TV antennas is one of the few technologies that has remained relatively unchanged - until now.
For 70 years the conventional wisdom was that manufacturers know all there is to know about antenna physics - and that there are no new ways to make antennas more powerful, efficient or compact.
That idea was challenged in 2003 when Antennas Direct set about creating the most powerful antennas on the planet.
Using sophisticated antenna simulation software, analyzers and test equipment usually reserved for military applications; Antennas Direct is creating antenna designs that are 2 - 10 times more powerful than the models currently sold in big box retail outlets. Some of these models have been unchanged for the last 50 years.
While major manufacturers continue to focus their attention into areas they feel have more promise, antennas have been left to wither on the vine. Their belief is that by 2009 people will no longer receive television signals with something as antiquated as an antenna.
On the way to the trash heap, two very important things happened. First, the nation's television broadcasters invested tens of billions of dollars in new HDTV transmitters, bringing perfect over-the-air HDTV to tens of millions of Americans without the need for cable. Plus, in most cases the image resolution was many times better than satellite or cable. Second, supercomputers developed by the military and computer-aided antenna design software became available to manufacturers. These tools offer the ability to create, simulate and test thousands of different antenna geometries in the time it would take to create a single antenna previously.
Today anybody with an HDTV and an HD tuner can capture these crystal clear signals from their local affiliates. This uncompressed signal offers the consumer the ability to take full advantage of high definition imagery unlike the HD offered by satellite and cable providers. This advantage is only one reason why the best HD can't be had through these providers. Over-the-air HD signals are also free. So, while the satellite and cable providers go into contract negations to decide which local affiliates are available to you and how much more to charge you for an inferior signal, you can enjoy pure HDTV free of charge.
HOW FREE SIGNAL TVWORKS
How Television Broadcasting Works While millions of people watch television each day, many of them are not quite sure how the technology works. Television has been around for many decades and although some of its components have changed over the years, the way in which television broadcasts work is pretty much the same.
Elements of Broadcast Television There are a several major parts that are required in order to receive television broadcasts. They include an image source, a sound source, a transmitter, a receiver, a display device, and a sound device.
Image Source The image source can be defined as the program. It can be a movie, TV show, news program, etc. The image source is just the source’s video and does not include the sound. The image source is usually recorded on camera or flying spot scanner.
Sound Source Once the image source is obtained, for e.g. a video of a movie, sound is needed to complete the medium. The sound source is the TV program’s audio signal, whether coming from a movie, TV show, news program, etc. It can come in the form of mono, stereo, or even digitally processed Surround sound.
Transmitter A transmitter is what sends both audio and video signals over the air waves. Transmitters usually transmit more than one signal (TV channel) at a time. A transmitter modulates both picture and sound into one signal then sends this transmission over a wide range for a receiver (TV set) to receive.
Receiver A receiver (TV set) receives the transmitted signals (TV programs) and turns radio waves, which include audio and video signals, into useful signals that can be processed into an image and sound.
Display Device This is either a TV set or monitor. A display device has the technology to turn the electrical signals received into visible light. On a standard TV set, this includes the CRT (Cathode Ray Tube) technology.
Sound Device The sound devices are usually speakers that are either built into the TV set or that accompany the TV set and turn electrical signals into sound waves to play audio along with the video images.
Broadcast Television Signals Broadcast Television Signals are video and sound signals that are transmitted over the air. Anyone using a television set that has a receiver and an antenna can pick them up for free. Antennas are used to grab as much signal as possible and to sometimes amplify the signal.
All TV sets have the ability to switch the receiver’s tuner to pick up specific channels. Each channel is transmitted on its own frequency, which the TV set can tune into and receive.
Broadcast TV vs. Satellite TV and Cable TV There are three main ways to receive TV programming, one is through broadcast television and the other two are through satellite and cable TV.
Broadcast TV Broadcast TV is when audio and video signals are transmitted over the air waves from a ground based transmitter. These signals are usually picked up for free and are on specific frequency spectra.
Satellite TV Satellite TV is usually a digital signal that is broadcast from a satellite orbiting the earth. They are usually pay services that require special equipment to receive programming and operate on special frequencies.
