The Differences Between Analog & Digital Antennas
- The first television signals were broadcast on the spectrum known as very high frequency or VHF. VHF signal or wave length runs from 1 to 10 meters with a frequency range of 30 to 300 MHz. Television signals occupied the frequencies of 54 to 72 MHZ and 76 to 88 MHz for channels 2 through 6 (VHF-Lo) and 174 to 216 MHz for channels 7 - 13 (VHF-Hi). To receive these signals, antennas were required to have a receptor the same length as the broadcast wave length or about 6 meters for VHF-Lo and around 2 meters for VHF Hi. The several varied length prongs called elements that jut out from the spine-like center post on roof-mounted antennas are cut and folded to lengths tuned to receive these multiple channel wavelengths.
- At the beginning of the 21st century broadcasters across America began converting television signals from analog to digital. By the end of 2007, the FCC-mandated conversion to digital was complete. Although capable of receiving much of the digital broadcast frequencies, analog rooftop antennas are gradually being replaced with digital antennas designed to receive the full spectrum of DTV. These frequencies range upward from the original VHF signal through the majority of the ultra high frequency or UHF band topping out at just about 900 MHz.
- Dish antennas are digital receivers. The signal they are designed to capture originates from an earth station broadcast dish aimed at a communication satellite in a stationary orbit about 24,000 miles above the equator. First suggested by science fiction writer Arthur C. Clark in 1945, the first such satellite was placed in orbit in the early 1960s. As of 2010, hundreds of stationary orbit satellites sit above the equator. They relay a digital signal to the dish antennas of millions of individual subscribers as well as businesses and the military.
- Digital antennas are used on manned and unmanned machines in the ongoing exploration of outer space. Digital signals flow constantly to and from antennas on the International Space Station in low orbit above the Earth. Digital antennas on the twin Martian rovers receive orders from NASA control stations, often several minutes after they are sent due to the vast distances involved. Digital images and other data are returned from the rovers as well as from space probes such as the Galileo, the Voyager and dozens of others traveling millions of miles out in space. Digital antennas operating on military and NASA frequencies also receive images from spy satellites and are even used on the Predator drones that patrol the skies over Afghanistan and the Arabian Peninsula.
