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In the early post-WWII era, home theater in all its initial black-and-white glory started with a screwdriver. In most cases, a Phillips screwdriver, which was needed to attach the flat 300 ohm twin-lead wire from outdoor antennas or classic indoor rabbit ear antennas to the two antenna reception screws on the back of televisions. (Note: Tin foil on the rabbit ears was always optional.)
The flat twin-lead wire housed two thin-gauge wires inside a single plastic ribbon. The wires ran from different parts of the antenna -- a left side and right side in the case of the aforementioned rabbit ears -- and ended with two u-shaped connectors that slid under the heads of the aforementioned screws on the backs of TVs.
The twin-lead 300 ohm wire was flexible and robust enough for the primitive job at hand. An ohm is a unit in the International System of Units or SI (abbreviated from the French Système international d'unités) to measure resistance. Represented by the Greek letter omega, an ohm is equal to one volt creating one ampere in a device, with an ampere or amp defined as a measure of current equal to a specific amount of force between a pair of infinite conductors in a vacuum. Ohm isn't an acronym. It's in honor of renowned early 19th century German physicist, Georg Ohm.
Turns out TV was a pretty popular technology, and a dozen channels weren't enough to satisfy demand.
Early post-war TV signals were transmitted in the very high frequency or VHF band, offering TV channels 2 to 13 in the frequency range generally between 30MHz and 225MHz. In the early days of television broadcasting, a thin pair of wires connected to an indoor or outdoor aerial antenna was all you needed to accommodate the bandwidth -- even with the advent of color broadcasts -- of those few channels.
Turns out TV was a pretty popular technology, and a dozen channels weren't enough to satisfy demand. The powers that be at the time couldn't possibly have foreseen the emergence of Snooki, the Kardashians and other "must-see" TV fare -- and if they had, they might have had good reason to impose Draconian measures to keep a cork on the TV technology bottle. But it was a simpler, slightly more innocent era. For good or ill, they expanded the TV menu. In 1952 the Federal Communications Commission allocated 70 more channels above the VHF band, this time in the ultra high frequency or UHF band delivering channels 14 through 83. You needed a better antenna – preferably an outdoor rig – to capture UHF signals. UHF signals collide more with atmospheric and environmental forces, and as a result UHF channels suffer more from visual "snow" -- grainy picture -- and "ghosts," multiple images caused by a signal arriving from two or more directions simultaneously bounced off buildings, hills, trees and what have you.
In any case, twin lead-in antenna wires, with their thin insulation and construction, often had trouble with signal degradation, particularly when exposed to the elements. Sun, salt, moisture and Father Time tended to take their collective toll on this species of TV connection. We needed something better.
An Englishman named Oliver Heaviside invented coaxial cable in 1880. But he never lived to see it become the standard television connector of the latter mid-20th century. Coaxial, or "coax" for short, remains the primary television connection into your tuner, be it from your satellite antenna or from your cable provider. It's like the container ship for encoded TV signals, which are unloaded, decompressed and decoded at digital set-top boxes.
"Coax is basic," notes Geek Squad Agent Ismael Matos, "but it's still capable of quite a lot."
Coaxial (also known as radio frequency or RF) cable has two conductors -- a center core wire and a mesh or braid of copper or aluminum -- and a foil sheath separated by a dielectric (plastic) material all housed in a single outer plastic jacket. The wire attaches to televisions and other electronic devices with a single jack -- most often with an F screw connector, sometimes a Bayonet Neill-Concelman or BNC slip-on connector or even RCA plugs (more on those in a bit). Coax can ferry more video and audio bandwidth with less signal loss or leakage than twin-lead wires. How much loss depends on the quality and length of the coax.
