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Article is courtesy DTVMAX.Com
In the final days of 1996, the Federal Communications Commission (FCC) approved the digital television broadcast standards for the United States. Although these standards only apply to conventional over-the-air terrestrial broadcasts, it is likely that cable and satellite television delivery systems will also support these same standards. All DTV broadcasts will be on UHF channels and the current analog TV broadcast, and all VHF television broadcasts, will be phased out at the end of 2006 (just 8 years away). While the FCC standards do not specify the video resolution modes for the DTV, the manufacturing group (i.e., the so called 'Grand Alliance') that drafted the proposal to the FCC included 18 combinations of resolution, scanning rates and scanning mode. The highest resolution mode proposed was 1920 X 1080 pixels. This mode uses 'interlaced' scanning, as does today's analog TV. With interlaced scanning the odd numbered scanning lines (i.e., lines 1, 3, 5, etc) are displayed in the first 1/60 second and the remaining even numbered lines are displayed in the next 1/60 second. By combining these two 'fields' one complete frame of the video is displayed every 1/30 second. Some of the standard and medium resolution DTV modes use progressive, or non-interlaced, scanning. In this mode all of the scanning lines are displayed sequentially (i.e., 1, 2, 3, 4, 5, etc.). This is the method used in modern computer displays and generally produces less flicker in the displayed image and smoother motion for video (if a live or taped broadcast originally recorded in progressive 60 Hz mode). The letter "I" or "P" will frequently be included along with the resolution number. For example a HDTV set's specification sheet (or advertisement) may indicate that it supports 1080I, thus indicating this is a 1920 by 1080 resolution 'Interlaced' mode. Also the number of frames per seconds may be varied with 24 (used for film sources), 30 and 60 frames per second being allowed. Note that these are the transmitted frame rates and a given TV receiver may actually refresh the display at a higher rate.
The proposed DTV standards allowed both standard resolution modes, with about twice the horizontal resolution of conventional analog broadcasts (similar to that provided by DVD or Directv), as well as medium and high definition TV (HDTV) modes. There are 18 different broadcast modes defined with the lowest resolution being 480 by 640 pixels and a conventional 3 by 4 screen aspect screen ratio (i.e., picture width is 33% wider than picture height), as used in today's analog television sets and computer monitors. There are standard definition modes defined using 3 by 4 aspect ratio as well as the widescreen 16 by 9 ratio. However, all of the medium and high definition modes use the widescreen 16 by 9 screen ratio. The FCC has specified that the video will use MPEG-2 digital compression for the video and the audio will be encoded using Dolby Digital, with 5.1 channels. Both of these techniques are already in use in other consumer home theater products. MPEG-2 is used by satellite TV providers, including Directv and Disk Network, as well as with DVD systems (although at a resolution equivalent to the low-end of the DTV values - i.e., standard definition DTV). Dolby Digital encoded audio is the same as currently used on DVDs and some Laserdiscs. Broadcast television stations converting to DTV, can offer 4 (or perhaps even 5) simultaneous standard definition programs in the same channel bandwidth required for either a single existing analog channel or for a single HDTV program. Since DTV will operate at about 4 times the data rate of DVDs or Directv the picture quality of a standard definition DTV broadcast should be similar to, or somewhat better than DSS. The highest resolution HDTV mode offers a picture that is 1920 pixels wide by 1080 pixels high. It is this high definition mode that is of most interest to quality conscience home theater owners. Somewhat lower resolution modes, using progressive (i.e., non-interlace) scanning are also considered high definition. However, any television set claimed to be a "High Definition Digital Television" must support reception of all 18 modes AND must display images at the highest resolution mode (i.e., 1920 X 1080). Other less sophisticated televisions may be sold that may receive all 18 modes but will down-convert the highest definition modes for display at lower resolution. To confuse matters even further some sets that can be called HDTV capable are not actually able to display the full 1920 pixels in the horizontal direction. For CRT-based projection TVs, 9 inch diameter projection tubes using magnetic focus and when combined with high quality electronics and optics are required to display the full 1920 pixel horizontal resolution. However, high quality projectors using magnetically focused 8" projection tubes can come very close to projection the full HDTV resolution displaying up to 1600 horizontal pixels. Typical projectors using 7" projection tubes are usually limited to 800 to 1000 horizontal pixel resolution For the moment no LCD, DLP nor plasma display has adequate resolution to qualify as being capable of displaying the full resolution of the 1080I HDTV mode. However the best LCD projectors (see Sony listing below) can now fully support the 720P HDTV mode. Additional LCD and DLP high definition projectors (for the 720P mode of HDTV) are expected during the latter half of 2000. JVC already has D-ILA technology projectors that supports the 720P HDTV resolution. I have attempted to include valid information in the table below, but assume no responsibility for the accuracy of the information. Also note that many new models are being added and prices are frequently changing (generally downward). Visit the manufacturers web sites (by click on the manufacture link provided below) to check for the latest information on their current DTV models. For the following chart the models indicated by green shading are considered to support HDTV. This means this model supports 16X9 widescreen display and is capable is actually displaying approximately 1 million pixels (or more). This corresponds roughly to the resolution of the 720P HDTV format or displaying the 1080I format at about one half the resolution that format is capable of. Check out http://www.dtvmax.com/dtv.htm for avaiability.
