A Guide to UHF TV Reception
|Presented by The National Association of Broadcasters, PBS,|
and Stallions Satellite and Antenna
he purpose of this Guide is to provide information for improving UHF television reception in the home. The installation techniques below have been proven with our customer's installations over the past ten years. If followed, you should have a high quality installation that will deliver good TV reception for many years. If you encounter any problems with your TV antenna installation and need technical support, feel free to contact us and would be happy to assist you.
History and Future of UHF TV
Before television first began, the Federal Communications Commission allocated twelve channels for television broadcasting. These channels, 2 through 13, are in the "very high frequency" or VHF band. (Originally Channel 1 was also included, but was soon reassigned to other purposes.)
The tremendous growth in television broadcasting following World War II made it obvious that 12 channels were not enough. So in 1952, the FCC allocated 70 additional channels above the VHF television band and called them "ultra high frequency" or the UHF band. These were channels 14 through 83. Then in the early 1980's, channels 70-83 were reassigned and became cellular telephone frequencies.
In 2009, channels 52 through 69 will be reassigned to uses other than TV broadcasting, due to the rapid growth in portable communication services. The UHF band will not lose 18 TV channels though. These TV channels will be incorporated into the new high definition television (H.D.T.V.) broadcasting standard, which can broadcast up to six digital channels in the same space as one analog channel. Using high definition television, TV stations will be able to broadcast a picture quality that is twice as sharp as the analog broadcasts of the past. Digital broadcasting will also allow adjacent channel spacing of TV channels without creating interference between the two channels, making the broadcasting spectrum more efficient. To see what TV stations in your area are currently broadcasting a digital signal, click here.
UHF signals, due to the physics of radio frequency transmission, are inherently less efficient in the conversion of radio waves to the electrical signals used by the television receiver, and are subject to more losses from some environmental conditions than VHF signals. Good UHF TV reception therefore requires more attention to antenna installation and tuning (on older TV's and VCR's) compared to VHF TV reception. On the other hand, some VHF channels are subject to certain types of interference to which UHF channels are generally immune.
Perfect reception for television signals can't be guaranteed simply because there are too many variables involved. However, by following the recommendations in this guide, the chances for clear reception will be greatly improved.
Improving UHF reception can be a do-it-yourself job. Even if the work is given to a professional, the information in this guide will provide a better understanding of what is needed and what can be expected.
Poor Reception and Poor Antennas
I f UHF reception in general is bad, how it's bad can help determine the problem. "Snow" is visual noise caused by a weak signal, poor antenna system, the set itself, or a combination of these. "Ghosts" or multiple images are caused by a signal arriving from two or more directions simultaneously reflected off buildings, trees and hills. A good antenna system often solves these reception problems. An outdoor antenna is better than an indoor antenna, and an indoor antenna is better than no antenna at all. If an outdoor antenna is needed for good VHF reception, you'll almost certainly need an outdoor antenna for good UHF reception. But if good VHF reception can be obtained with an indoor antenna, a bowtie or other UHF antenna on the TV may also work.
The best indoor antenna
T here are many different types of outdoor antennas available in a wide price range. The type selected is determined primarily by the geographic location of the receiving TV.
Television signals are strongest when the TV station's broadcasting antenna and the home receiving antenna are in line-of-sight. If the line-of-sight is blocked or weakened by hills, buildings or trees, the signal, likewise will be weakened or lost. The signal will also get weaker as it travels farther from the broadcast antenna.
"Gain" is the measure of an antenna's sensitivity-- and its ability to pick up signals. It is measured in decibels (dB). As you move farther away from the TV stations broadcasting antennas, the size of the TV antenna that you will need will increase. Lower quality antennas that claim to be for fringe reception areas often have a long boom, but do not have as many elements as higher quality antennas do. These elements are the actual part of the antenna that capture the incoming signal. The more elements that an antenna has, the more gain it will have, and the more signal it can receive.
