Updated - January2009

 

In the final days of 1996, the Federal Communications Commission (FCC) approved the digital television broadcast standards for the United States. All DTV broadcasts will be on UHF channels 14 to 51 and on VHF channels and the current higher numbered UHF channels are being auctioned off by the Government for non-TV use. Although the official phase-out date for analog broadcast TV in the U.S. as initially set by the FCC and US Congress as the end of 2006, the phase-out of analog TV in the US was delayed until Feb. 17, 2009.  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 modes that had been defined by the Grand Alliance's Advanced Television System Committee (ATSC). The highest resolution mode proposed is 1920 X 1080 pixels. Currently there are only two HD formats actually being used for US broadcasts.  NBC, CBS, and CW are using the 1080i format for their HD broadcasts (as are most HD cable/satellite distributed channels).  This mode uses 'interlaced' scanning, as does traditional analog TV. With interlaced scanning the odd numbered scanning lines (i.e., lines 1, 3, 5, etc) are transmitted in the first 1/60 second and the remaining even numbered lines are transmitted in the next 1/60 second. By combining these two 'fields' one complete frame of the video is transmitted every 1/30 second. This is referred to as 1080i/60.  A 720p HD format is being used by ABC and Fox along with a few HD cable/satellite channels such as ESPN.  With 720 line progressive, or non-interlaced, mode the 720 scanning lines are displayed sequentially (i.e., 1, 2, 3, 4, 5, etc.) each 1/60 second. 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 is originally recorded in progressive 60 Hz mode). This HD format is referred to as 720p/60.  The letter "i" or "p" will normally 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 (currently used for film sources from Blu-ray Disc and some pay-per-view movies offered by Dish Network and Directv, but over-the-air broadcast TV stations), 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 and/or convert the resolution to a different value for display. For example most recent vintage HDTVs that have a display with a true 1080p display (i.e., 1080 x 1920 pixels and displayed in a progressive mode) will convert all video inputs to 1080p/60 or for some higher-end newer models 1080p/120 or even 1080p/240 for display.

The digital broadcast TV standards in the US allow modes for standard definition TV (i.e., SDTV - 480i mode), with about twice the horizontal resolution of conventional analog broadcasts (similar to that provided by DVD or Directv), as well as enhanced definition TV (EDTV - essentially the same resolution as SDTV but with progressive scan rather than interlaced and a widescreen format) 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 EDTV and HDTV 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 up to 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., 480i). Dolby Digital encoded audio is the same as currently used on DVDs and some satellite channels. 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.   It is the high definition modes that are of most interest to quality conscious home theater owners. However, any television set claimed to  be a "High Definition Digital Television" must support reception of all 18 modes AND should display images at either or both the 720p and the 1080i modes.. Note that some projectors/monitors that can only support display of resolutions up to 720P must downconvert 1080i video to 720p for display. Other less sophisticated DTV sets may be sold that may receive all 18 DTV broadcast modes but will down-convert the high definition modes for display at lower non-HDTV resolution (typically 480p EDTV mode). To confuse matters even further most sets that are allowed to be called HDTV capable are not actually able to display the full 1920 pixels in the horizontal direction as long as they can display the required vertical resolutions.  For example some plasma flat panel displays in sizes of 42 inch only display 768 x 1024 pixels, instead for the full 720 resolution of 720 x 1280 pixels, yet they can advertise such DTVs and 720p HDTVs..  Both flat panel HDTV as well as digital projectors using 1080 x 1920 pixel displays are now widely available and the price difference from lesser 720p HDTVs has now decreased significantly.  Generally the term FULL HD is used to indicate that the HDTV will display the full 1080p resolutions. 

In August 2000 the Consumer Electronics Association (CEA), an industry group whose membership includes most of the DTV manufactures, agreed on new uniform names for DTV products in a attempt to end the confusion.   The following summarizes the CEA agreed upon name for digital television (DTV) sets and monitors:

 