Article is courtesy DTVMAX.Com
Virtually all data and graphics grade video projectors sold over the last two decades have offered a RGB (red-green-blue) style video input. This could be used with a external computer for displaying computer graphics output to an audience or with a external line doubler to displaying enhanced video. RGB connectors come in two different common forms. The first is a standard VGA connector common with virtually every PC, desktop or laptop computer. Cables using VGA connectors employ a single 15 pin connector with a multi-conductor cable to carry the RGB and sync signals from the source (i.e., line doubler or PC) to the display (e.g., video projector). While VGA connections are high bandwidth and are suitable for HDTV use, the relative high-loss cable typically used generally limits the cable length to about 10 feet. The second type of RGB connection uses separate coax cables, each approximately 0.2 inch in diameter, to carry the RGB plus vertical and horizontal sync. signals. Generally this involves 5 discrete coax cables each terminated with a BNC type connector. Harnesses are available where the five discrete coax cables are physically bundled together for convenience. BNC connectors are widely used for professional applications. RGB video cables using such discrete coax cables terminated with BNC connectors are relatively low loss and work well for extended cable runs (e.g., typically available in cable lengths up to 50 feet (or more). Also adapter cables are readily available with a VGA connector on one end and discrete BNC terminated connectors on the other end. This allows the flexibility to interconnect DTV receivers and video projectors, or monitors, that uses a VGA style connector for one device with the other device using BNC connectors. Several HDTV manufactures ( e.g., RCA, Mitsubishi, Sharp, etc.) have adopted RGB style, either in the form of VGA or discrete BNC connections, for the interface between the projector/monitor and the DTV receiver box.
While RGB is technically one type of component video interface, the term 'component video' in the world of consumer DTV/HDTV equipment usually refers to an altogether different type of video interface. With the DTV/HDTV 'Component Video' format the luminance (i.e., black and white video) information is separated from the chromance (color) information. The chromance information is then further separated into two differential signals where the red, green, blue components are added and subtracted from one another. Component video uses three external output connectors (using standard phono, or RCA style connectors). Toshiba introduced component video to the consumer video world with their first generation DVD players and a projection TV set using compatible component interface. While this original version introduced by Toshiba for their DVD players and TVs is not compatible with HDTV standards, Toshiba now offers an enhanced version, suitable for HDTV and a number of other DTV manufactures have also adopted compatible component video interfaces.. The various consumer DTV manufactures use a variety of terms to describe the component video interfaces. The common terms are: component video, HD-Colorstream (Toshiba), YCrCb, YPbPr or YPrPb. All of these terms refer to an identical type of component video interface. Some DTV manufacturers (e.g., Mitsubishi) have decided to support both RGB as well as component video interfaces on their DTV monitors/projectors.
The bottom line is there are two incompatible types of interfaces between DTV projectors/monitors and DTV set top receiver boxes. Therefore the consumer must be very careful with mixing brands for their DTV projectors/monitors and the DTV set top receiver boxes. The set top receiver box must support an output interface compatible with the projector/monitor input. To further complicate the mixing and matching of set top receiver boxes and DTVs some DTV manufactures also provide an additional interface between the receiver and the DTV projector/monitor that allows the receiver to control the settings of the DTV projector/monitor. One specific example is Mitsubishi whose first generation DTV projectors used an RGB interface that required their own receiver be used to control the projector/monitor. However the new second generation Mitsubishi projectors will interface with DTV set top receiver boxs using RBG, component video or the Mitsubishi box that uses RGB plus control interfaces. The table above of DTV projectors/monitors lists the type of DTV interface(s) supported. Note that some DTV sets support both RGB/VGA and Component Video interfaces. Likewise some HDTV set top boxes also support both types of interfaces. However be certain to check this out before you make your purchase. Monster Cable and Current Design have announced transcoder boxes to convert conponent video to RGB but these are expected to be rather expensive. However a low cost VGA input to component video output transcoder box (model 9A60) is now available from Audio Authority (phone 800-322-8346). I have not seen this unit, therefore can offer no opinion of its performance. However the price is right at just $129 and may be just the thing for owners of projection TVs with only component video inputs for HDTV to connect to the already available RCA DTC-100 DTV/DirecTV receiver's VGA output.
