|Antenna Hookup over-the-air digital and analog TV|
Home wiring for over-the-air digital TV
After Feb. 17, 2009 most over-the-air TV broadcasts in the USA are going from analog to digital. The UHF (TV channels 14 to 69) and some VHF (TV channels 2 to 13) frequencies are still going to be used just like before but the signals will be in a digital format. This means old analog TV sets cannot pickup the signals directly because they have a built-in NTSC tuner. What is needed is an ATSC tuner which is what the digital TV sets have built in them. Buying a converter box allows you to continue using your old analog TV set because the box will receive the ATSC digital signals and convert them to NTSC so your analog TV can use them. Your old analog TV set will however not be able to show High-Definition video. It will max out at 480 lines of resolution which is what the typical CECB converter box outputs. High Def is 720 or 1080 lines of resolution. Your analog TV set will still be able to display VHS tapes from a VCR or DVD from your DVD player just like before.
What's new with digital TV:
Your old TV antenna may be all you need to get digital TV stations, particularly if you live in a large city. However, if you live more than 60 miles from the TV transmitting tower of a local TV station, you may find it difficult to get a signal strong enough to display on your TV. Even if you live well within the limits of TV transmissions, you may need to get a new TV antenna for the best reception. You may be able to pickup local TV stations with a simple indoor rabbit ears antenna just like before. There is nothing substantially different from the old VHF/UHF antennas and any new, so-called digital or HDTV antenna because the same basic UHF and VHF antennas are used. Yes, you can get High-Definition TV shows with a UHF (VHF) antenna. If you live within 20 miles of the TV tower, you may get away with using an indoor antenna. Any further away, you will most likely need an outdoor antenna.
Important antenna concepts to understand:
TV antennas are not all the same. There are TV antennas designed to pickup UHF signals and there are TV antennas designed to pickup VHF signals and there are TV antennas designed to pickup both UHF and VHF signals. Some TV antennas are highly directional while others are more non-directional. It is important to know where your TV station's transmitting tower is in relation to your antenna's location. Go to www.antennaweb.org and www.tvfool.com to find out where your local TV towers are located, what local TV channels you have and to find out about what kind of antenna you are likely to need.
There are many factors which determine how well you receive local over-the-air TV signals. These include but are not limited to:
o Your location - distance from TV transmitting tower and objects between TV tower and your antenna such as hills, trees, buildings.
o TV station's transmission power output.
o Your antenna - type, size, height, location and direction.
o Type of Cables from antenna to TV.
o Splitters in use for multiple TV sets which result in loss of signal strength.
o Signal amplifiers and distribution units.
Rotors (antenna rotators, motorized antenna aimers) - When a highly directional antenna is employed, a rotor becomes necessary when the desired stations are in multiple directions. A remote controlled rotator allows the user to "aim" or move the antenna in the direction of the desired TV station for better reception. Typically you can move the antenna in a circle about 360 degrees using a motor mounted to the antenna mast. You control the motor from inside the house. Wires connect the motor to an inside unit which can be remote controlled by the user.
A rotor is a minor nuisance for analog stations, but it becomes a major problem for digital stations. This is because it takes 10 times longer to discover the correct aim for a DTV station. For weak stations it can take up to 10 minutes to achieve the optimum aim.
For an ideal rotor, the antenna would always point where the indoor controller indicated. Some rotors suffer “creep”, a small directional error accumulation. The creep can build up during the short jerky movements typical during station searches, and soon the antenna is pointing far from where the dial said, making the dial calibrations useless.
The Channel Master rotor has an infrared remote control. This rotor doesn’t suffer as much creep. But it can creep. The controller has a microprocessor that counts the number of times the rotor is used. After a certain number, the controller will recalibrate to eliminate the accumulated creep. It does this by rotating the antenna to the limit in one direction, then to the limit in the opposite direction, and then to the requested channel direction. If you must have a rotor, get one that is capable of this correction.
If your stations are in just two directions, you will be happier with two antennas. A common splitter can be used to combine the two antennas. Doing this will cost you a lot of signal strength (Half of the signal from each antenna gets rebroadcast out the other antenna. Figure a 3.5dB loss at the splitter.). A Join-Tenna is a device that can avoid this loss.