Cable TV Cable TV is a pay TV service that sends out signals not over the air, but through cable that runs from the cable company to the viewer’s home. Many cable types, from copper to fiber optic cables, are used. The signal can be analog or digital.
Television Transmission Bands Television is transmitted on various bands or frequencies. Transmission bands vary by country. In America, bands III to V are used, which include VHF and UHF signals.
Band I It is important to note that lower band signals such as bands I do not have enough bandwidth, which means they cannot carry much information.
Band II Band II in America is what carries FM radio. While this band is able to carry an audio signal, adding video to the signal would overcrowd it and it would be inferior to the signal that viewers receive today.
Bands III , IV, and V A Normal TV signal is located on Band III, IV, or V. Usually, these bands require bandwidth to carry both audio and video signals. Most TV signals have about 4MHz of bandwidth for the video portion, when the signal’s sound portion is added the signal will have a total of about 6 MHz. The FCC has allocated each TV channel to a bandwidth of 6 MHz. The channels are as followed:
Band III – Channels 2 to 6 (54 to 88 MHz)
Band IV – Channels 7 to 13 (174-216 MHz)
Band V – Channels 14 to 83 (470 to 890 MHz)
VHF and UHF VHFs (very high frequencies) arechannels that usually include channels 2 to 13. UHFs (ultra high frequencies) are channels that usually include channels 14 to 83.
Both VHF and UHF are great frequencies for carrying TV signals (both audio and video). They have a long range and can penetrate structures such as walls.
Higher Bands These bands are much higher in frequency and behave like light waves instead of radio waves. Structures usually obstruct these bands and they need a clear line of sight. Many satellite signals can use these frequencies, but require special equipment.
NTSC All standard television signals that are transmitted in the United States follow NTSC regulations. NTSC (National Television Standards Committee) states that the video signal must have a video line resolution of 525 lines with a 3.58 MHz chroma carrier (color TV signal) and must cycle at 60 cycles per second. It also states that frames are to be displayed at 30 frames per second. NTSC standards make it easy for all TV sets to pick up the same signals that broadcast companies transmit. It is important to note that this standard is for analog television only.
Frequently Asked Questions
Q: How can I pick up Over The Air (OTA) Digital and HDTV broadcasts?A: There are currently 3 ways to pick up your local stations:
An over the Air only digital receiver that will tune in only the local channels. A unit with HD outputs can be purchased at any electronics chain for about $99-$199. One advantage to this is there will be no monthly fees. Note: for $40 -$60, coupon eligible converter boxes will pick up the HDTV signals and down convert them to 480I in order to be displayed on an analog TV.
An HDTV with a built in OTA tuner. Note: All TVs made after 2007 should have an ATSC built in. (If your TV says “HD ready” it does not have a digital tuner built in).
An HD satellite tuner. Both Dish Network and Direct TV offer HDTV satellite receivers with the over the air tuner built into the same unit. The advantage of using this method is that there is no need to utilize separate equipment to receive premium HD networks like HBO HD and ShowTime HD. Also, the local and satellite channels can both be integrated into the program guide, to make it seamless for the viewer when switching between local and satellite. You will need an over the air antenna (like the ones we sell) as well as the dish connected to the receiver. These receivers can cost anywhere from $199- $499 although with specials & promotions it is often possible to find them for much less. (Note: some DirecTV units now require a separate ATSC tuning module)
Q: Are all Digital Channels on UHF?A: No, but currently (prior to June 2009), 91% of broadcasting DTV stations are on UHF. A few cities, such as Chicago and Las Vegas have DTV stations on VHF as well as UHF. While Many DTV stations are now occupying UHF broadcast channels, the plan will allow some broadcasters to move back to their original VHF or UHF TV channels once the transition to DTV is complete. After June of 2009: 74% of the DTV stations will be on UHF (14-51), 24% will be on high VHF (7-13) and less than 2% will be on Low VHF(2-6). For more information, please visit www.antennapoint.com.