DTV Set Top Receiver Boxes
Article is courtesy DTVMAX.Com
See the table above for information on HDTV receiver set top boxes (STBs) designed for use with HDTV compatible TV monitors and projectors. A few additional HDTV receiver boxes are planned that are not being sold in conjunction with specific models of HDTV monitors or projectors. Of all of the set-top HDTV receiver boxes the most interesting (because of it announced price) is the RCA DTC100 receiver that features a true HDTV output (i.e., 1080I format) using an SVGA type RGB output and including an integrated DirecTV satellite receiver that can handle regular and HDTV DirecTV channels. This STB should be on RCA dealers shelves by September (as per Thomson press release of 19 August 1999). This STB will also include S-video and composite video outputs for use with conventional analog TV monitors and projectors. See photo below of the DTC100's rear panel. The DTC100 does not upconvert the standard definition DTV(e.g., 480I, 480P, etc.) formats to 1080I as do some other DTV receivers. Rather the RCA/Proscan STBs will convert standard Directv programming, standard analog broadcasts, and the standard resolution DTV formats of to a non-standard format of 540P. This will results in the same scan rate of the standard HDTV format on 1080I and any HDTV monitor with a VGA or RGB input that can handle 1080I should also be able to handle 540P. However, the DTC100 does upconvert the scond high definition format 720P to 1080I for output via the VGA port . The RCA/Proscan STBs will receive and output 1080I broadcasts and HD-Directv programming in 1080I format. Thus a TVs/monitors connected to the STB's RGB (VGA) output will always be handling the same horizontal and vertical scanning rates for all received signal formats (i.e., 60 Hz. vertical rate and 32.4KHz horizontal rate). This bargain HDTV receiver (RCA DTC100 and similar Proscan PSHD105) is priced at a very reasonable $649 (suggested list price). The DTC100 user's manual can be download from the RCA DTC100 web page. One item to note is the DTC100 uses slightly non-standard values for some of video synchronization signals may may require a minor adjustment of the horizontal picture width and horizontal position on the monitor or projector. A new 18 inch by 24 inch elliptical shaped satellite dish, model DSA-8900 ($200) is required to receive the HDTV DirecTV channels than are coming from new satellites located at a different orbit position than the current DirecTV satellites. The new dish will receive signals from both the current satellites as well as from the new satellites. The new dish is an extra cost item unless you purchase a DTC100 in combination with an RCA DTV, in which case the dish is being provided at no extra cost (at least for a limited time). Mitsubishi and Toshiba have each recently announced similar DTV/DirecTV integrated receiver STBs. The Mitsubishi unit (model SR-HD500) will go on late late in 1999. Mitsubishi has not yet announced a price. The Toshiba unit, model DST-3000 offers similar features as the RCA/Proscan units except it will upconvert all analog and digital broadcast and Directv formats to 1080I HDTV format for out to the TV/monitor. Expect this unit to sell for approx. $1000 when it goes on sale in late 1999. Panasonic has upgraded their DTC STB to now offer both component and RGB outputs and they have lower the price from $1700 to $1000. Look for the new model TU-DST51 if buying a Panasonic STB.
Several companies have been talking about set-top boxes to receive the DTV broadcasts and to convert them to analog for display on current analog TV sets. These converter boxes are not for use with HDTV sets and will initially sell for $600-$700 when they go on sale in late 1999 (note the RCA receiver mentioned above will have this capability and be available in October 1999. The idea of these boxes is to extend the life of you expensive analog TV set by allowing you to receive digital broadcasts. The picture quality should be similar to that from a digital satellite system displayed on the same analog TV set. That is, probably better than the reception of normal analog TV broadcasts but not as good as having a standard definition DTV set and not nearly as good as having a true HDTV capable DTV set (when receiving a HDTV broadcast). Zenith also announced a joint project with Intel to develop a HDTV receiver on a PC card. Also expect ATI to be offering a HDTV tuner on a card for your PC.
The following table provides a quick summary of the HDTV Set Top Receiver Boxes currently available and planned for 2000 and the type of DTV output(s) they offer to connected to a DTV projector/monitor. Note that a number of manufacturers have announced new models for introduction in 2000 that include integrated DirecTV Plus receivers capable of receiving HD channels offered via DirecTV (also requires a new dish).
