Question 3-70K4

A folded dipole reception antenna is commonly used for aircraft Instrument Landing System (ILS) glideslope reception. Glideslope signals operate in the UHF frequency range (329.15-335 MHz) and are horizontally polarized. A folded dipole is a resonant antenna type that is robust, provides good impedance matching, and has sufficient bandwidth to cover the required frequency range while being sensitive to horizontal polarization when mounted appropriately. Option A is incorrect because ILS glideslope transmissions are horizontally polarized, not vertically. An antenna designed for vertical polarization would have poor reception. Option B, a balanced loop antenna, is generally less efficient for UHF reception compared to dipole variants and is not the standard choice for this application. Option D, an electronically steerable phased-array antenna, is overly complex and expensive for a fixed-frequency reception system like glideslope. Aircraft glideslope receivers use simpler, fixed antennas, as the guidance information is derived from the received signal's modulation, not from antenna steering.