Television from beyond the heavens - Soundings Online

Television from beyond the heavens

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Most of us obtain a great deal of our news and entertainment from television, and being on a boat does nothing to change this habit/preference.

Most of us obtain a great deal of our news and entertainment from television, and being on a boat does nothing to change this habit/preference. We

expect to have access to clear, interference-free, stable color images — preferably in high definition (HDTV) — and view them on 16-to-9 aspect ratio screens capable of 1,080- or, at the minimum, 720-line resolution (complete with “5.1” surround sound). However, unless we are connected to a cable TV system at a dock or are in a location where an on-board antenna can deliver local broadcast television stations, we will have to access one of the satellite TV providers (DIRECTV or Dish Network in the continental United States and adjacent waters).

Snatching the signal

The equipment required to receive and decode the signals from television broadcast satellites at fixed, terrestrial locations is highly developed and quite inexpensive — when you subscribe to a long-term service contract. However, the equipment required to keep an antenna on a boat precisely aimed at a satellite orbiting the earth at an elevation of 19,317 nautical miles is very different and more expensive. Fortunately, the combination of markets for satellite TV in recreational vehicles and on large yachts has spurred the development of a number of satellite TV systems, some small enough to be practical for just about any boat with an enclosed cabin in which the television screen can be comfortably viewed.

The relatively low power of the satellite signal when it reaches the earth and the desire to minimize receiving antenna size requires the use of a sharply focused or narrow-beam antenna that must be aimed at the satellite with an accuracy of plus or minus 2 to 3 degrees in both elevation and azimuth. Achieving this degree of accuracy and stability when the antenna is on a floating object can be a significant challenge, as you no doubt know from trying to keep your binoculars trained on an object when under way or even when anchored and subject to the wake from a passing boat.

The on-board performance of a satellite TV system is largely determined by the precision and agility of the antenna pointing system, the efficiency of the antenna, and the performance of the Low Noise Block (LNB), the device at the antenna that converts the 12 GHz, Ku band signal broadcast from the satellite to the 1.5 GHz, L band signal that is sent from the antenna to the satellite receiver below deck.

The two aspects of satellite tracking are determining the appropriate elevation angle and the correct azimuth angle (with reference to magnetic or true north). For boats at anchor in relatively protected waters the primary antenna alignment challenge is azimuth tracking, keeping the antenna accurately pointed as the boat swings around.

The tracking problem becomes increasingly severe if the boat is rolling or pitching, requiring compensation in the elevation axis. Forward motion of almost any magnitude adds significantly to the challenge, requiring quite rapid response from the servomechanism that controls the position of the antenna, which limits some satellite receiving systems to use only when the boat isn’t under way. Fast sportfishing boats pose particularly challenging problems, especially when the satellite antenna is located high above the deck on the tuna tower. (Special antenna systems are available for this application.)

On the water, not moving (much)

Television reception while at anchor in protected waters poses the smallest challenge, since it could be possible to obtain satisfactory results using a single-axis, azimuth-only, automatic-tracking mount that supports a standard terrestrial satellite TV antenna. The required elevation angle is set manually, primarily by reference to the vessel’s latitude. The antenna is then rotated to the compass heading that brings the satellite into view. Once this is accomplished, systems such as Track It TV will stabilize the antenna’s azimuth angle with reference to their integral electronic magnetic compass. Once locked on the desired heading the antenna will continue to point on the selected heading — it doesn’t track the signal from the satellite — with a claimed accuracy of plus or minus .1 degree in relatively calm conditions.

Keep in mind that the antenna mount’s tracking ability is limited to 720 degrees. The system will have to be reinitialized if the boat eventually swings through a greater arc. This system offers a relatively low equipment cost and zero installation cost — it clamps to a rail in a few minutes — and can do the job when used in reasonable conditions.

An alternative solution is the KVH M2, a dome-enclosed antenna system that will actively track the satellite in both elevation and azimuth. However, the tracking system used in this model will perform satisfactorily only when the vessel is anchored or moored, according to KVH.

TV under way

The majority of boat owners want a television system that will automatically acquire and track satellite signals both at anchor and when under way. Such systems are now available in packages small enough to be used on boats in the 20-foot range. As with any satellite receiving system, the signal-gathering ability of the antenna depends on its size (bigger is generally better) and ability to precisely and efficiently focus the received signal energy and deliver it to the system’s front-end electronics.

Not long ago such systems were quite large, requiring antennas that measured a few feet in diameter. Fortunately, developments in antenna design and tracking system response and accuracy, as well as improvements in receiver electronics, make it possible for antennas barely more than a foot in diameter to provide excellent results in coastal and near-shore waters out to more than 100 miles in some cases.

The typical 15-inch antenna assembly weighs less than 20 pounds and is relatively easy to install. The system power consumption is modest, usually less than 60 watts (5 amps at 12 volts). For most systems, only a single cable connection is required between the antenna assembly and the below-deck interface box.