Article is courtesy DTVMAX.Com
100+ DTV stations are now on-the-air (see list of DTV at http://www.dtvmax.com/dtv.htm . CBS, NBC, ABC and/or FOX began DTV broadcasts in the 10 following U.S. market areas: Atlanta, Boston, Chicago, Dallas, Detroit, Los Angeles, New York, Philadelphia, San Francisco, Washington in lat 1998. Both CBS, NBC & PBS are supporting the 1080I (1920 X 1080 interlaced) high definition mode. CBS hasl begin broadcasting 15 to 20 hours per week of their prime-time TV programming in true 1090I HDTV format. NBC will carry some prime time programming and the Tonight Show is now broadcast in HDTV. ABC is now broadcasting NFL Monday night football games in HDTV. For Standard Definition TV (SDTV) CBS broadcasts will use the 480 line interlaced format while NBC will use the 480 line progressive scan format.. ABC is using the 720 line progressive scan mode for HDTV, but some local ABC stations are converting the network 720P feeds to other formats for their transmissions. ABC is using the 480 line progressive scan mode (480P) for its SDTV broadcasts. The 10 market areas for the initial DTV broadcasts are expected to grow to 25+ market areas by the end of 1999. A shortage of broadcast equipment, including transmitters for DTV stations, will likely inhibit the nationwide availability of broadcast DTV services. Directv has begun two dedicated channels of pay-per-view HDTV programming by the with the HD-HBO channel now offering about 75% true 1080I format HDTV programming during prime time. Also Showtime has begun an HD channel that is currently carried by Dish Nework along with HD-HBO. This means national availability of HDTV programming is now available, not just in the cities where over-the-air HDTV stations are operational. The HDTV DirecTV service will be via new satellites located in a different orbital slot from the current DirecTV satellites. This means that to receive these HDTV DirecTV channels you will need a not only a new DirecTV receiver but also new DirecTV dish. The new dish is an elliptical shape that is 18 inches by 24 inches. This dish uses dual pickups (and LNB) in order to receive from both the existing and the new DirecTV satellites. Thomson HDTVs (RCA, GE and Proscan) will include the decoders for receiving both off-the-air broadcasts and for receiving HDTV from DirecTV (i.e., DirecTV). Several other manufactures (e.g., Toshiba) have now signed up to offer HD-DirecTV receivers by early-to-mid 2000. All of the broadcast networks have indicated they have no specific plans for multi-channel standard definition broadcasts during periods when high definition broadcasts are not underway. However such a decision will likely be up to the individual TV station owner rather than the network. Also expect to see the arrival of DTV compatible VCRs supporting HDTV recording and playback during 2000 (Panasonic already has a model available for $1000 that works only with their HDTV set top receiver box). This first generation of Digital VCRs will be VHS-based using SVHS tapes (this format will be called DVHS). Expect this to be an interim solution until either re-recordable DVD optical disks become widespread or the transition to another digital video tape format takes place.
Now for the bad news concerning DTV and cable TV. The cable TV industry has been very late in deciding what to do about DTV and especially HDTV. They have only recently agreed on an interface to be included on new digital cable TV boxes (uses IEEE 1394). You will need a compatible interface on your DTV receiver (either built into a DTV set or in an outboard DTV receiver box). The first and second generation DTV sets and receiver boxes do not have this interface. These current units will not be compatible with digital cable TV boxes when they appear. Therefore, if you rely on cable TV for your programming, you had best wait until the their generation DTV sets and receivers arrive (perhaps by late 2000). It will be up to your local cable TV company to decide when they will offer the new cable boxes and begin to carry the HDTV HBO and Showtime channels and DTV broadcast channels.
Article is courtesy DTVMAX.Com
The introduction of broadcast DTV service has prompted some manufacturers to start offering TV antennas, at premium prices, that are being advertised as being designed specifically for reception of DTV broadcasts. In fact, there is nothing truly unique about these antennas that make then more capable of receiving DTV broadcasts as compared to any well designed TV antenna manufactured before the advent of DTV. However, the characteristics of DTV receivers (i.e., TV set or set-top-box) do differ from those of analog TV receivers. With analog receivers the TV video (picture) and audio will slowly degrade as the quality of the input signal degrades. With digital receivers the input TV signal can degrade up to a certain point without any effect on the video or audio but beyond this point any further degradation in the broadcast signal will cause the video and audio to quickly deteriorate, with such symptoms as momentary loss of audio and frozen video images, until the video and audio are totally lost. Generally these differences in the reception characteristics of analogy vs. digital TV signals need not impact the requirements for an antenna system capable of delivering a good picture. However, if your current TV antenna system provides anything less than a good video for analog broadcast reception (i.e., snowy picture or a picture with heavy ghosting) then it will probably not be adequate for DTV reception. The basic requirements for the successful reception of any analog or digital TV broadcast are:
Achieving adequate Signal Strength &endash; This factor can either be an issue or a non-issue for you depending a several factors. Certain factors must be considered the givens for your specific case (i.e., those factors that are outside of your control). The most obvious of these are the proximity of your location to the transmitter location of each TV station you are attempting to receive, the power of the TV stations transmissions, and the geography/obstructions between your location and the TV stations transmitter. The four factors that are under your control that will influence the signal strength provided to your TV receiver are the type of antenna you use, the location of your antenna, the orientation of your antenna, and your signal distribution system from your antenna to your TV receiver. See the discussion below on each of these factors.
Achieving adequate signal to noise ratio &endash; This factor is best addressed by first selecting, locating, and orienting a TV antenna to provide adequate signal strength at the antenna terminals then using quality, low loss TV cables and amplifiers (as necessary) to keep the signal well above the signal levels of the electrical noise. See the discussions below on selecting, locating and orienting the TV antenna and on designing a signal distribution system.
Achieving Freedom from Multipath &endash; With analog TV multipath shows up as ghosts in the TV picture. As the term multipath implies, this is the condition where you are receiving the TV signal via the most direct path from the TV stations transmitter and you antenna, and you also receiving the TV signal via one or more additional paths where the signal has been reflected off of such things as buildings, airplanes, etc. In some cases multipath can be very difficult, or impossible to totally eliminate. With DTV signals multipath will not show up as ghosts in it video image as it does with analog TV, but can in severe cases prevent DTV reception regardless of the strength of the TV signal. Multipath can best be addressed by use of a directional TV antenna. See the discussion below on the suggested types of antennas that can help reduce multipath.