Most coax cables geared for today's electronics are designated RG, followed by a number. RG stands for radio guide and was a unit indicator for bulk RF cable used by the military. Numbers were assigned sequentially to RG coax as materials improved to keep in step with increasing bandwidth demand. RG 59, for instance, was the standard for cable television installations beginning in the '70s. RG 59 still often comes standard issue with retail electronics. It's thinner, cheaper and more flexible than better breeds of coax and can bend around sharp corners and slip inside tighter spaces. It has a diameter of 0.242 inches, about as thick as a pencil. But what it makes up for in slithering ability, it loses in signal degradation compared to RG 6 coax, today's typical coax cable of choice. For every 100 feet, RG 59 loses 12 dB of signal when measured at 1,000MHz or 1GHz.
Your RG 6 cable has a diameter of 0.265 inches and carries signals longer distances without as much signal loss as RG 59. RG 6 loses about 6.1 dB per 100 feet at 1GHz -- essentially twice as the performance of RG 59. And RG 6 still is bendable enough for certain home theater connections.
But you should know that not all RG 6 coax cables are created equal. RG 6 is more or less a generic term for coax cables that typically have aluminum (rather than copper) foil sheaths and an 18 American wire gauge or AWG copper center conductor with a 75 ohm characteristic or surge impedance. (By the way, the lower the gauge number, the thicker the wire
.) Some RG 6 coax cables have thin, flimsy aluminum conductor mesh and an 18 AWG copper-coated steel center conductor -- not all that awesome. Or,
you could have an RG 6 coax with so-called quad shield mesh -- better, but not the best. Or you could have a precision serial digital video coax, something with a dense mesh and twin-foil shield, a solid copper 18 AWG center conductor and what the folks at Blue Jeans Cable
note has a "nitrogen-injected PE foam dielectric, and extremely broad bandwidth and tight impedance tolerance." They're fond of the Belden 1694A 4.5GHz precision coax cable, by the way -- it's the preferred coax for broadcast studios and high-performance home theater applications, according to Belden, and "provides large head-room for future high-bandwidth cable TV, satellite and HDTV." You can buy it bulk in lengths of 500 and 1,000 feet, or pre-cut lengths of 6, 10, 25, 50, 75, 100 and 150 feet.
Don't use coax to connect your TV to disc players, game consoles and other peripherals. Coax offers the lowest resolution among today's connectors.
And, no, we're not forgetting RG 11, another 75 ohm coax cable. It's just that at a whopping 0.405 inches in diameter, RG 11 is practically an unbendable rod, thus impractical for home theater use. It's good for when you have to connect, say, a satellite antenna that's more than 100 feet away on a run without a lot of bends. For the record, RG 11 loses 5.6 dB for every 100 feet when measured at 1 GHz -- not that great of an improvement over RG 6, really.
What's yellow, red and white and delivers ho-hum video quality and so-so audio? Why, analog video composite connectors and their analog audio lines, of course. You'll likely find as many of these yellow, red and white RCA jacks -- if not more -- than any other type of slot on some TVs, and they're one of the main culprits of cable cluster. RCA jacks are named after the Radio Corporation of America company, which introduced the technology in the 1940s to connect phonographs (record players) to amplifiers. That's why they're also known as phono plugs -- not to be confused with phone plugs that use TRS (tip, ring, sleeve) connectors. We'll leave aside for the purposes of this discussion TRS connectors, typically used for audio.
More often than not, yellow composite video lines are coupled with red and white lines for right and left audio jacks, respectively. The ubiquitous cables are noted for their single male pins and colored collars and the color-matching jacks. Because we mentioned audio, we should note that while high-definition TVs excel with visual, they often want for better sound. Home theater buffs may find it worth their while to invest in a digital audio system. But as in the case with TRS, we'll leave the digital audio topic for another day.
The max video resolution of composite video is 480i, which is 720 x 480 pixels at 59.94Hz. The "i" in 480i stands for interlaced, where TVs draw every other horizontal picture line and then loop back and draw the remaining lines -- 1, 3, 5, 7 ... then lines 2, 4, 6, 8, and so on. Most cable and satellite TV providers transmit high-definition digital signals at 720p, with the "p" defined as progressive scan, with each horizontal line drawn sequentially at about 60 Hz. Progressive scan is generally crisper than its interlaced counterpart. As of June 12, 2009, over-the-air analog TV transmissions ceased
in the United States and broadcasters switched
to digital. Composite connectors aren't really up to the task of today's bandwidth loads. Unlike better types of connectors, composite video doesn't separate colors and brightness into distinct channels.