Q: How is reception in distant or "fringe" areas? Will I get a fuzzy picture?A: When it comes to digital television, it's an "all or nothing at all" proposition. Once the signal is acquired, a steady stream of data assures you'll get a perfect picture and great audio. If that bit stream is interrupted, however, there will be nothing - just a blank screen. In areas with lots of buildings or obstacles, multi-path distortion can cause a "cliff effect" to kick in. The fix is to use a higher-gain antenna assuming the multi-path can be tamed. Work is being done to determine the optimal designs for improving error correction in set-top receivers.
Q: How do analog TV broadcasts and DTV compare to each other?A: There are some similarities. Both use VHF and UHF broadcast frequencies. While analog and digital television broadcasts have a modulated carrier wave, the way that signal is modulated is entirely different. Analog TV uses an amplitude-modulated (AM) signal for pictures and frequency modulation (FM) for audio, while DTV signals use digital "packets", to transmit pictures and audio.The modulation system currently being used for DTV in the United States is Eight Level Vestigial Sideband (8VSB). As Terrestrial Digital / HDTV broadcasts become more prominent, UHF antennas will play a larger role because the majority of the HDTV/Digital channel allocations will be in the UHF frequency band.
Q: Getting VHF stations are a problem for me. I get everything else fine.A: Many stations that have reverted to VHF assignments have dramatically cut their transmitter power, in some cases by over 90%! Some stations mistakenly thought they could save money by cutting their power while reaching the same number of viewers. In other cases the FCC imposed reduced power limits to stations that reverted to their old VHF assignments in order to prevent interference with adjacent markets. There has been a misperception among some station owners that while dramatically lowering DTV transmitter power, they could serve the same coverage area as analog, and this has turned out to be incorrect. Many stations who have reverted back to VHF are now finding themselves with significantly reduced coverage areas and fewer viewers after switching to VHF. Many stations realizing their mistake have applied for higher power assignments (or UHF channel assignments) from the FCC, but the process could take over a year. In the interim, a new high gain high VHF antenna, the Clearstream 5 will be forthcoming. This may replace on the receive side some of what has been lost. The Clearstream 5 has an expected ship date of late June 2009.One potential problem with re-using low VHF (2-6) and high VHF (7-13) TV channels for DTV is the possibility of interference from other signals during certain times of the year. "Skip" may bring in distant broadcasts on the same channel and create interference. Low VHF (2-6) digital broadcasts are particularly prone to interference and is often hard to receive reliably, regardless of what model of antenna is used. Note: The physical size of low VHF and high VHF antennas is much larger than that of a UHF antenna.
Q: What is a Yagi?A: The Yagi antenna is credited to Hidetsugu Yagi (although not the original inventor), A Japanese physicist. The Yagi was designed to improve the gain of the antenna concentrated in one direction. The directivity is accomplished with added elements called directors and reflectors. The Yagi has high Gain, is very directional, and has narrow bandwidth. In simple unidirectional antennas like the Yagi, frequency bandwidth is inversely proportional to antenna gain. One way to increase the frequency bandwidth of a simple antenna like a Yagi, is to increase the diameter of the antenna conductors. The greater the conductor diameter, the wider the band with increased conductor diameter also has a second benefit, it increases the physical strength of the antennas.
Q: What is the difference between UHF and VHF antennas?A: The most obvious difference between VHF and UHF antennas is the size. A half wave dipole for channel 2 will be 10 times longer than for channel 28. This means that a much more elaborate UHF antenna can be constructed without the antenna becoming physically unmanageable. With more elements added to the UHF antenna, higher gain and directivity can be obtained.
Q: What is the Bow tie Antenna?A: A bow tie antenna is another name for a UHF fan dipole antenna. By using triangular elements instead of rods, the bandwidth is greatly increased, to cover the entire UHF band. Additionally, the mesh reflector of the bowtie is more efficient than the rod reflector, Additionally, it is lower in weight and has less wind resistance.
Q: What is the Corner reflector Yagi?A: The corner reflector is a popular UHF reflector, that has a very high front to back pickup ratio; for reducing reception from the backside. This is particularly important if you don't want interference from stations to the rear of the antenna. The driven element is placed at the center of the corner angle that affects the power gain, directivity and impedance. Combined with Yagi type directors this increases the gain and directivity of UHF antennas over the entire UHF band.