Suggested Antenna Types/Location for DTV Reception &endash; The type of antenna you select for DTV reception may be limited by the available mounting location. In you live in an apartment or other location that necessitates the use of an indoor antenna located near your TV set then your options are limited. On the other hand if you live in a home or townhouse where outside antennas can be used then you have a more ideal situation. Most DTV broadcast stations are operating on UHF frequencies (see the list of TV stations). In the rare cases were DTV transmissions are occurring on VHF this may be interim situation with the goal of eventually having all DTV broadcasts on UHF still a long term possibility. Thus in most locations in the U.S. you do not need to be concerned about VHF reception for DTV (check the list of DTV stations above to determine if you location has local DTV stations on VHF). For this reason the following discussion is limited to UHF but many of the general ideas also apply to VHF. The use of UHF for DTV provides the maximum flexibility for antenna selection and location as UHF antennas tend to be quite small as compared to VHF antennas.
The most basic type of TV antenna is dipole. This is what you have with a simple set-top rabbit earsor UHF bow-tie antenna. These antennas have a signal pickup pattern that resembles the figure 8, where signals are received equally well from the front and the back of the antenna but poorly from the sides. Many of the relatively expensive antennas being sold for DTV are in reality nothing more than a simple dipole with the addition of a built-in amplifier. If you are serious about DTV reception I would advise you to avoid such antennas. Such antennas will, at best be marginally better than the very simple, inexpensive alternatives mentioned above. Moving up the scale in technical capabilities are antennas that provide additional gain in the forward direction and better rejection of signals arriving from the sides and back of the antenna. This provides two positive benefits. First it increases the received signal level from TV stations located toward the front of the antenna (i.e., the antenna has gain in the forward direction) and second it provides rejection of multipath signals and sources of electrical noise arriving from other directions. There are general approaches to designing a high gain UHF antenna. The first is place multiple bow tie elements, one above the other, with a wire grid reflector behind the bow tie elements. The second UHF antenna type is a 'yagi' antenna where the a number of short metal rods (i.e., the elements) are placed horizontally along the length and perpendicular to a pipe support pipe (i.e., the boom). A V-shaped reflector (i.e., corner reflector) is usually placed at the rear of a UHF yagi antenna. The third type of high gain UHF antenna is normally only found in commercial applications is a parabolic disk with pickup (i.e., the feed) placed at the focal point in front of the parabolic reflector dish. The dish is usually not a solid reflector as is typical for satellite dishes. Rather is made of a grid of small tubes or heavy wires.
In the UHF antenna configuration with stacked bow ties and a reflector , moderate gain is provided and superior rejection of multipath from nearby aircraft . Yagi antennas can provide moderate to high gain, but can become up to 10 feet in length for the very high gain versions (2 to 4 ft.for moderate gain versions). I feel the stacked bow-tie configuration is superior for most cases except for where the maximum possible gain is necessary to receive weak DTV signals, such as from a distant TV station. Also if your location suffers from severe multipath reflections from nearby structures then a high gain yagi may do a better job of rejecting this type of multipath.
Yagi and Stacked Bow Tie UHF TV antennas
If possible you should use an outdoor location for your antenna. Ideally it should be mounted at least 20 ft. above ground level and have a clear, unobstructed view in the direction of the TV stations' transmitter locations. Indoor, including attic mounting will normally provide at least a 50% reduction in signal strength as compared to outdoor mounting. Unless all of the DTV stations are located in the same direction from your location you will need an antenna rotator (motor and control unit) to be able to turn the antenna to the proper direction for best reception of each DTV station. Small changes in antenna vertical position can make a big difference in received signal strength. If your location is 'over the horizon' from the TV station's broadcast tower (i.e., antenna) then the received signal will probably have peaks and nulls spaced about 9-to-12 inches apart vertically. Therefore you should try moving the antenna mounting location up and/or down a few inches to find the vertical position that provides the best signal for the DTV station(s) for which reception is most difficult. The stacked bow tie antennas use a configuration that makes them less sensitive to small changes in vertical position.
The Consumer Electronics Association has a web site called AntennaWeb that can help you decide the class of outdoor antenna you will need to receive the TV stations (analog and digital) from your specific location. The major antenna manufacturers have gotten together to use a standard rating system for the reception ability of their antenna's (the antenna gain and directionality). Each antenna is assigned one of 7 color codes based on its performance. The above web site will recommend which rating (color code) you will need for your specific geographic area. The idea is that you match the color code on the antenna box with the color code for your geographic area. I would suggest you view this only as a guideline and for DTV reception go up at least one category and pay the extra few dollars to purchase a higher gain antenna. The following sequence of color codes are with the yellow code corresponding to the lowest performing antennas and thus appropriate to use geographic areas near the TV stations and at the other extreme the pink code being the a high gain, directional antenna suitable for use in difficult reception areas.