You'd like to think TV manufacturers would have phased out composite video by now. But PlayStation 3, Wii, some disc players and other electronics still support this connector.
Colors and brightness or luminance are shoved through one hose, so they tend to run together and lack that hi-def visual snap, crackle and pop of high-end digital transmissions. Composite video also is notorious for dot crawl, the checkerboard pattern that afflicts images when color and brightness are muddled due to imprecise multiplexing or blending of signals through a single medium.
You'd like to think TV manufacturers would have phased out composite video by now. But PlayStation 3, Wii, some disc players and other electronics still support this connector. Even devices that accommodate HDMI (we'll get to this soon) often come packaged with composite cables, sometimes making them tempting to use for the cost-conscious. So we expect this techno-holdover to linger. Sigh.
Of note, don't use coax to connect your TV to disc players, game consoles and other peripherals. Coax offers the lowest resolution among today's connectors. Coax connections should only be used to connect your audio / visual system from an outside source such as antenna, cable or satellite.
S-Video -- with the "s" standing for super or separate depending on whom you ask -- delivers better image quality than composite video, but it still belongs in the technological rear-view mirror. Sure, this analog rig encodes video into separate color and luminance channels, making for a cleaner picture capable of 480i resolution. It had its heyday in the '90s, when game consoles, DVD players and certain home theater devices used this optional connection because of its better video quality than composite video. There's a good chance the next high-def TV you buy won't even have this connection option. Beyond its subpar video throughput compared to newer technologies, it only handles video. You still have to run audio connectors, which contributes to cable clutter.
S-Video cables are multiwire analog connectors. They encode and synchronize video information in Y or luminance and C or color transmissions. They typically come with four pins for the Y and the C signals, each with their own ground. Packing S-Video color information in one signal requires encoding that data, and not all S-Video compatible devices encode S-Video video in the same way. Another S-Video bummer: it offers 120 horizontal lines of resolution; a commercial DVD has up to 540 horizontal lines of resolution. You do the math.
Video Graphics Array or VGA connectors are great for turning your high-def, flat-screen TV into a giant, over-priced computer monitor. VGA cables, easily identified by their three-row, 15-pin connector, carry analog component red, green, blue and horizontal and vertical video signals. These cables typically connect a computer's video card to a monitor. For those using VGA on TVs, you'll have to get your audio elsewhere -- again adding to cable clutter.
We saw these connectors on brand new sets on sale this holiday season, including the Sony Bravia
54.6-inch LED EX720 Internet and 3D capable television. You'll also see this type of connection labeled "RGB" on some TVs. You can get high-definition analog video up to 2,048 × 1,536 pixels @ 85Hz (388 MHz) transmitted at 1080p through VGA cables on your TV screen. For this reason, VGA hookups can be a better alternative than high-definition component video connectors (addressed below) because of anti-piracy technology Hollywood studios are able to embed in Blu-ray Discs. By using High-bandwidth Digital Content Protection (HDCP) technology, studios can insert Image Constraint Token flags into Blu-ray Discs, though these require a logo on the packaging and to date have yet to be used in the mass market. Hollywood studios maintain that analog video is easier to pirate than digital video. When a Blu-ray Disc player detects an analog component video connection that doesn't support high-bandwidth protection technology, it can downgrade a video's 1080p all the way down to 540p -- still higher than 480p, which is DVD-quality video. The thinking goes that the lower the video quality, the less incentive to pirate. The truly motivated and ambitious usually always find ways to crack digital rights management and anti-piracy codes, and, indeed, the high-bandwidth protection technology already has. VGA cables present a hardware work-around to Hollywood.
Yet other than TVs, desktop and laptop computers, you may have to search high and low to find other types of electronic devices with VGA jacks. You can fight "the man" with VGA / component video converter cables -- attach the VGA (or RGB) end into your TV and plug the component video ends into your Blu-ray Disc player (or whatever else).