DTV Product Name	DTV broadcast reception capability	DTV display ratio and min. display mode	DTV min. display  resolution	Audio output capability
High Definition Television (HDTV)	all 18 ATSC DTV modes	16X9:  720p and/or 1080i	at least 540p (for 720p broadcasts) and at least 810i (for 1080i broadcasts)	Dolby Digital
High Definition Television Monitor (HDTV-Monitor)	none (must use an external DTV receiver box)	16X9:  720p and/or 1080i	at least 540p/at least 810i (for 720p and 1080i reception)	none
Enhanced Definition Television (EDTV)	all 18 ATSC DTV modes	3X4 or 16X9: 480p	at least 480p	Dolby Digital
Enhanced Definition Monitor (EDTV-Monitor)	none (must use an external DTV receiver box)	3X4 or 16X9: 480p	at least 480p	none
Standard Definition Television (SDTV)	all 18 ATSC modes	3X4 or 16X9: less than 480p (e.g., 480i)	less than 480p (e.g., 480i)	usable audio required

DTV Televisions, Monitors & Projectors

As to 2009 HDTVs fall into the following categories and technologies:

Flat Panel HDTVs: 

Plasma - Generally available from many major manufacturers in screen sizes of 42 inches to 65 inches.

The Good - Better sets have excellent contrast with deep blacks; very wide viewing angles without loss of image quality

The Bad - Many, but not all,  models don't offer anti-reflecting screens; more power consumption than LCD HDTV, some older models had a potential for image burn-in (but not an issue with most current plasam HDTVs); generally are heavier than similar size LCD models.

LCD - Generally available from many manufacturers in screen sizes for less than 20 inches up to 65 inches.

The Good - The very best LCD HDTVs (generally with LED back lighting and zone dimming) have very good contrast and deep blacks; less power consumption that plasmas HDTVs.

The Bad - Most models have a limited viewing angle with image contrast and brightness degradation as the viewer moves off axis;  many models have poor black levels and mediocre contrast.   

Rear Projection TVs - RPTVs are losing market share to flat panel HDTVs, but still offer the best performance to price ratio for large screens sizes (60 inches or more).  Most remaining rear projector TVs (RPTV) use DLP technology.

The Good - The best RPTVs produce excellent images with excellent contrast and deep blacks;  In screen sizes larger than 60 inches RPTVs can be significantly less expensive than such large screen plasma and LCD flat panel HDTVs (but the gap is closing).

The Bad - RPTVs have a limited viewing angle with image contrast and brightness degradation as the viewer moves off axis; low cost models use a bulb that must be replaced typically every 3,000 to 6,000 hours at a cost of $200 to $400 (however many newer models use LED or laser based light engines that last 20,000 or more);  RPTVs have cabinets that are bulkier for flat panel HDTV and generally are not practical for wall mounting.   

Front Projection TVs - FPTVs are the preferred technology for home theaters with really large screen sizes (i.e, 80 inches or more).  FPTV are used in combination with a projection screen and FPTVs can accommodate a range of screen sizes.  The light output of the projector, distance between the projector and screen, the size and gain of the screen, as well as the viewing environment will determine the optimum screen size.

The Good - The better FPTVs produce excellent images with excellent contrast and deep blacks and full 1080p resolution;  In screen sizes larger of 80 inches or more (e.g., 100, 120, 135 inches) RPTV are essentially the only practical alternative;  the only real alternative for a true movie theater experience in your home..

The Bad - RPTVs require room light control  to produce an good or excellent image.  While movie theater dark conditions are not absolutely necessary, being able eliminate light sources and painting the ceiling and walls a dark color help improve image quality;  Mounting of FPTVs can be more difficult since frequently a ceiling mount is the best solution, but requires custom electical and signal wiring work.  

 

   DTV Video Interfaces

Two 'families' of HDTV compatible interfaces are used for HDTV consumer produces.  Up until late 2001 all consumer DTV/HDTV products provided only analog interfaces.  By 2004 most new DTV products included one ore more digital interface, generally in addition to analog interfaces.  Today virtually all curent HDTV models have 1 to 4 digital HDMI (High Definition Media Interface) inputs as well as 1 or more types of analog inputs. 

ANALOG INTERFACES:  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 video processor 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., video processor 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 with PCs 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 (a 15-pin connector used for PCs and PC monitors) 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.  In the early days of  HDTV, a few manufactures ( e.g., RCA, Mitsubishi, Sharp, etc.) 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 and some current HDTV models still include a VGA style connector to allow for the connecting to a PC.

