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The main advantage of a portable television over other types of television is that it is designed to be portable; it is, or should be compact and light enough to be carried easily from room to room within your home, or transported to a holiday home or caravan, for example, robust enough to withstand being carried about, and offer the capability of operating away from a mains power supply for a reasonable length of time. This of course, overlooks the main functions of any television set; to provide high quality moving pictures and sound for entertainment purposes.
Early portable TVs however, were hamstrung by inferior A/V (“Audio/Video”) and battery technology, and most of all, by the requirement for a CRT (“Cathode Ray Tube”). A CRT is a specialised vacuum tube, in which an image is created by a beam of electrons previously known as “cathode rays”, illuminating a phosphor coating, making early portable TVs bulky, heavy and very deep.
The advent of LCD (“Liquid Crystal Display”) technology and the latest battery technologies (including “Li-Ion”) however, mean that these limitations are very much in the past. Modern portable TVs are typically available in screen sizes ranging from 6″ to 21″. Even the largest of these weighs in at around 20kgs, or 44lbs, and are capable of operating on rechargeable batteries for up to 6 hours. Not only that, but many of the useful features only previously seen in larger televisions (high quality, “Nicam”, stereo sound, for example) are being incorporated into the latest portable TVs.
Portable TV Features, Benefits & Considerations
Portable TV Size & Aspect Ratio
The size of a portable TV appropriate to your circumstances is likely to be dictated largely by where it is to be positioned, the number of people that are likely to want to watch it at any one time, and how often it needs to be moved from place to place. A handheld, 6″ portable TV screen is likely to be suitable for viewing by a single person, almost anywhere, but for a group of viewers a 12″, 14″, 17″, or larger screen may be more appropriate. Bear in mind that the diagonal measurement of the screen, as is customary, means that a relatively small increase in the quoted screen size can produce a relatively large increase in the overall viewing area available; the 3″ difference between a 14″ and a 17″ screen for example, results in a 20% increase in viewing area. Smaller, portable LCD TVs are much slimmer and lighter than traditional CRT TVs, but also offer some advantages when compared with larger, flat panel TVs. Smaller screens mean that portable TVs draw less current, and are more energy efficient, and if you want to mount your portable TV on a wall for example, mounting brackets for smaller TVs are available at a fraction of the cost of those for larger models.
Related to the physical size of a portable TV screen is the concept of “aspect ratio”. Aspect ratio is the proportional relationship between the width of an image (or indeed, a screen on which an image is displayed) and its height, expressed as a ratio. Traditional television screens, for example, have an aspect ratio of 4:3, or 1.33:1, such that the image displayed is 4 units wide for every 3 units it is high, or almost square. Modern portable TVs may, however, be designed to display true “widescreen” footage, shot with a wide-angle lens, with an aspect ratio of 16:9, or 1.78:1. In many cases, it is possible to select either a 4:3, or 16:9, aspect ratio on a portable TV, so that standard or widescreen pictures can be displayed correctly, without the appearance of black lines to the top and bottom (“letterboxing”) or to the left and right (“pillar boxing”) of the screen.
Portable TV Connectivity
You also need to decide what you want to do with a portable TV. This may sound like a statement of the obvious, but even if a portable TV is to be used in a domestic situation, it is unlikely that it will exist in isolation. Even if it does, you may want to watch “Freeview”, free-to-air digital television channels, in which case you need to look for a model that includes a integral Freeview tuner. Some portable TVs (known as “combi” or combination, portables) also include integral DVD or VCR (“Video Cassette Recorder”) components, which require no additional wiring or tuning and are inexpensive compared to the cost of buying the individual components separately.
Otherwise, you may want to connect digital devices such as DVD players, digital camcorders or games consoles, or you may want your portable TV to double as a computer monitor as some point. If this is the case you need to look for a range of connection interfaces (Composite, SCART, S-Video, VGA, etc.) appropriate to the devices that you wish to connect. A USB (“Universal Serial Bus”) port, preferably latest specification USB 2.0, offering data transfer speeds up to 40Mbps (“Megabits per second”) can also be some of the small, handheld models include an optional GPS (“Global Positioning System”) interface, for use with vehicle satellite navigation systems.
Digital & High Definition TV
As you are probably aware, the so-called “digital switchover” is scheduled to take place by in the United Kingdom, region by region, between 2008 and 2012. This means that traditional, analogue television broadcasting will cease, and be replaced by digital broadcasting instead. This has implications for analogue portable TVs need to be converted to digital, or replaced, if digital signals are to be received.
With all but a few exceptions, conversion to digital can be accomplished by connecting a TV to a digital box via a SCART lead, or, in the absence of SCART, via an RF (“Radio Frequency”) aerial – provided that the digital box has an integral “RF modulator” – but portable analogue TVs do seem to have been overlooked in the switchover process.
All of the digital converter boxes on the market require a mains power supply, which automatically negates the portability of a portable analogue TV; plainly, even if the TV itself, is capable of operating independently, it cannot receive digital signals other than through the digital converter, which needs to be plugged in. There appears to be no “quick fix” for this problem, and there is every chance that portable analogue TVs (certainly those that are used in a truly “portable” sense) may become obsolete in the not too distant future, and may simply be replaced by more affordable digital versions.
Many analogue portable TVs are however still available, and their price is likely significantly as the process of digital switchover gathers momentum. Digital portable TVs of the handheld or pocket variety are, however, available from around £60, while larger digital portable TVs (14″ and upwards) start at around £100, and represent a better, “future-proofed” investment. In the United Kingdom, a special logo known as the “digital tick” has been developed, to help consumers identify digital portable TVs, and other digital TV products, that are designed to work through the digital switchover.
With regard to HD, or “High Definition”, TV, many consumers are confused by the various terms used to describe the technology, and in particular the difference between “HD Ready” and “Full HD”. By way of clarification, all HD Ready TVs are capable of displaying pictures at 720p, or 1080i; that is, 720 horizontal lines using “progressive” scan, or 1,080 horizontal lines using the slightly inferior “interlaced” scanning technique, both of which provide significantly higher picture quality than standard TV, with 576 horizontal lines. Full HD TVs on the other hand, have a resolution of 1,920 x 1,080, and are capable of displaying pictures at 1080p. This means that an image is composed of 1,080 horizontal lines, laid down sequentially in one, single pass (as opposed to the two passes required by interlaced scanning) and is sharper, clearer, and flicker-free. 1080p however, is not used by HDTV broadcasters, but is used by the latest, high capacity disk technologies such as Blu-ray Disc™.