ANTENNA COLOR CODES: yellow - dark green - light green - red - blue - violet - pink
Signal Distribution - Once have have selected, located, oriented a TV antenna that provides a good quality signal at the antennas terminals then you will need to design your signal distribution system so as to not seriously degrade this signal. If you are located within a few miles of the TV stations transmitter and the distance between your TV antenna and your DTV receiver is modest (e.g., up to 100 feet) then you may be able to simply connect a good quality cable between the antennas terminals and the input to the TV receiver. You should always use a good quality coax (i.e., 75 ohm) cable for the signal distribution with RG-6 being the preferred type of cable. Most antennas have connection terminals intended for twin-lead (i.e., 300 ohm) cable. You will need to add a 300 to 75 ohm transformer right at the antenna and then connect the coax (i.e., 75 ohm) cable to the transformer. If you are more than a few miles from the DTV stations of interest then you may need to also add an signal amplifier (preferably right at or near the antenna). Many such amplifiers intended for use outside at the antenna will have the 300 to 75 ohm transformer built-in allowing for a short twin-lead (300 ohm) input connection from the antenna terminal and a coax cable output from the amplifier. For outside antenna installations you will also need to add a grounding block just before the antenna enters the dwelling. The grounding block requires that you run a heavy gage wire to a ground rod that is pounded into the ground or to another suitable earth ground. This is a precaution in the case of nearby lighting strike and is require by most local building codes. Once inside the house and if you have an outside mounted amplifier, you will need to run the coax cable to a power supply. From this power supply you run the coax either to a signal splitter (if you need to feed the signal to more than one DTV/TV receiver) or directly to the DTV receiver (if it is the only device using the antenna).
If you are looking for a web location to purchase your DTV antenna, amplifier or accessories, I can recommend Stark Electronics. They carry Channel Master and Winegard products and offer substantial discounts off of list prices.
Video Display Technologies
Article is courtesy DTVMAX.Com
Cathode Ray Tubes (CRTs) were virtually the only available television/video display technology for the first half century of television. Within the past decade however alternative technologies began appearing. Two of the new display technologies seem to hold the potential of displacing CRTs for conventional direct view displays and for projection displays.
Conventional CRT based direct view televisions were virtually the only choice the consumer had available until the mid-1970s. At that time Advent Corp. came out with the first high quality consumer projection television. The "Videobeam 1000" used three CRTs (i.e., red, blue & green) incorporating a unique Schmidt-Cassegrain optical design. The Advent projector was a 2-piece front projector in which a relatively large floor standing unit projected a 7 foot diagonal picture onto a curved, aluminized screen that was placed 8 foot in front of the projector. Other companies followed with their own projectors. Many of these were of a one piece design, but were still front projectors. The market for CRT based TVs has settled out into three basic categories today. First are the convention direct view TVs ranging in picture size up to 40 inches diagonal. Next are one-piece rear projection sets the span the picture sizes from 40 to 80 inches diagonal. Virtually all well known TV manufacturers now offer one-piece rear projection TVs. Finally, there are two-piece units that consist of a video projector and a separate screen. The screen can be either a front projection screen or a rear projection screen. Front projection configurations are far more common for home theater applications. A given projector can typically be used with various screen sizes ranging up to around 120" diagonal as the largest practical for most home theaters. Quality projectors of this third category currently represent the top end of the home theater display market. Some of these projectors allow switching between a 3 X 4 ratio and a 16 X 9 ratio picture. These projectors are often sold through industrial video dealers and dealers specializing in high-end home theater systems. Do not expect to find them at Circuit City or Best Buys. Sony, Runco, AmPro, and Zenith offer high quality two-piece projection systems spanning a broad price range.
Perhaps the best buy for a video projector for a home theater is a used Sony CRT projector. These are very high quality and could be found at truly bargin prices on the used market (at only 20% to 40% the cost of a new projector). The best models to consider are the VPH-1272 (uses 7" CRT and was manufactured from 1995 until 1997) and the VPH-G70Q (uses advanced design 8" CRTs and was manufactured from 1997 until 1999). A VPH-1272 will 2500 to 3000 hours of use will cost you $2000 to $2600 and the newer, brighter and higher resolution VPH-G70Q with 1000 to 2000 hours of use will cost $5000 to $7000. The nominal CRT life for Sony projectors is 10,000 hours therefore such used projectors will still have years of life remaining the CRTs. A recommended source for used Sony projectors is Extreme Projections.
Liquid Crystal Displays (LCDs) have become popular over the past decade for small hand held TV sets and as the displays on camcorders. At the other end of the display size, LCD based video projectors have become increasingly popular. From the beginning Sharp has been a leading manufacturer of such projectors. LCD projectors have improved with the current units having improved resolution and producing a brighter picture as compared to older units. LCD projectors offer the convenience of small size and light weight as compared to CRT projectors. However the image quality has generally been mediocre in comparison to a good CRT projector. LCD projectors' images have tended to appear course with obvious visible pixels when displayed on a large screen. This is due to the relatively small size of each pixel as compared to the relative large black area surrounding each pixel. However the latest, and most expensive (i.e., in the range of $6000 to $7000 retail price) LCD projectors from companies such as Telex (model P600 - $8995) and In Focus/Faroudja (model LS700 - $12,995) are very substantially improved in this area. Although improved from earlier generations of LCD projectors, the picture quality of the best LCD projectors is equivalent to that of a lower-end two-piece CRT projector or a relatively high-end one-piece projector. However the better LCD projectors do provide a relatively bright image. As for the best LCD projector, the Sony VPL-VW10HT (shown below) is arguably the best available for HDTV. Only the Sony uses a LCD panel with a 16X9 ratio (rather than the typical 3X4 ratio). The Sony's 1366 by 768 pixel LCD panels can fully resolve the 720P HDTV format while the 1080I HDTV format must be downconverted for display. All other LCD projectors using 3X4 LCD panels must limit vertical resolution when displaying widescreen 16X9 video since not all of the LCD panels vertical pixels can be used.