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).  These 3 connectors are typically color coded red, blue and green.  Toshiba introduced component video to the consumer video world with their first generation DVD players and a projection TV set using a standard definition component interface.  While this original version introduced by Toshiba for their DVD players and TVs is not compatible with HDTV standards, most HDTV manufactures now include on their HDTVs a least one component video interface that is an enhanced version, suitable for HDTV.  The HD version is technically called and sometimes labeled Y Pb Pr (or Y Pr Pb).

  

Component Video Cable

Most HDTVs also include at least one, and sometimes two, types of standard definition video inputs.  The oldest type, and also the lowest quality, is a composite video input that uses a single phono connected that is usually color coded yellow.   The second type of standard definition input found on some HDTVs is a 'S-Video' input.  This uses a single 4-pin round connector.  The S-Video interface offers improved performance as compared to a composite video connection but neither composite video nor S-Video support high definition video.

                                            

Composite Video w/Stereo Audio Cable                                                    S-Video Cable

Note that all types of analog video interfaces described above require a separate audio connection.  For two channel, stereo, audio this is typically carried via a cable paires with 2 phono (e.g, RCA)  plugs on each end that are color coded either red and white -or- red and black with the red cable/connector being for the right audio channel in either case.  For surround sound (e.g., Dolby Digital or DTS) an optical fiber cable, called Toslink, is the most common connection, but some devices use a coax cable with phono connectors on each end to carry the digital audio signal.

 

DIGITAL INTERFACES:  

 

DVI/HDCP and HDMI   As if the multiple incompatible types of analog interfaces weren't confusing enough to the less technically inclined consumer, multiple types of digital interfaces have been used for consumer DTV products.  During 2002 DirecTV, Dish Network, a number of consumer electronics manufacturers and several movie studios combined forces to back the introduction of a high speed Digital Visual Interface (DVI) along with high-bandwidth digital content protection (HDCP) on their HDTV products.  This new interface provided the means for movie studios to control the distribution of high definition programming and will provide the means to prevent HD copies from being made.  Many DVI/HDCP enabled HDTV monitors and projectors were offered as were HD receivers from DirecTV and Dish Network.  Some cable HD set-to-boxes (STBs) became available in 2004 that included a DVI/HDCP interface to connect to HDTV monitors/projectors and all cable companies were required by federal regulation to offer HD-STBs that include DVI/HDCP outputs by mid-2005 (lated updated to allow HDMI instead). For now the earlier generation of HDTV monitors/projectors that only supported analog HDTV video inputs are still supported since the satellite and cable STBs also include component video outputs.  However, DVD and Blu-ray Disc players are now available that are capable of providing their highest output resolutions via a digital interface with copy protection while the component video output has resolution constraints imposed by the DVD and Blu-ray Disc license bodies.  A newer variation of DVI/HDCP is called HDMI (High Definition Media Interface).  This extension includes support for the video interface features of DVI and also adds support for the transfer of audio, including support for various surround sound formats, up to 7.1 channel lossless audio formats from Dolby and DTS.  The initial products with HDMI inputs or outputs were released during 2004 and starting in 2005  HDMI generally replaced DVI on new consumer HDTV products.  HDMI is backward compatible with DVI/HDCP interfaces but since it uses a different type of connector, a special DVI to HDMI adapter cable is required to interconnect DVI with HDMI devices.  In this case a separate audio cable is also required (since DVI does not support the transfer of audio).  Effective July 2005 all U.S. cable TV companies that offer HD services were required at the customer's request to provide a set-top-box (STB) that includes a active DVI or HDMI output.  Also note that DVI and HDMI are only applicable to the interface between a HDTV source device (e.g., HD satellite receiver, HD cable box or Blu-ray Disc player) and the HD display and it is not suitable for connecting a HDTV source to a HD recording device, such as a future generation of high definition Blu-ray Disc recorders.  