This is common knowledge in A/V circles, but of the three main consumer analog video connection formats, component video is better than composite and S-Video. Component video separates and synchronizes the colors and brightness levels, resulting in far less signal loss and delivering better image quality than composite and S-Video. High-end component video cables are designed for extreme bandwidth, in some cases 100 times the bandwidth required for 1080i high-definition component video. While component video is capable of a max resolution of 1080p, many devices as indicated above will top out at 1080i when using component video connectors. Again, interlaced, with its alternating, non-sequential horizontal line display may appear a little choppy compared to images displayed at 1080p. If you can tell the difference, we'll take you at your word.
Component video connectors are green, blue and red; the cables often are bundled with red and white audio lines; and they use RCA male ends and female slots. We know there are other types of component video, but the green / blue / red type with the RCA connectors are what most of us think of when we hear "component video." In the patois of TV, component video cables sometimes are called yippers after the YPBPR color space in video electronics. It's the analog version of YCBCR. for digital video. Some TVs list both designations under each colored jack. YPBPR is converted from the red, green and blue or RGB color model -- the primary colors in video display -- used to create the vast catalog of other visible colors. The Y is the green connector, which carries brightness or luminance (luma, for short) and color synchronization data. The math looks like this: Y = 0.2126 R (red) + 0.7152 G (green) + 0.0722 B (blue). PB/CB is the blue connector that ferries the difference between blue and luma or B – Y. And PRCR hauls the difference between red and luma or R – Y. There's no need to send green because the blue, red and the brightness can create that hue.
You're still talking three analog cables and connection ports, when you could be using just one digital cable for video and audio.
At the outset of the 21st century, the industry consortium known as the Digital Display Working Group rolled out digital video interface, or DVI, as the heir apparent to VGA and the preferred means to transmit high-definition analog and uncompressed digital video among devices. It didn't take long (May 3, 2006) before another industry body, the Video Electronics Standards Association, unleashed DisplayPort
, designed to replace DVI and capable of transiting both audio and digital video. We'll skip the tech specs on both DVI and DisplayPort because in the HDTV market, they're mostly
irrelevant. Another connection technology, high-definition multimedia interface (or HDMI
) launched in 2002 and has become the de-facto standard connection for high-definition digital video and audio. Single HDMI cables and ports are now used with set-top boxes, Blu-ray and DVD players, laptops, desktops, tablet computers, computer monitors, game consoles, camcorders, cellphones and, of course, digital televisions. With an adapter, the 19-pin HDMI connection is backward compatible with DVI with no signal conversion and, thus, no loss in video quality.
HDMI cables and ports are now used with set-top boxes, Blu-ray and DVD players, laptops, desktops, tablet computers, computer monitors, game consoles, camcorders, cell phones and, of course, digital televisions. With an adapter, the 19-pin HDMI connection is backward compatible with DVI with no signal conversion and, thus, no loss in video quality.
There are five HDMI connector types. Type A/B are defined in the HDMI 1.0 specification; Type C is the HDMI 1.3 specification; Type D/E are HDMI 1.4 specification. All the HDMI connectors (including mini HDMI connectors for portable devices) used in today's HDTVs have 19 pins; Type B has 29 pins and can carry double the video bandwidth of type A HDMI connectors. Type B connectors may find use in super-high resolution displays such as those with 3,840 x 2,400 pixels, but it hasn't been plumbed into commercial electronics... yet.
All told, there have been some half-dozen iterations of HDMI
, with the latest being HDMI 1.4b released in October 2011. This one packs a lot of punch. Let's run through some of the specs. HDMI 1.4b allows a maximum resolution to 4K × 2K, such as 3,840 × 2,160p (Quad HD) at 24Hz / 25Hz / 30Hz or the digital theater resolution of 4,096 × 2,160p at 24Hz. So that 4K x 2K broadcast from the London Olympics you may have heard about
? HDMI 1.4b will be up to the task. It has a maximum clock rate of 340MHz with a maximum transition-minimized differential signaling throughput per channel of 3.4 gigabits per second with 8b / 10b overhead, with a total maximum throughput of 10.2Gbps. Max audio throughput is 36.86 megabits per second, complemented with a maximum color depth of 48 bits per pixel. It also supports audio return channel and a variety of 3D display formats -- 720p50 and 1080p24 or 720p60 and 1080p24 -- as well as Ethernet Channel capable of a 100 Mbit/s Ethernet connection between devices hooked to the Internet.