The least costly automatic systems are derived from units initially designed for use on vehicles. The KVH TracVision C3 is typical of this type of equipment and is housed in a 32-inch-diameter, 14.5-inch-tall radome enclosure. The system can be used to view programs transmitted in HDTV and can track while the boat is under way in moderate sea conditions. Street price for the TracVision C3 is about $1,650. The relatively large footprint of the antenna, however, may pose installation problems on smaller boats. A similar system is available from Sea King (model 9762-SW) in a 28-inch-diameter, 15-inch-tall dome ($2,400).

Satellite TV systems designed specifically for boats and yachts are available from a number of suppliers, including KVH (www.kvh.com ), Sea Tel (www.seatel.com), Sea-King (www.kingcontrols.com) and Raymarine (www.raymarine.com ). These systems employ agile, automatic signal-tracking antennas and are housed in the familiar dome-type enclosures with diameters as small as 15.5 inches (and as large as 32 inches).

The KVH product line includes three 14.5-inch-diameter models. The M2 is lowest in cost at about $2,400, but as noted above it is usable only when the boat is not under way. The M3ST ($3,300) and M3DX ($4,000) can be used under way, with HDTV service available with the M3DX. The M2 and M3ST will operate with satellite providers that serve North America, while the M3DX also can be used in Europe and Central America. KVH’s 18-inch M5, 24-inch M7, and 32-inch M9 can be used in North America, Central America, South America and Europe. The 30-pound M5 is available with an integral gyro-stabilized compass, making the system usable when operating in the severe-motion environment created when it is installed on tuna towers ($5,900).

The Sea Tel Coastal 14 ($3,400) can be used to view HDTV programming. Sea Tel also offers the 20-inch dome diameter Coastal 18 ($4,800), as well as larger systems. The 16-inch-diameter, 17-inch-tall Sea-King 9815 can receive HD programming ($3,100). Sea-King’s 9818-RJ houses its 18-inch-diameter dish antenna in a 20-inch-diameter, 21-inch-tall dome ($3,300). Raymarine’s satellite TV systems include the 45STV (HD capable version also offered) — using a 45-centimeter-diameter (18-inch) dish housed in a 19.2-inch-diameter, 20.8-inch-tall dome ($4,200) — and the 60STV (HD available), using a 60-centimeter (24-inch) dish ($5,800).

If your plans for on-board television include multiple televisions, each able to select channels independently and located in widely separated locations, you will be best served to obtain the equipment and the installation from a competent marine electronics installation and service company. Its assistance also will prove invaluable should you decide to voyage to distant locations outside the main U.S. service area.

The coverage provided by each satellite TV provider can be determined from maps posted on their Web sites. The map may show the average signal strength at various locations, or it may use contour lines to indicate the area of coverage for various receiving antenna sizes. In the main coverage area a 14-inch-diameter antenna will provide acceptable signals over much of the 48 states and in nearby coastal waters. Depending on the selected service coverage, DIRECTV’s and Dish Network’s U.S. service may be less satisfactory in the upper Northeast states and Canadian Maritimes.

A service contract with one of the satellite providers will be required, since all TV satellite signals are encoded and can be viewed only when the receiver is provided with the proper decoding key. It’s important to check with the provider if you wish to watch programs that originate from local television stations. If you have a satellite TV system at your home you likely will be able to receive the local stations as long as you are in the home area. (Locally originated programs are transmitted on very narrow “spot beams” and cover limited areas centered on the city in which you live.) Check with the satellite company to determine if you will have access to local programming in other areas you might visit.

The service situation also could be different if you don’t have a home satellite system, since a phone connection usually is a required part of the service contract. If you plan to use your boat in areas remote to your home base, it’s important to check with the service provider about the availability of local channel service, since the contract might not include local stations and could impose higher charges for certain types of programming.

The signals from the TV satellite might include audio-only programs, such as the selected XM Radio programming on DIRECTV and the Sirius audio programs on Dish Network. Satellite TV can be viewed on multiple televisions, and with additional equipment different programs can be viewed on each set.

Obtaining HDTV coverage may pose problems with some systems, since not all satellites are broadcasting in this format. For example, HDTV programming from DIRECTV is at present available only from the Ku band transmitter on the satellite located at 110 degrees west.

Once you have your on-board TV system up and working, remember that it is normal to briefly lose signals when extremely heavy rain attenuates the signal or if water accumulates on the surface of the radome. Keeping the surface clean, possibly also using a rain dispersant to minimize the formation of large drops of water on the radome surface, might help.

Happy viewing. But please remember, watching television can be dangerous to your health and that of others, if the program is being viewed by the person operating the boat.

Chuck Husick is an electronics engineer who runs his own consultancy in the marine and aviation fields. A former chairman and president of Chris-Craft, he holds a Coast Guard 100 ton license, sails a 46-foot Irwin ketch and is a commercial pilot/ flight/instrument instructor.