showers (HAHAs) which are inaccessible to traditional ground-based detectors. The simulation of radio emission from HAHAs is performed using two independent software packages, CoREAS and ZHAireS-RASPASS. This contribution presents an overview of the PBR mission and its radio instrument, and details the ongoing preparatory analysis focused on characterizing the expected radio signals from the HAHAs that PBR aims to detect.