All iterations of HDMI 1.4 accommodate sRGB, YCbCr, eight channel linear pulse-code modulation 192 kHz, 24-bit audio, Blu-ray disc and high-definition DVD video and audio at full resolution and Consumer Electronic Control. Latter versions of HDMI support Super Audio CD, Deep Color, xvYCC, auto lip-sync, Dolby TrueHD and DTS-HD Master Audio.
And all of this in a single cable.
"HDMI is the key connector," says Ismael Matos, the Geek Squad Agent. "It simplifies everything. You can have three components, Blu-ray, a game console and a set-top box, and it's only going to take three cables. If you go the component (video) route, you can go from three cables to 15 very quickly. And because component video connections are analog, you can still get a digital signal with crosstalk interference."
In short, HDMI hits all the right notes: industry support, ease of manufacture and installation, and consumer acceptance.
HDMI Founders developed and successfully evangelized this format. Its members are Hitachi, Matsushita, Philips, Silicon Image, Sony, Thomson and Toshiba. The HDMI Licensing LLC group oversees the HDMI standard -- any HDMI cable from any manufacturer can work on any HDMI-supported device without signal-loss issues. HDMI, and it's HDCP protection, has the full blessing of Hollywood -- Disney, Fox, Universal and Warner Bros. support it -- as well as system operators CableLabs, DirecTV and Dish.
In short, HDMI hits all the right notes: industry support, ease of manufacture and installation, and consumer acceptance. The only downside to HDMI may be the fragility of the 19 male-end pins – bend one of those and you'll have to buy a new cable -- and the sometimes hassle of aligning the male and female ends, particularly with wall-mounted TVs with jacks on the back. Furthermore, HDMI has been lambasted for "falling out" and has been prone to retailers overcharging for cables, but the latter can certainly be avoided by shopping at places like Monoprice
Despite our love affair with HDMI, we still long for something even better, something more in keeping with our always connected, location-obsessed culture. We'd love for all our electronic devices to be networked via wireless. No cables at all. Many new TVs support the IEEE 802.11a/b/g and n communication protocols, with IEEE 802.11n
often the preferred format -- video over IEEE 802.11b/g connections may not play as smoothly. What about security? There's WEP, WPAPSK and WPA2PSK authentication modes, with WEP, TKIP and AE encryption types. We do this for public WiFi, certainly we can do it for home theaters. And bandwidth? Ah, bandwidth. Modern hardwire connectors can transmit up to 10.2Gbps. Cable modem speeds vary widely, but conventional home connections are currently capable of hitting speeds of around 105Mbps
. The WiFi connection speed from a cable modem in one of our homes exceeded 10Mbps. Like the goldfish that grows to the size of its bowl, bandwidth has a way of growing to the size of its medium. The wireless bandwidth gap can be closed. And it will, eventually.
Despite the proliferation of jacks and ports behind and on the sides of new TVs, it doesn't take a genius to figure which cables go with which connectors. Some TVs even color outline and label "Best," "Better" and "Good" jacks and ports, with HDMI always earning the "Best" designation. From a single input -- the UF antenna -- to a population explosion of TV connector formats, we may be headed back to simpler times. HDMI handles digital, hi-def duties for video and audio.
The double duty HDMI performs in a single, precision-performing, thin and pliable cable reduces the number of jacks and ports needed on TVs. Why did they have to make HDMI ports so awkward? Hard to say. The male and female ends never seem to want to align initially and it usually takes some fiddling to get everything snug. But once HDMI's snapped into place, you have entrée to the best digital video and audio current HDTVs have to offer.