                    

            DVI Connector                                     HDMI Connector

 

IEEE-1394    A second type of digital interface found on some HDTV equipment is based on the IEEE-1394 standard and combined with a content protection scheme (called DTCP or 5C) is the second overall category of digital interface used for HDTV.   The IEEE-1394 interface currently goes under various trade names such as iLink, and Firewire but the addition of the DTCP content protection provisions are necessary in DTV/HDTV consumer products.  In November 2001 the Consumer Electronics Association (CEA is an associated whose members are the major consumer electronics manufactures) announced plans for an industry-wide name "DTVLink" and a logo to be used with future digital television products (including monitors/projectors, digital VCRs, cable TV boxes, HDTV set top receiver boxes, etc.) that support an IEEE-1394 digital interface combined with DTCP anti-piracy protection provisions.  However many manufacturers have not yet adopted this CEA recommendation and as a result naming variations still exist between the various manufacturers.  While the main role for the DVI and HDMI interfaces described above is between a HD video sources (e.g., cable STB) and a HD television, monitor or projector, the role for the IEEE-1394 interface is primarily between a HD video source and a HD recorder (e.g., the now discontinued D-VHS format and future Blu-ray Disc recorders).  There were a few manufacturers (especially Mitsubishi and JVC) that have been including IEEE-1394 inputs on their HD monitors and projectors but the industry moved  to HDMI instead for this purpose.  Effective April 1, 2004 all U.S. cable companies offering HDTV channels were required by federal regulation to offer their customers STBs with an active IEEE-1394 port (with DTCP).  Satellite providers DirecTV and Dish Network have not, nor have shown any intensions of supports IEEE-1394 outputs from their HD receivers and digital video recorder (DVRs).

DTV Set Top Receiver Boxes

 

LG Electronics LST-3410 HDTV Receiver/PVR

 

Early in the roll out of HDTV a number of manufacturers sold HD set top boxes (STB) that were over the air receivers for HD broadcasts that were used with HD monitors (i.e., that lacked buitin HD tuners).  While a few HD monitors may still be found, just about all flat panel HDTV and rear projector HDTV include built-in broadcast HD tuners and a resuts the standalone HD STB have generally been discontinued.  However, some Directv and Dish Network DVRs offer either built-in or optional add-on HD broadcast tuners  Most of the DTV tuners sold to support the digital TV transition while capable of receiving both the standard definition and high definitional digital broadcasts, only output the received video in standard definition.   

Currently Directv offers the add-on model AM21 digital broadcast over-the-air tuner that is for use with their HR21, HR22 and HR23 HD-DVRs while the older HR20 had the over-the-air receiver built-in.  Dish Network offers the VIP622 and VIP722 that has inputs an antenna connector for over-the-air digital TV reception.

The following table lists now discontinued HD-STBs and HD-DVRs that support over-the-air reception of digital TV including HD.  You may still find some of these models on the used market and perhaps some new units are still available from some sources.

Manufacturer/Model (now Discontinued)	HDTV Interface Type(s)	Original List Price
DirecTV TIVO (includes HD-DirecTV receiver, TIVO HD-DVR, over-the-air tuner for only digital channels	Component/DVI	$999
DirecTV H10 (includes HD-DirecTV+ and over the air tuner)	HDMI/Component	$299
Hughes HTL-HD (includes HD-DirecTV+ and over the air tuner - manufactured by LG)	Component/RGB/DVI	$499
LG LSS-3200A  (includes HD-DirecTV receiver and over the air tuner - RF remote control)	Component/RGB/DVI	$699
Samsung SIR-TS360 (includes HD-DirecTV receiver and over the air tuner)	Component/RGB/DVI	$599
RCA DTC-210 (includes HD-DirecTV receiver and over the air tuner)	Component/RGB/DVI	$599
Dish PVR 921 (includes Dish Network HD receiver with HD-PVR and over the air tuner) Also sold as JVC TU-DVR921RU	Component/DVI	$549
Dish PVR 942 (mid-2005 - includes Dish Network HD receiver with HD-PVR and over the air tuner) Replaces model PVR 921	Component/DVI	$699
Dish 811 (includes Dish Network HD receiver and over the air tuner)	Component/DVI	$399
JVC TU6000RU (includes Dish Network HD receiver and over the air tuner module)	Component	$649
RCA HD 6000 (includes Dish Network HD receiver - no over the air tuner)	Component	$499
HUMAX HFA100 (over the air tuner)	HDMI/Component/RGB (VGA)	$249
LG LST-4200A (includes over the air and digital cable tuner for 'clear channels)	Component/RGB/DVI	$349
LG LST-3410A (includes over the air and digital cable tuner for 'clear channels' and PVR) previously sold as Zenith HDR-330	Component/RGB/DVI	$999
LG LST-3510A (includes over the air and digital cable tuner for 'clear channels' ) previously sold as Zenith HDX-230	Component//RGBDVI	$699
Mitsubishi HD5000 (over the air and digital cable tuner)	DVI/IEEE-1394	$1699
Panasonic TU-SDT52 (only digital over the air)	Component	$399
RCA ATSC21 (over the air tuner)	Component/RGB/DVI	$499
RCA ATSC11 (only digital over the air tuner)	Component/RGB/DVI	$449
Samsung SIR-T451 (over the air and digital cable tuner	Component/DVI	$499
Samsung SIR-T151 (over the air tuner)	Component/DVI	$499
Samsung SIR-T165 (over the air tuner)	Component/DVI/IEEE-1394	$669