Plasma Displays was one of two new video display technologies that appeared in 1997 on the high-end consumer market. These are flat panel direct view units that will be produced by a number of Japanese manufacturers. Plasma displays are now available with a diagonal picture sizes up to 50 inches and a total cabinet depth of 2 to 4 inches. These TVs are the realization of a 40 year old prediction that large screen TVs would one day become available that you could hang on the wall. The retail price for large screen plasma displays is starting off high (i.e., in the $10,000 to $25,000 price range). Expect to see costs fall as production volume goes up, but if and when plasma TVs will become cheap enough to be considered mainstream is anyone's guess. While the latest models are substantially improved over the first generation products of two years ago, the qualify of the video displayed on a plasma display is still not up to the standards of either a high quality direct view CRT or a CRT based projector.
Digital Light Processor (DLP) was the second new consumer television display technology that appear in 1997. The basic DLP module is being produced by Texas Instruments (TI). DLP based projectors designed for displaying computer graphics went on sale in 1997 by several companies, with products aimed at the computer graphics presentation market. One of the first companies of offer DLP projectors was Vidikron with their Helios series. More recently a number of other companies have produced more affordable DLP projectors. The DLP projectors from Dream Vision has been labeled by a few publications as a best buy at a price of $6500. The Dream Vision uses a single DLP chip with 800 X 600 resolution. A very similar DLP projector is available from Davis (the 'CinemaOne') that is more frequently discounted at a lower price. Davis also offers higher resolution DLP projectors. InFocus is another major supplier of DLP projectors. These portable DLP projectors delivers a big, bright image. The heart of the DLP is a high intensity light source and a micro-mirror assembly (on a chip) in which each mirror corresponds to a pixel. Each mirror flips between two positions. In the 'ON' position the light is reflected toward the projection optics and in the 'OFF' position the light is reflected away from the projection optics. The intensity of a given pixel is determined by how long the corresponding mirror remains in the 'ON' position. Each mirror is square and there is very little black area between each mirror. High-end industrial DLP projectors will use three of the micro-mirror units (i.e., one each for red, blue and green). Lower-end units, including the initial consumer units, will use a single, or dual, micro-mirror unit(s) and a rotating color wheel to alternate between the red, blue and green components of the video image. DLP based projectors are available at prices starting in the $4000 range with the most expensive models using 3 of the DLP 1024 X 768 resolution micro-mirror chips and high intensity light sources cost as much as $50,000.. Projected images appear very smooth without the individual pixels being obvious. The initial DLP units had 800 by 600 pixels. DLP projectors were initially being sold for projecting computer graphics where the 800 X 600 pixels correspond to SVGA resolution. XVGA resolution (1024 X 768) DLP projectors are now also available. TI has demonstrated in 1999 a high-end commercial DLP projector designed for the high definition TV standard, but consumer HDTV DLP projectors capable of displaying 1920 by 1080 pixels are still some time away. However, this could turn out to be the technology that eventually replaces CRTs for video projectors. Only time will tell. TI is also demonstrating DLP based commercial projectors for movie theaters. There is a big push by a number of Hollywood studios in this direction and you can expect to see DLP electronic cinema projectors to start showing up in your local multiplex within the next two or three years. As for consumer DLP projectors for 2000, several manufacturers including Mitsubishi, Panasonic and Hitachi will be introducing in late 2000 rear projectors that will use a new 16X9 DLP chip that provides 1280 X 720 pixels. These projectors will fully support the resolution of the 720P HDTV format. You can also expect to see the current manufactures of DLP front projectors, such as Dreamvision, to incorporate this new DLP chip in their future products.