Q: What makes the ClearStreams different?A: Whenever you design an antenna for a narrower range of frequencies you can expect dramatic improvements in performance. The Clearstream antennas are tuned specifically for the post 2009 core DTV channels. The ClearStreams are also less prone to interference and will insure better pulse fidelity than any other antenna on the market.
Q: My wife won't let me put one of these things on my roof. Can I install an antenna in my Attic?A: Yes you can, but keep this in mind. One layer of asphalt shingles + roof felt + ¾" plywood roof deck = 50% reduction in signal strength. Plus if you have metal or aluminum backed insulation in the walls or under the roof the signal will be most likely blocked. You'll have to remove the insulation or install the antenna in a different place. Although the antenna is inside, you'll still need to make sure that the narrow end points toward the transmitter of the TV station.
Q: My Homeowners association prohibits antennas on the roof, what can I do?A: Show them the Federal law concerning antennas, homeowners and their rights. In 1996, The FCC affirmed the rights of homeowners to place antennas on property they own or control.* Check out the FCC ruling here: http://www.fcc.gov/mb/facts/otard.html. The law basically states that homeowner association covenants cannot prevent you from installing antennas or dishes. The rule "prohibits restrictions that impair the installation, maintenance or use of antennas used to receive video programming." *Masts higher than 12 feet above the roofline may be subject to local permitting requirements.
Q: How far can I be from the transmitters and still get a good signal?A: Getting reliable UHF DTV reception beyond the curvature of the earth (approximately 70 miles) is difficult. The good news is that terrain has a major impact on reception. Going over water is about the best it gets, since water is generally flat and has positive impacts on temperature for sending the signal along. Still, beyond 70 miles, unless you can get direct line-of-sight to the transmitters, the number of things that could impact reception negatively is numerous. Just keep these in mind going in to the project. Accept that what you want may not be possible.
Q: I have read ads for an antenna that can pick up stations 200 miles away. Is this possible?A: Under extremely rare circumstances, a television antenna could possibly pick up stations 200 miles away. However, rarely is, an antenna going to get terrestrial television broadcasts over such a distance.Theoretically, it would be possible if you lived on top of a mountain and the broadcast towers were also on a mountain. At normal elevations, however, the curvature of the earth pretty much limits effectiveness to about 70 miles for UHF band signals. Low VHF band (2-6) can bounce further than this, but currently only about 7% of digital TV channels are on the VHF band. Most Digital TV channels are on the UHF band - which is line-of-sight transmission.
Q: What about "HDTV" antennas they sell at the electronic chain stores, won't these work?A: Some will, but very few of the antennas sold in electronic chain stores (except for ours) have much success with digital reception. They usually have poor gain on the frequencies where digital broadcasts occur and have a difficult time with multi path distortion. Most utilize low grade amplifiers that introduce noise on the line or are shaped to be aesthetically pleasing, but contrary to the principals of digital TV reception.
Q: My channels display as 2.1, 5.1, 7.1 etc. So I need a VHF antenna right?A: NO what you are looking at on your display is likely a re-map. If your analog station is broadcasting on a frequency assignment of say 2 then the digital broadcast will must be on a separate frequency as two TV stations cannot broadcast on the same frequency at the same time. For example the analog assignment for the KCBS in Los Angeles is Ch 2 and the digital broadcast will likely show up on a tuner as 2.1, but the digital frequency is actually 60.(changing after June 2009) Remember, the vast majority of digital broadcasts (74%) are on the UHF band. Find the true frequency assignment here: www.antennapoint.com
Q: I bought an HDTV set and my picture still looks the same even after I bought your antenna, and sometimes I see snow or fuzz. I know it's not the TV's fault because it was the top of the line. The salesman told me everything I needed is built into the TV.A: Many people (and a good number of TV salesmen) are not aware that that their older HD ready (pre-2007) sets may not have a digital tuner built in. If your owners manual or literature does not specifically state that an ATSC or digital tuner is included, then you will need to get an external set top box (ATSC HD tuner) which will run about $99-$199. The majority of large screen TVs (36” or larger) purchased after January 2006 have a built in tuner and almost all TVs regardless of size, sold since 2007, will have a digital tuner built in.