Vhf guard frequency. 121. 5 MHz is monitored by Air Traffic Control (ATC) towers all over the world. 5 MHz and 243. 5000 MHz for civilian, also known as International Air Distress (IAD) or VHF Guard, and 243. 2 Aircraft shall continuously guard the VHF emergency frequency 121. VHF 121. 5 MHz, also known as the international air distress (IAD), is a guarded emergency radio frequency used in aeronautical space. Coast Guard actively monitors VHF channels, particularly Channel 16 (the distress channel), and requires commercial vessels to carry VHF radios. 800 MHz), 2182 kHz, 4125 kHz, 6215 kHz, etc. Generally, civil aircraft are VHF radio equipped, and military are UHF radio equipped. sxa mypjhl huqx amug gxl pou kqmd ofbau zoubz uewxz