Another way to avoid the 3.5 dB loss is to use an antenna switch to combine the two antennas such as the Radio Shack 15-1968 switch, which has an infrared remote control.
Splitters/Combiners/Diplexers - A splitter is a sort of “Y-adapter”. All splitters are bi-directional, and thus will serve also as combiners (watch out for interference). These devices are usually 85%-95% efficient, whether used as splitters or combiners. There are four basic types. They look almost identical, but are very different devices.
50 MHz - 900 MHz splitter/combiner - Commonly available in 2-way, 3-way, 4-way, and 8-way types, this is the splitter you want if you have multiple TVs or want to gang two identical antennas. The splitter is designed so that it will not cause reflections, but if you leave an output unconnected then there will be reflections. If a 2-way splitter were 100% efficient, you would figure a 3dB loss since each TV would get half the power. Some splitters incorporate a DC Block in one output so that the splitter can be between an amplifier and its power injector.
900 MHz - 2200 MHz splitter/combiner - These can be used with satellite systems, but be sure you know how control issues will be resolved.
VHF/UHF splitter/combiner - This device will split UHF off from the VHF, which would be necessary for TVs with separate VHF and UHF inputs. The device will also combine a VHF antenna with a UHF antenna. The advantage of this splitter is that there is no 3dB loss. (Technically, this device should be called a diplexer.)
Satellite/OTA diplexer - This device will allow a satellite dish and an over-the-air antenna to share the same cable. The loss in the device will not be 3dB, but there will be some small loss. Check for whether DC is blocked to the OTA port. Satellite/OTA diplexers will not work with the new 5-LNB dishes from DirecTV.
Note: Splitters in cable TV systems with “on demand” features must pass 5 MHz - 900 MHz.
Choosing the proper antenna for your setup.
With the information obtained from the above two links, you should know where your TV stations are in relation to your home antenna. You should be able to determine if your TV stations are primarily located in the same direction or in many directions and how far away they are from your home antenna. Based on this data, you need to decide if you need an antenna which is good for 20 miles, 30 miles, 40 miles, 60 miles and if it should be UHF, VHF or both. Buy from a known antenna source such as Winegard, Channel Master or their authorized retail dealers. www.winegard.com offers locators for dealers in your area.
Signal Amplifiers, Preamplifiers
If your TV signal is too weak to get a good picture, you could try a good signal booster, amplifier.
There are two types of signal amplifiers:
(Mast-mounted amplifiers) - These should be mounted as close to the antenna as possible. Usually the amplifier comes in two parts:
1. The amplifier. This is an outdoor unit that is normally bolted to the antenna mast. It must have a very low noise figure, and enough gain to overcome the cable loss and the receiver’s noise figure.
2. The power module (power injector). This is an indoor unit that commonly lies on the floor behind the TV. It is inserted into the antenna cable between the amplifier and the TV. This module injects some power, usually DC, into the coaxial cable where the amplifier can use it. The power injector is the amplifier’s power supply.
Distribution amplifiers - These are simple signal boosters. They are often necessary when an antenna drives multiple TVs or when the antenna cable is longer than 150 feet. Distribution amplifiers don’t need to have a low noise figure, but they need to be able to handle large signals without overloading. Commonly, distribution amplifiers have multiple outputs. Some handle up to 8 TV sets and many can be connected together so that many more TV sets can be handled. There are also components which allow you to control your media room's gear (satellite receiver, VCR, DVD player) from other rooms in the house where a TV set may be located, by IR remote so that you do not have to leave a room in order to change channels for example.
There should always be a long cable between the preamplifier and any distribution amplifier. Placing the two amplifiers close together can cause overload and/or oscillation.
A mast-mounted amplifier’s most important characteristic is its noise level.
Noise level -- Rating
0.5 dB -- superb
2.0 dB -- excellent
4.0 dB -- fair
6.0 dB -- poor
The noise figure is a number you must subtract from the antenna’s gain. The noise figure tells how much of the antenna’s gain you are throwing away.
The cables used to connect antenna to TV and antenna to pre-amp, splitters and the like is called RF coaxial RG-6 cable. It has a center wire, usually copper, and outer insulation all wrapped in a flexible plastic housing. The ends typically use what is called an "F" connector and the connector typically screws on to the jack (In or Out).
o Example setup for a home with over-the-air broadcast TV.
