What Is Off-air TV Multi-path Interference And
DTV (Digital TV, including HDTV) today is available over-the-air using a standard antenna or via digital cable or satellite. However you receive your TV signal, you will need DTV equipment to decode and view the SD, ED or HD quality DTV programming. DTV equipment today may be purchased as a one or two-part solution. Integrated TV sets are a one-part solution a digital tuner and monitor all in one, just as TVs always have been. A 'HD Ready' TV set will generate a HD picture. But does not have a digital decoder included. The two-part solution consists of a DTV monitor paired with a DTV receiver/set-top box/tuner. The correct digital age off-air (free-to-air) antenna installed and aimed properly with a wide enough beam width (searching area) will receive the desired local stations it's aimed at in range. The more powerful the antenna, the further from the towers the antenna can be located, up to 70 miles or more. This is, provided the antenna has clear line-of-sight to the desired towers. Most TV consumers think of antennas as low-tech devices, but there is more behind some of the newer antenna designs than just bent metal and plastic. Many of the TV antenna designs on the market today such as the Yagi (on many chimneys) and rabbit ears have technology roots going back 30 to 50 years or more. Some people living in the metro/urban areas have a problem to deal with called Multi-path (bounced signals). TV signals bounce off many things, such as buildings, hills, tress (especially Pine trees), even off room walls inside the TV reception room in the case of indoor antennas. Multi-path signals reaching the antenna out of phase (bouncing) can confuse the ATSC (Digital) chip set in the converter box or tuner in digital TV sets. If the signal reaching the front of the antenna is not 2 to 3 times stronger than a bounced signal from the same station reaching the back of the antenna, the ATSC chip doesn't know which signal to use, so it just keeps searching. The answer is to up-grade to a new digital antenna, tuned to receive digital signals and help reject Multi-path signals, one with a high Front-to-back ratio. F/B ratio has to do with the antenna's ability to cope with multi-path signal propagation from the TV station towers to the receiving antenna. The higher the F/B ratio is of the antenna, the better it is with multi-path rejection. The point here, is that the right DTV/HDTV antenna, considering the role reflected signal plays, is not an option, it is now a requirement. Most of the DTV/HDTV antennas returned to retailers are either the wrong antenna for the location or are in perfect working order and returned because of faulty installation techniques. This means there is a huge need to educate consumers and retailers alike about receiving free Off-Air Digital and HDTV signals. For example, in some cases, don't try to 'split the difference' when pointing your antenna between two digital stations coming from different directions. If the broadcast towers are more than 30 degrees apart, use a rotor or separate antennas. When using separate antennas, DON'T MOUNT VHF ANTENNAS (channels 2-6) ON THE SAME MAST, unless they have a 10 foot or more vertical separation, and 6 foot or more vertical separation for channels 7-13). UHF Yagi-style antennas (receiving channels above 13) can usually be mounted with about a 4 foot vertical separation. If you are going to combine signals so that you have only one lead going into your house, use a channel filter for each antenna, so as not to pick up out-of phase signals or multipath through the other antenna. Then and only then you may combine the signals through a combiner (a kind of 'splitter' in reverse). And mount your antenna away from all reflective surfaces or other antennas, and as high as possible. In the suburban area, 8 to 20 miles from the transmitter, a small outdoor antenna will give adequate reception. If the cable from the antenna to the TV set is over 30 feet in length, an antenna booster amplifier will improve reception, particularly on high UHF channels. In rural areas, 20 50 miles distant form the transmitter, a multi-element outdoor antenna equipped with an antenna amplifier can provide good reception in many cases, where the signal is not blocked by terrain (hills, etc.). The switch to digital broadcasts is bringing consumers back to Off-Air reception and the increasing sales are providing the motivation and investments necessary to develop new models and new technology. The fact that most designs on the market now were developed prior to the advent of much of the computer technology, software and algorithms in common use today has left open numerous avenues to improve upon tried and true designs and develop new ones. Additionally, recent regulations and standards are opening new doors for antenna engineers to develop smaller antennas with improved performance, power and aesthetics. With a new digital age antenna, some viewers may still be able to receive their out-of-town channels, carrying locally blacked out sports programs, almost completely uncompressed HD broadcasts (unlike cable or satellite) or network broadcasts not available locally from Cable or Satellite. As an added benefit, an OTA antenna provides reception for second sets in homes not wired for whole-house signal distribution. Depending on the level of desire to receive an excellent picture and multiple broadcast signals, considering the investment in TV entertainment already made by many viewers, they should consider up-grading to a new Digital Off-Air Antenna and loosing the rabbit ears.