Gain can also vary from channel to channel on the same antenna and it can also vary between different antennas. For example, an antenna's gain at Channel 14 may be 8dB, but the gain at channel 69 may be 13dB. These are just a few reasons why it is very important to compare antenna specifications and get the right antenna for the area that you live in.
Where buildings or other obstructions cause "ghosts", an antenna with good directivity is recommended. Directivity is the ability to receive only those signals at which an antenna is pointed. Highly directive antennas have narrow receiving angles (measured in degrees) and high "front to back ratios". These ratios represent the antennas ability to receive signals from the front of the antenna compared to receiving the same signals from the back of the antenna. The higher the front-to-back ratio is on an antenna, the more it will try to reject any unwanted signals from the rear of the antenna. This is especially helpful in areas where adjacent channel interference is a problem or where there are two channels on the same frequency and only one channel is desired. This is called "co-channel interference".
If already have good TV reception on the VHF channels, it will probably be less expensive to add a good quality UHF antenna on the same mounting mast. The separate UHF antenna also will permit pointing to VHF and UHF TV stations which may have their broadcast antennas in different directions from your location.
Pictured is the Winegard HD-9095P UHF Yagi TV antenna with corner reflector (12-16dB gain, for fringe to deepest fringe reception areas with weak signal)
If all television signals are coming from the same direction, both VHF and UHF reception can be improved. Choose an antenna according to the distance to the most distant UHF station for which reception is desired by installing an "all-channel" combination antenna. This is the most common type of outdoor TV antenna.
There are several good quality "all channel" VHF/UHF TV antennas available. If the UHF stations to be received are located in different directions from your house (more than 30 degrees apart):
Rotators are used to turn the TV antenna toward the desired TV station's broadcast antenna.
Pictured is the Channel Master Remote Controlled Antenna Rotator
Antenna rotators consists of two components. The first component is the rotator drive unit (motor). This unit is mounted below the antenna to the supporting mast or tower. The second unit is the rotator control. This unit is located inside usually near the main TV and provides power to the rotator motor through a 3 or 4 conductor wire that runs between the two units.
Once the rotator motor has been mounted below the antenna and the rotor wire has been run and connected to the rotator control inside, all you have to do is program each station's position into the rotor control using the remote. Then it's just a matter of entering the desired TV station's two digit channel number (such as "07" for channel 7) into the rotor's remote control and the antenna turns to the proper position for that channel.
Downlead is a common name for the lead-in line that connects the antenna to the TV. Only coaxial cable, commonly referred to as "coax", should be used for downlead. "Twinlead" (the original brown jacketed downlead wire with two conductors) is a leading cause of poor reception. Twinlead cannot reject interference generated from all types of sources since it is not shielded, unlike coax cable. Good quality coax cable is 100% shielded with an aluminum foil and aluminum wire braiding to reject interference.
Coaxial Cable (Pictured)
As with most products, not all coax cable is made equally. Poor quality coax cable and connectors are one of the leading contributors to poor TV reception. Belden and Comm/Scope are good brands of coax cable to look for, while Thomas & Betts (formerly Augat/LRC) and Gilbert are good brands of coax cable connectors. If you plan on making a lot of coax connections, invest in a coax cable stripper and coax cable connector crimper. These tools that cost around $15.00 each will help you make better connections and could possibly save you time and money later on.
Most combination or "all channel" VHF/UHF antennas have a connection for a single downlead, and in most locations a single high quality coax cable will deliver good VHF and UHF signals. However, a single downlead cannot be connected to both the VHF and UHF 300 ohm terminals on older TV's and VCR's. Instead, a VHF/UHF band separator with an input for coax is required. Connect the downlead coax cable to the input, and the two pairs of wires at the other end to the appropriate VHF and UHF terminals on the TV and/or VCR.
Signal splitters can also reduce signal strength. If you have more than 4 TV outlets connected to your antenna system, there is a good chance that you will need to use a distribution amplifier to improve the picture quality that has been degraded due to the added TV outlets.
