ardf events use radio frequencies on either the 2-meter or 80-meter amateur radio bands. these two bands were chosen because of their universal availability to amateur radio licensees in all countries. each band requires different radio equipment for transmission and reception, and requires the use of different radio direction finding skills. radio direction finding equipment for eighty meters, an hf band, is relatively easy to design and inexpensive to build. bearings taken on eighty meters can be very accurate. competitors on an eighty-meter course must use bearings to determine the locations of the transmitters and choose the fastest route through the terrain to visit them. two meters, a vhf band, requires equipment that is relatively more complicated to design and more expensive to build. radio signals on two meters are more affected by features of the terrain. competitors on a two-meter course must learn to differentiate between accurate, direct bearings to the source of the radio signal and false bearings resulting from reflections of the signal off hillsides, ravines, buildings, or fences. large national or international events will have one day of competition using a 2-meter frequency and one day of competition using an 80-meter frequency.