VHF Omni-directional Radio Ranges [VORs] operate in the Very High Frequency aviation navigation [NAV] band between 112.1 and 117.9 MHz. As VHF transmissions are line-of-sight the ground to air range depends on the elevation of the beacon site, the height of the aircraft and the power output. The VOR beacons are usually located at airfields but as they serve to define designated air routes [ airways] some are located away from airfields, often on high ground.