Local channels not available with satellite service.
Channel Master 4228-HD antenna from solidsignal.com
The Channel Master 7777 preamplifier has separate inputs (and separate amplifier circuits) for VHF and UHF, which are then combined without loss. There is a switch inside that will allow VHF and UHF input via the same connector. The unit usually comes with the switch in the “separate input” position. A second switch disables the FM trap. You have to remove the 4 base screws to access the switches.
If you add a good amplifier to your antenna system and your results get worse instead of better, then you have signal overload and you need to rethink your setup.
An RF splitter can be reversed to form a signal combiner. As long as only one source is "active" at a time, there will be no interference. Turn off the satellite receiver when viewing over-the-air channels and when viewing satellite channels, turn off the DTV converter box. This way you can use the respective remote controls for the boxes and you will not have to get up from your easy chair to switch an A/B switch each time you want to change from satellite to local channels or locals to satellite.
Decibels - Decibels (dB) are commonly used to describe gain or loss in circuits.
UHF - The Ultra High Frequency spectrum is everything from 300 megahertz to 3.0 gigahertz. One of the bands within this spectrum is the TV UHF band, which goes from 470 megahertz (channel 14) to 806 megahertz (channel 69). Each of these stations occupies 6 megahertz of that spectrum.
VHF - The Very High Frequency spectrum is everything from 30 megahertz to 300 megahertz. It is divided into many bands for different purposes (police, fire, aircraft, etc.) Two of the bands within VHF are:
1. The TV VHF-low band. This band goes from 54 megahertz (channel 2) to 88 megahertz (channel 6).
2. The TV VHF-high band. This band goes from 174 megahertz (channel 7) to 216 megahertz (channel 13)
Each channel occupies 6 megahertz of this spectrum. (There is a 4 MHz gap between channels 4 and 5.)
8-Bay antenna - This is a stacked dipole reflector antenna. Its searchlight-like beam makes it very different from the 4-Bay. This highly directional high gain antenna is commonly thought to be the strongest overall UHF antenna. 8-Bays are made by Channel Master, Winegard, and Antennasdirect.com . The Winegard 8-Bay is skewed in favor of the low channels, and is presently the best antenna available for channels 14-30. (If you want an antenna skewed in favor of the high channels, select a big Yagi/Corner-reflector.) 8-Bays are roughly 40”x36”. 8-bays are intended only for UHF. However the Channel Master 8-bay will pick up channels 7-13 quite well.
Grounding outdoor antennas
For TVs, the main benefit of grounding is lightning protection. A lightning strike in your neighborhood can generate thousands of volts on the coaxial line. These voltages can damage your equipment.
To reduce these voltages the antenna cable should have a grounding block (Radio Shack 15-923) at the point where it enters the house, and that grounding block should be wired to a ground rod driven into the ground as close as possible to the grounding block. An effective ground rod is one driven deep enough to reach into moist soil.
The ground rod should also connect to the mast via a heavy wire. #8 aluminum wire is readily available for this. Ground wires should be as short and straight as possible. Turns should be curves with a 6-inch radius. Ground wires do not need insulation.
Stores and websites supplying antenna equipment
The following manufacturers’ websites have store locators:
· Channel Master ( www.channelmasterintl.com )
· Winegard ( www.winegard.com )
· Antennacraft ( http://www.antennacraft.net )
· Radio Shack ( www.radioshack.com )
The following manufacturers sell online:
· Antennasdirect.com ( www.antennasdirect.com ) A.k.a. Terrestrial Digital
· Radio Shack ( www.radioshack.com )
· Warren Electronics ( www.warrenelectronics.com ) (Channel Master, Winegard, Antennacraft)
· Stark Electronics ( www.starkelectronic.com ) (Channel Master, Winegard, Antennacraft)
· SummitSource.com ( www.summitsource.com ) (Winegard, Antennacraft, Channel Master)
· SolidSignal.com ( www.solidsignal.com ) (Channel Master, Winegard, Antennacraft, AntennasDirect)
· TV Antenna Source (www.dennysantennaservice.com) (Winegard)
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