Direct-Drive Image Light Amplifier (D-ILA) is an technology developed by Hughes and JVC. All sales of D-ILA projectors are handled by commercial division of JVC and a few other companies licensed by JVC. D-ILA projectors use reflective LCDs (on CMOS chips), rather than the transmissive LCD used on conventional LCD projectors. The result is a technology similar to DLP in several ways. D-ILA projector prices start at about $15,000 and go up from there. Currently higher resolutions are available in D-ILA projectors than in DLP or conventional DLP projectors. The overall quality of the project image with D-ILA is quite good and very bright. The most expensive D-ILA projectors are suitable for use with very large screens. The JVC model ILA-12K has a sensational 10,000 lumens (compared to 600 to 800 typical for a CRT, LCD or consumer DLP projector) of brightness along with a better-than-HDTV resolution of 2000 by 1280 pixels. This projector can be used with screens up to 60 feet. At the other end of the price and performance scale the JVC models DLA-G10U and DLA-S10U offer 1000 lumens of brightness and a resolution of 1365 by 1024 pixels. These models support both 3 by 4 and 16 by 9 displays and are compatible with DTV/HDTV standards. These latter models may be of more interest to consumers for home theater use. JVC is expected to induce its first consumer rear projector during 2000 based on the D-ILA technology (a 61 inch model). JVC will also be releasing in August 2000 a new front projector (model DLA-G3010Z - $9000) that uses a 1365 x 1024 pixel D-ILA panels for HDTV.
Video Display Installation and Setup
Article is courtesy DTVMAX.Com
One important consideration when purchasing a new TV set/monitor (either direct view or a projector) or when setting up a home theater is achieving the proper alignment of the TV. Manufactures generally ship their TV sets in a state of gross misadjustment. I'm not just taking about the proper setting for the user controls (e.g., brightness, contrast, color, hue, sharpness), but also about the set's internal controls. The manufactures believe that most consumers don't really care much about the picture quality. The vast majority of consumer TV sets have the overall picture intensity set far to high (i.e., well outside of the TV set's linear range) resulting in picture blooming (gross loss of details) in the brightest areas in the picture. These manufactures believe the consumer when confronted with a 'wall of TVs' at the local electronics superstore will pick the one with the brightest picture, even if the picture is poor in many other aspects. The color accuracy is generally poor with the overall color balance shifted toward the blue end of the spectrum (i.e., color temperature too high). Also the color balance generally will not track well between bright and dark objects or scenes (poor gray scale). A properly trained technician equipped with the needed test tools can adjust most TV sets to vastly improve upon the out-of-the box picture quality. The Imaging Science Foundation (ISF) was established by Joel Silver and Joe Cane to provide the training for technicians and to educate consumer and dealers on the benefits of proper calibration of TV sets/monitors. ISF sells a test disk called 'Video Essentials', available on both Laserdisc and DVD, that can be used by either the technically knowledgeable consumer or by a technician to calibrate a TV set. Generally the consumer will be limited to only adjusting the readily assessable user controls. When purchasing a quality TV set for your home theater, I suggest you seek out a dealer that has been trained by ISF (check out the ISF web site for dealer information) to calibrate you TV. If you are looking for more information on this topic I strongly recommend you purchase a publication from Widescreen Review magazine called "Imaging Science Theater 2000". This back issue is packed full with many technical and semi-technical articles on the proper setup of TV sets/monitors, the selection of the proper type of projection screen and the proper environment for your home theater. This issue was released in February 1998. You can try contacting Widescreen Review Magazine to order this back issue.
If you are installing a front projection system, you will need both the video projector and a projection screen. The two leading manufacturers of projection screens are Stewart Filmscreen and Da-lite. Da-lite also manufactures rear-projection screens than can be used to substantially enhance the performance of an already good quality rear projection TV set.
Video Line Multipliers
Article is courtesy DTVMAX.Com
Video line multipliers are devices that accept an input of a video signal and through digital processing artificially increase the number of scanning lines and/or convert the video from an interlaced image to a progressive scanned image. The primary goal of a video line multiplier is to reduce the visibility of the horizontal scanning lines. These devices can only be used with data and graphics grade monitors/projectors capable to supporting high resolution and high horizontal scanning rates. Until recently all such devices were called video line doublers because they exactly doubled the number of horizontal scanning lines in a given unit of time. In this process they also doubled the horizontal scanning frequency from the standard 15.75 KHz to 31.5 KHz. Within the past couple of years line triplier and line quaduplers have also appeared. Also Dwin introduced a multiplier that featured variable multiplier values (i.e., called video scaling) to allow the user to select the optimum value (e.g., 1.6) for their specific monitor/projector. Several other manfacturersd have followed Dwin's lead and also introduced video scalers. Also up until recently all line multiplers that produced quality results were quite expensive. Recently an affordable video line doubler has been introduced by DVDO that at $695 represents a real bargain. The better quality line multipliers include a feature called 3:2 pull down for the better conversion of film based material (i.e., movies) filmed at 24 frames per second to progressive can video at 60 frames per second. DVDO was the first manufacture to offer this feature on a low cost line multiplier and more recently Focus has introduced a relatively low cost unit (but still 3 times the price of the DVDO unit) that includes 3:2 pull down. If you have a high quality data or graphics grade video projector that has component and/or RGB inputs then a line multiplier can make a real improvement when displaying conventional standard definition analog or digital video sources. Virtually all HDTV sets or set top receiver boxes have a built-in line multiplier for upconverting analog and standard definition digital video to the same number of scanning lines as used for HDTV (i.e., 1080I). However this built-in multiplier is frequently of mediocre quality and do not support the 3:2 pull down enhancement.
Article is courtesy DTVMAX.Com
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