TV DX and FM DX is the active search for distant radio or television stations received during unusual atmospheric conditions. The term DX is an old telegraphic term meaning "long distance."
VHF/UHF television and radio signals are normally limited to a maximum "deep fringe" reception service area of approximately 40–100 miles (64–161 km) in areas where the broadcast spectrum is congested, and about 50 percent farther in the absence of interference. However, providing favourable atmospheric conditions are present, television and radio signals sometimes can be received hundreds or even thousands of miles outside their intended coverage area. These signals are often received using a large outdoor antenna system connected to a sensitive TV or FM receiver, although this may not always be the case. Many times smaller antennas and receivers, such as those in vehicles, will receive stations farther than normal depending on how favourable conditions are.