DTV Programming

 

CBS,  NBC, ABC and/or FOX began DTV broadcasts in a few U.S. cities in late 1998 and by 2004 there was at lease some digital broadcast stations servicing all market areas within the U.S.  CBS, NBC, CW & PBS are supporting the 1080i (1920 X 1080 interlaced) HDTV format while ABC and Fox are supporting the 720p (1280 X 720 progressive) HDTV format.   A summary of the network schedules, include HDTV programming can be found here..  

Cable TV - Most of the major cable companies, such as Time Warner, Comcast and Cox, are now offering some HDTV channels.  Typically these cable companies are offering the major local network broadcast HDTV stations, plus several HD premium offerings from HBO, Showtime, Starz, and the HD versions of popular cable channels such as CNN, ESPN, A&E, Discovery, etc.

Directv is offering 130+ HD channels but of these perhaps 1/2 are associated with sports programming packages, pay-per-view offerings and the premium movie channels such as  HD-HBO, Showtime-HD.  Directv currently has the major network local stations (typically at least ABC, CBS, NBC, and Fox) available in HD in many parts of the country and they will be available for most remaining US locations by the end of 2009.  Directv also has national HD feeds for NBC, CBS, ABC and Fox but only those customers that cannot receive the local channels, even if just in standard definition, via Directv or over-the-air qualify to receive these channels.  

Dish Network also offers several levels of  HDTV programming packages under the name Zoom HD.  Prices start at $24.99 per month for the least expensive Zoom HD package .

Click Here for the HBO Monthly Programming Guide (including HD-HBO)

Click Here for Showtime Program Schedule (including Showtime HDTV)

Click Here for HDNet and HDNet Movies Program Schedules

Click Here for the Discovery HD Schedule

Click Here for ESPN HD Schedule

 

National availability of HDTV programming is now a reality, not just in the cities where over-the-air HDTV stations are operational.   The HDTV DirecTV, Dish Network and Voom services are available nationally.  For DirecTV and Dish Network, the HD channels are being provided via new satellites located in different orbital slots from the previously used satellites. This means that to receive these HDTV DirecTV channels you will need a not only a new DirecTV receiver but also new DirecTV or Dish Network satellite dish. In some locations this new dish is also required to receive the local TV channels (via at the satellite service).  

DTV Broadcast Stations

All full power broadcast TV now have digital TV broadcasts.   Not all stations broadcast in HDTV, but certainly the affiliates of the major networks in all but a very few cases were broadcasting network HD programs in HD by the beginning of 2009.   An increasing number of local broadcasters have added local news programs in HD.

DTV Antennas

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:

• adequate signal strength

• adequate signal to noise ratio

• freedom from multipath

Achieving adequate Signal Strength – 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 station’s transmissions, and the geography/obstructions between your location and the TV station’s 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 – 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 – 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 station’s 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 – 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 currently (early 2009) operating on UHF frequencies, but after the digital transition is completed in 2009 some of these stations will be moving to VHF, thus requiring antennas that support both VHF and UHF reception.

The most basic type of TV antenna is dipole. This is what you have with a simple set-top VHF ‘rabbit ears’or 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 antenna.  The first alternative only applies to UHF antennas and it is to place multiple bow tie elements, one above the other, with a wire grid reflector behind the bow tie elements.  The second alternative is applicable to both VHF and UHF antennas and this type is a 'yagi' antenna where a number of  metal rods (i.e., the elements) are placed horizontally along the length and perpendicular to a 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.  For VHF yagi antennas generally the greater number of elements and the longer the overall length the greater the gain and the more directional the antenna reception pattern.