An antenna preamplifier, often referred to as a "booster", is used in a weak signal area to amplify or "boost" the TV signal and to help eliminate snow on the TV.
Pictured is a Winegard antenna preamplifier
Preamplifiers consists of two components. The first component is the actual amplifier. This unit should be mounted on the antenna mast about a foot below the main boom of the antenna and is connected to the antenna with a short length of coax cable. The second unit is the power supply. This unit is mounted inside the house and provides power to the preamp through the coax cable between the two units. There should not be any splitters in between the preamp and the power supply. If any splitters are in line between these two units, the splitter may block the voltage from reaching the preamplifier. This will stop nearly all of the incoming signal from reaching the TV.
If a preamplifier is necessary to improve some or all of your TV channels, a few things need to be considered when selecting the right preamplifier for your area. Any TV stations that are strong in signal strength need to be noted. It is possible to amplify these strong stations to the point where they would interfere with the weaker stations that actually need amplification. A preamplifier should be chosen by what channels are weak, and what channels are strong.
Choosing the Best Location For the Antenna
Tips on installation
Connecting Multiple TV's
More than one television (or FM radio) may be connected to one antenna by using a signal splitter. Most splitters weaken signals. Usually if a 2, 3, or 4-way signal splitter is added it will not weaken the signals enough to justify adding a distribution amplifier to the system. If however there are more than four outlets in the house, a distribution amplifier will more than likely be needed. Life Expectancy
Regardless of initial quality, antennas and downlead gradually deteriorate with age. Pollutants and salt ocean air are particularly destructive. If some or all of the channels gradually become weaker over time, then it is a good possibility that the antenna system needs to be looked at, and possibly replaced. Inexpensive antennas will usually last anywhere from 7-10 years, while high quality antennas such as Winegard and Channel Master antennas can last more than 15 years. This is about how long most of the components of a high quality antenna system will last. UHF Channels on Cable TV Cable systems rarely carry a UHF station on its own UHF channel. UHF stations are usually transmitted either on an unused VHF channel or on one of the special cable channels available on a cable-ready TV, VCR, or through a set-top converter furnished to the subscriber by the cable company. The cable company will provide a listing of channels to which the UHF channels have been converted. Occasionally a converted UHF signal will show interference from a strong adjacent channel. If a neighbor of yours who has cable TV has the same problem on their TV, ask the cable company to correct the problem. If you have questions about TV reception problems and solutions not covered on this page, please contact us.
Tips on installation
Connecting Multiple TV's
More than one television (or FM radio) may be connected to one antenna by using a signal splitter. Most splitters weaken signals. Usually if a 2, 3, or 4-way signal splitter is added it will not weaken the signals enough to justify adding a distribution amplifier to the system. If however there are more than four outlets in the house, a distribution amplifier will more than likely be needed.
Regardless of initial quality, antennas and downlead gradually deteriorate with age. Pollutants and salt ocean air are particularly destructive. If some or all of the channels gradually become weaker over time, then it is a good possibility that the antenna system needs to be looked at, and possibly replaced. Inexpensive antennas will usually last anywhere from 7-10 years, while high quality antennas such as Winegard and Channel Master antennas can last more than 15 years. This is about how long most of the components of a high quality antenna system will last.
UHF Channels on Cable TV
Cable systems rarely carry a UHF station on its own UHF channel. UHF stations are usually transmitted either on an unused VHF channel or on one of the special cable channels available on a cable-ready TV, VCR, or through a set-top converter furnished to the subscriber by the cable company. The cable company will provide a listing of channels to which the UHF channels have been converted.
Occasionally a converted UHF signal will show interference from a strong adjacent channel. If a neighbor of yours who has cable TV has the same problem on their TV, ask the cable company to correct the problem.
If you have questions about TV reception problems and solutions not covered on this page, please contact us.
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