a television station's reception area to , depending on terrain. Analog vs. digital In the previous standard analog television, used before 2006, the VHF and UHF bands required separate tuners in the television receiver, which had separate antenna inputs. The wavelength of a radio wave equals the speed of light (c), divided by the frequency. The above frequency bands cover a 15:1 wavelength ratio, or almost 4 octaves. It is difficult to design a single antenna to receive such a wide wavelength range, and there is an octave gap from 216 to 470 MHz between the VHF and UHF frequencies. So traditionally separate antennas (or on outdoor antennas separate sets of elements on a single support boom) have been used to receive the VHF and UHF channels. Starting in 2006, many countries in the world switched from broadcasting using an older analog television standard to newer digital television (DTV). However generally the same broadcast frequencies are used, so the same antennas used for the older analog television will also receive the new DTV broadcasts. Sellers often claim to supply a special "digital" or "high-definition television" (HDTV) antenna advised as a replacement for an existing analog television antenna; at best this is misinformation to generate sales of unneeded equipment, at worst it may leave the viewer with a UHF-only antenna in a local market (particularly in North America) where some digital stations remain on their original high VHF frequencies. Reception issues Places unable to be reached by television broadcast transmitters are known as "black spots" in Australia. In East Germany, the areas that could not receive western TV signals were referred to as the Tal der Ahnungslosen, or "Valley of the Clueless". Indoor Indoor antennas may be mounted on the television itself or stand on a table next to it, connected to the television by a short feed line. Due to space constraints, indoor antennas cannot be as large and elaborate as outdoor antennas, they are not mounted at as high an elevation, and the building walls block some of the radio waves; for these reasons, indoor antennas generally do not give as good reception as outdoor antennas. They are often perfectly adequate in urban and suburban areas which are usually within the strong radiation "footprint" of local television stations, but in rural fringe reception areas only an outdoor antenna may give adequate reception. A few of the simplest indoor antennas