  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 UHF signal strength but such small changes in vertical position are typically less critical for VHF reception.  If your location is 'over the horizon' from the TV station's broadcast tower (i.e., antenna) then the received UHF signal will probably have peaks and nulls spaced about 9-to-12 inches apart vertically.   Therefore you should try moving the UHF 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 UHF antennas use a configuration that makes them less sensitive to small changes in vertical position.

The "Siliver Sensor" antenna, has been distributed under both the  Zenith (model ZHDTV1) and Philips (model PHDTV1) brands, is generally considered the best of the currently available indoor antennas for UHF reception.  However, it doesn't receive VHF and after the 2009 digital TV transition is complete an increasing number of DTV stations will be moving back to VHF. Terk makes an indoor antenna that combines a UHF section that seems to be copied from the Silver Sensor with simple 'rabbit ears'  for VHF reception.  Both an amplified version (model HDTVa) and a non-amplified version (model HDTVi) are available.  If your location is relatively near to the broadcast stations' transmission towers, such a simple indoor antenna may be all that you need.  If mounting the antenna in your attic is feasible, then a higher performance outdoor style antenna can generally be used and will usually provide for a better signal strength that using simple indoor style antennas..

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 very 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 antenna’s 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 antenna’s 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 antenna’s 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, offer substantial discounts off of list prices and excellent customer service.

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Video Projectors

Cathode Ray Tubes (CRTs) were virtually the only available television/video display technology for the first half century of television. Video front projectors using 3 CRTs, one each red, blue and green, were the dominate technology for large screen home theaters from the mid-1970s through the 1990s.  However, within the past few years alternative technologies using digital micro-display technologies have appeared and as their performance improved and their prices dropped the CRT market share dropped slowly at first but by 2007 CRT projectors had virtually vanished from the consumer marketplace.

Liquid Crystal Display (LCD) Projectors use 3 small (typically under 1 inch) display panels with one each for the red, blue and green primary colors.  LCD based projectors were initially the lowest quality of the widely available digital display technologies with poor contrast and an inability to display deep blacks.  However recently a new generation of LCD display chips, with those manufactured by Epson, have vastly improved the performance of the best LCD front projectors.  1080p resolution models are now available from Epson, Panasonic and Mitsubishi that all use LCD display chips supplied by Epson and offer a high level of performance at a reasonable cost  (as compared to home theater oriented 1080p front projectors).

Liquid Crystal on Silicon (LCoS) Projectors  in an improved LCD technology that at its best can offer improved images as compared to conventional LCDs but at a somewhat higher price.  LCoS displays typically have a smaller space between individual pixels resulting in less of a 'screen door' effect in the displayed image.  LCOS image quality, in terms their native contrast ratio and its ability to display true blacks, come closest to matching the performance of the best CRT front projectors. JVC makes the best performing LCoS display chips and use these in their home cinema 1080p projectors.  JVC;s trade name for their LCoS technoloy id D-ILA.  Sony is the other current manufacture of LCoS front projectors, and their LCoS display chips result in a performance level, in terms of contrast ratio and black level, that is one tier below the JVC products and are more similar to the best LCD based projectors.

Digital Light Processor (DLP) Projectors  first appeared as a consumer television display technology 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.   However the DLP eventually found it way into home theater projectors and is now available from a number of manufacturers in both 720p and 1080p models.

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 and very high end consumer DLP projectors will use three of the micro-mirror units (i.e., one each for red, blue and green). Three chip DLP projectors are now becoming wide used in commercial movie theaters under the general category of digital cinema.  Consumer and business units, use a single mico mirror device (MMD) and a rotating color wheel to alternate between at least red, blue and green components of the video image. Home cinema DLP based projectors are available from many manufacturers, including BeaQ, Optoma, Marantz and many others, at prices starting in the under $1000 range for 720p models and starting in the $2000-$3000 price range for 1080p models.  The high-end models using 3 of the 1080p MMDs and high intensity light sources carry prices starting at around $15,000. 

Video Projection Screens

.If you are installing a front projection system, you will need both the video projector and a projection screen. Three popular US manufacturers of projection screens are Stewart Filmscreen, Vutec 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.  Within the past few years there are quite of number of US distributors importing screens from Chinese manufactures and selling these under various brand names.  Of these Elite Screens is one of the most popular and Saaria screens of widely sold on eBay..

 

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